/src/postgres/src/backend/utils/adt/datetime.c

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/*-------------------------------------------------------------------------
 *
 * datetime.c
 *    Support functions for date/time types.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/datetime.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <limits.h>
#include <math.h>

#include "access/htup_details.h"
#include "access/xact.h"
#include "common/int.h"
#include "common/string.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "parser/scansup.h"
#include "utils/builtins.h"
#include "utils/date.h"
#include "utils/datetime.h"
#include "utils/guc.h"
#include "utils/tzparser.h"

static int  DecodeNumber(int flen, char *str, bool haveTextMonth,
             int fmask, int *tmask,
             struct pg_tm *tm, fsec_t *fsec, bool *is2digits);
static int  DecodeNumberField(int len, char *str,
                int fmask, int *tmask,
                struct pg_tm *tm, fsec_t *fsec, bool *is2digits);
static int  DecodeTimeCommon(char *str, int fmask, int range,
               int *tmask, struct pg_itm *itm);
static int  DecodeTime(char *str, int fmask, int range,
             int *tmask, struct pg_tm *tm, fsec_t *fsec);
static int  DecodeTimeForInterval(char *str, int fmask, int range,
                  int *tmask, struct pg_itm_in *itm_in);
static const datetkn *datebsearch(const char *key, const datetkn *base, int nel);
static int  DecodeDate(char *str, int fmask, int *tmask, bool *is2digits,
             struct pg_tm *tm);
static char *AppendSeconds(char *cp, int sec, fsec_t fsec,
               int precision, bool fillzeros);
static bool int64_multiply_add(int64 val, int64 multiplier, int64 *sum);
static bool AdjustFractMicroseconds(double frac, int64 scale,
                  struct pg_itm_in *itm_in);
static bool AdjustFractDays(double frac, int scale,
              struct pg_itm_in *itm_in);
static bool AdjustFractYears(double frac, int scale,
               struct pg_itm_in *itm_in);
static bool AdjustMicroseconds(int64 val, double fval, int64 scale,
                 struct pg_itm_in *itm_in);
static bool AdjustDays(int64 val, int scale,
             struct pg_itm_in *itm_in);
static bool AdjustMonths(int64 val, struct pg_itm_in *itm_in);
static bool AdjustYears(int64 val, int scale,
            struct pg_itm_in *itm_in);
static int  DetermineTimeZoneOffsetInternal(struct pg_tm *tm, pg_tz *tzp,
                      pg_time_t *tp);
static bool DetermineTimeZoneAbbrevOffsetInternal(pg_time_t t,
                          const char *abbr, pg_tz *tzp,
                          int *offset, int *isdst);
static pg_tz *FetchDynamicTimeZone(TimeZoneAbbrevTable *tbl, const datetkn *tp,
                   DateTimeErrorExtra *extra);


const int day_tab[2][13] =
{
  {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0},
  {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0}
};

const char *const months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec", NULL};

const char *const days[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday", NULL};


/*****************************************************************************
 *   PRIVATE ROUTINES                            *
 *****************************************************************************/

/*
 * datetktbl holds date/time keywords.
 *
 * Note that this table must be strictly alphabetically ordered to allow an
 * O(ln(N)) search algorithm to be used.
 *
 * The token field must be NUL-terminated; we truncate entries to TOKMAXLEN
 * characters to fit.
 *
 * The static table contains no TZ, DTZ, or DYNTZ entries; rather those
 * are loaded from configuration files and stored in zoneabbrevtbl, whose
 * abbrevs[] field has the same format as the static datetktbl.
 */
static const datetkn datetktbl[] = {
  /* token, type, value */
  {"+infinity", RESERV, DTK_LATE},  /* same as "infinity" */
  {EARLY, RESERV, DTK_EARLY}, /* "-infinity" reserved for "early time" */
  {DA_D, ADBC, AD},     /* "ad" for years > 0 */
  {"allballs", RESERV, DTK_ZULU}, /* 00:00:00 */
  {"am", AMPM, AM},
  {"apr", MONTH, 4},
  {"april", MONTH, 4},
  {"at", IGNORE_DTF, 0},    /* "at" (throwaway) */
  {"aug", MONTH, 8},
  {"august", MONTH, 8},
  {DB_C, ADBC, BC},     /* "bc" for years <= 0 */
  {"d", UNITS, DTK_DAY},    /* "day of month" for ISO input */
  {"dec", MONTH, 12},
  {"december", MONTH, 12},
  {"dow", UNITS, DTK_DOW},  /* day of week */
  {"doy", UNITS, DTK_DOY},  /* day of year */
  {"dst", DTZMOD, SECS_PER_HOUR},
  {EPOCH, RESERV, DTK_EPOCH}, /* "epoch" reserved for system epoch time */
  {"feb", MONTH, 2},
  {"february", MONTH, 2},
  {"fri", DOW, 5},
  {"friday", DOW, 5},
  {"h", UNITS, DTK_HOUR},   /* "hour" */
  {LATE, RESERV, DTK_LATE}, /* "infinity" reserved for "late time" */
  {"isodow", UNITS, DTK_ISODOW},  /* ISO day of week, Sunday == 7 */
  {"isoyear", UNITS, DTK_ISOYEAR},  /* year in terms of the ISO week date */
  {"j", UNITS, DTK_JULIAN},
  {"jan", MONTH, 1},
  {"january", MONTH, 1},
  {"jd", UNITS, DTK_JULIAN},
  {"jul", MONTH, 7},
  {"julian", UNITS, DTK_JULIAN},
  {"july", MONTH, 7},
  {"jun", MONTH, 6},
  {"june", MONTH, 6},
  {"m", UNITS, DTK_MONTH},  /* "month" for ISO input */
  {"mar", MONTH, 3},
  {"march", MONTH, 3},
  {"may", MONTH, 5},
  {"mm", UNITS, DTK_MINUTE},  /* "minute" for ISO input */
  {"mon", DOW, 1},
  {"monday", DOW, 1},
  {"nov", MONTH, 11},
  {"november", MONTH, 11},
  {NOW, RESERV, DTK_NOW},   /* current transaction time */
  {"oct", MONTH, 10},
  {"october", MONTH, 10},
  {"on", IGNORE_DTF, 0},    /* "on" (throwaway) */
  {"pm", AMPM, PM},
  {"s", UNITS, DTK_SECOND}, /* "seconds" for ISO input */
  {"sat", DOW, 6},
  {"saturday", DOW, 6},
  {"sep", MONTH, 9},
  {"sept", MONTH, 9},
  {"september", MONTH, 9},
  {"sun", DOW, 0},
  {"sunday", DOW, 0},
  {"t", ISOTIME, DTK_TIME}, /* Filler for ISO time fields */
  {"thu", DOW, 4},
  {"thur", DOW, 4},
  {"thurs", DOW, 4},
  {"thursday", DOW, 4},
  {TODAY, RESERV, DTK_TODAY}, /* midnight */
  {TOMORROW, RESERV, DTK_TOMORROW}, /* tomorrow midnight */
  {"tue", DOW, 2},
  {"tues", DOW, 2},
  {"tuesday", DOW, 2},
  {"wed", DOW, 3},
  {"wednesday", DOW, 3},
  {"weds", DOW, 3},
  {"y", UNITS, DTK_YEAR},   /* "year" for ISO input */
  {YESTERDAY, RESERV, DTK_YESTERDAY}  /* yesterday midnight */
};

static const int szdatetktbl = sizeof datetktbl / sizeof datetktbl[0];

/*
 * deltatktbl: same format as datetktbl, but holds keywords used to represent
 * time units (eg, for intervals, and for EXTRACT).
 */
static const datetkn deltatktbl[] = {
  /* token, type, value */
  {"@", IGNORE_DTF, 0},   /* postgres relative prefix */
  {DAGO, AGO, 0},       /* "ago" indicates negative time offset */
  {"c", UNITS, DTK_CENTURY},  /* "century" relative */
  {"cent", UNITS, DTK_CENTURY}, /* "century" relative */
  {"centuries", UNITS, DTK_CENTURY},  /* "centuries" relative */
  {DCENTURY, UNITS, DTK_CENTURY}, /* "century" relative */
  {"d", UNITS, DTK_DAY},    /* "day" relative */
  {DDAY, UNITS, DTK_DAY},   /* "day" relative */
  {"days", UNITS, DTK_DAY}, /* "days" relative */
  {"dec", UNITS, DTK_DECADE}, /* "decade" relative */
  {DDECADE, UNITS, DTK_DECADE}, /* "decade" relative */
  {"decades", UNITS, DTK_DECADE}, /* "decades" relative */
  {"decs", UNITS, DTK_DECADE},  /* "decades" relative */
  {"h", UNITS, DTK_HOUR},   /* "hour" relative */
  {DHOUR, UNITS, DTK_HOUR}, /* "hour" relative */
  {"hours", UNITS, DTK_HOUR}, /* "hours" relative */
  {"hr", UNITS, DTK_HOUR},  /* "hour" relative */
  {"hrs", UNITS, DTK_HOUR}, /* "hours" relative */
  {"m", UNITS, DTK_MINUTE}, /* "minute" relative */
  {"microsecon", UNITS, DTK_MICROSEC},  /* "microsecond" relative */
  {"mil", UNITS, DTK_MILLENNIUM}, /* "millennium" relative */
  {"millennia", UNITS, DTK_MILLENNIUM}, /* "millennia" relative */
  {DMILLENNIUM, UNITS, DTK_MILLENNIUM}, /* "millennium" relative */
  {"millisecon", UNITS, DTK_MILLISEC},  /* relative */
  {"mils", UNITS, DTK_MILLENNIUM},  /* "millennia" relative */
  {"min", UNITS, DTK_MINUTE}, /* "minute" relative */
  {"mins", UNITS, DTK_MINUTE},  /* "minutes" relative */
  {DMINUTE, UNITS, DTK_MINUTE}, /* "minute" relative */
  {"minutes", UNITS, DTK_MINUTE}, /* "minutes" relative */
  {"mon", UNITS, DTK_MONTH},  /* "months" relative */
  {"mons", UNITS, DTK_MONTH}, /* "months" relative */
  {DMONTH, UNITS, DTK_MONTH}, /* "month" relative */
  {"months", UNITS, DTK_MONTH},
  {"ms", UNITS, DTK_MILLISEC},
  {"msec", UNITS, DTK_MILLISEC},
  {DMILLISEC, UNITS, DTK_MILLISEC},
  {"mseconds", UNITS, DTK_MILLISEC},
  {"msecs", UNITS, DTK_MILLISEC},
  {"qtr", UNITS, DTK_QUARTER},  /* "quarter" relative */
  {DQUARTER, UNITS, DTK_QUARTER}, /* "quarter" relative */
  {"s", UNITS, DTK_SECOND},
  {"sec", UNITS, DTK_SECOND},
  {DSECOND, UNITS, DTK_SECOND},
  {"seconds", UNITS, DTK_SECOND},
  {"secs", UNITS, DTK_SECOND},
  {DTIMEZONE, UNITS, DTK_TZ}, /* "timezone" time offset */
  {"timezone_h", UNITS, DTK_TZ_HOUR}, /* timezone hour units */
  {"timezone_m", UNITS, DTK_TZ_MINUTE}, /* timezone minutes units */
  {"us", UNITS, DTK_MICROSEC},  /* "microsecond" relative */
  {"usec", UNITS, DTK_MICROSEC},  /* "microsecond" relative */
  {DMICROSEC, UNITS, DTK_MICROSEC}, /* "microsecond" relative */
  {"useconds", UNITS, DTK_MICROSEC},  /* "microseconds" relative */
  {"usecs", UNITS, DTK_MICROSEC}, /* "microseconds" relative */
  {"w", UNITS, DTK_WEEK},   /* "week" relative */
  {DWEEK, UNITS, DTK_WEEK}, /* "week" relative */
  {"weeks", UNITS, DTK_WEEK}, /* "weeks" relative */
  {"y", UNITS, DTK_YEAR},   /* "year" relative */
  {DYEAR, UNITS, DTK_YEAR}, /* "year" relative */
  {"years", UNITS, DTK_YEAR}, /* "years" relative */
  {"yr", UNITS, DTK_YEAR},  /* "year" relative */
  {"yrs", UNITS, DTK_YEAR}  /* "years" relative */
};

static const int szdeltatktbl = sizeof deltatktbl / sizeof deltatktbl[0];

static TimeZoneAbbrevTable *zoneabbrevtbl = NULL;

/* Caches of recent lookup results in the above tables */

static const datetkn *datecache[MAXDATEFIELDS] = {NULL};

static const datetkn *deltacache[MAXDATEFIELDS] = {NULL};

/* Cache for results of timezone abbreviation lookups */

typedef struct TzAbbrevCache
{
  char    abbrev[TOKMAXLEN + 1];  /* always NUL-terminated */
  char    ftype;      /* TZ, DTZ, or DYNTZ */
  int     offset;     /* GMT offset, if fixed-offset */
  pg_tz    *tz;       /* relevant zone, if variable-offset */
} TzAbbrevCache;

static TzAbbrevCache tzabbrevcache[MAXDATEFIELDS];


/*
 * Calendar time to Julian date conversions.
 * Julian date is commonly used in astronomical applications,
 *  since it is numerically accurate and computationally simple.
 * The algorithms here will accurately convert between Julian day
 *  and calendar date for all non-negative Julian days
 *  (i.e. from Nov 24, -4713 on).
 *
 * Rewritten to eliminate overflow problems. This now allows the
 * routines to work correctly for all Julian day counts from
 * 0 to 2147483647  (Nov 24, -4713 to Jun 3, 5874898) assuming
 * a 32-bit integer. Longer types should also work to the limits
 * of their precision.
 *
 * Actually, date2j() will work sanely, in the sense of producing
 * valid negative Julian dates, significantly before Nov 24, -4713.
 * We rely on it to do so back to Nov 1, -4713; see IS_VALID_JULIAN()
 * and associated commentary in timestamp.h.
 */

int
date2j(int year, int month, int day)
{
  int     julian;
  int     century;

  if (month > 2)
  {
    month += 1;
    year += 4800;
  }
  else
  {
    month += 13;
    year += 4799;
  }

  century = year / 100;
  julian = year * 365 - 32167;
  julian += year / 4 - century + century / 4;
  julian += 7834 * month / 256 + day;

  return julian;
}                /* date2j() */

void
j2date(int jd, int *year, int *month, int *day)
{
  unsigned int julian;
  unsigned int quad;
  unsigned int extra;
  int     y;

  julian = jd;
  julian += 32044;
  quad = julian / 146097;
  extra = (julian - quad * 146097) * 4 + 3;
  julian += 60 + quad * 3 + extra / 146097;
  quad = julian / 1461;
  julian -= quad * 1461;
  y = julian * 4 / 1461;
  julian = ((y != 0) ? ((julian + 305) % 365) : ((julian + 306) % 366))
    + 123;
  y += quad * 4;
  *year = y - 4800;
  quad = julian * 2141 / 65536;
  *day = julian - 7834 * quad / 256;
  *month = (quad + 10) % MONTHS_PER_YEAR + 1;
}                /* j2date() */


/*
 * j2day - convert Julian date to day-of-week (0..6 == Sun..Sat)
 *
 * Note: various places use the locution j2day(date - 1) to produce a
 * result according to the convention 0..6 = Mon..Sun.  This is a bit of
 * a crock, but will work as long as the computation here is just a modulo.
 */
int
j2day(int date)
{
  date += 1;
  date %= 7;
  /* Cope if division truncates towards zero, as it probably does */
  if (date < 0)
    date += 7;

  return date;
}                /* j2day() */


/*
 * GetCurrentDateTime()
 *
 * Get the transaction start time ("now()") broken down as a struct pg_tm,
 * converted according to the session timezone setting.
 *
 * This is just a convenience wrapper for GetCurrentTimeUsec, to cover the
 * case where caller doesn't need either fractional seconds or tz offset.
 */
void
GetCurrentDateTime(struct pg_tm *tm)
{
  fsec_t    fsec;

  GetCurrentTimeUsec(tm, &fsec, NULL);
}

/*
 * GetCurrentTimeUsec()
 *
 * Get the transaction start time ("now()") broken down as a struct pg_tm,
 * including fractional seconds and timezone offset.  The time is converted
 * according to the session timezone setting.
 *
 * Callers may pass tzp = NULL if they don't need the offset, but this does
 * not affect the conversion behavior (unlike timestamp2tm()).
 *
 * Internally, we cache the result, since this could be called many times
 * in a transaction, within which now() doesn't change.
 */
void
GetCurrentTimeUsec(struct pg_tm *tm, fsec_t *fsec, int *tzp)
{
  TimestampTz cur_ts = GetCurrentTransactionStartTimestamp();

  /*
   * The cache key must include both current time and current timezone.  By
   * representing the timezone by just a pointer, we're assuming that
   * distinct timezone settings could never have the same pointer value.
   * This is true by virtue of the hashtable used inside pg_tzset();
   * however, it might need another look if we ever allow entries in that
   * hash to be recycled.
   */
  static TimestampTz cache_ts = 0;
  static pg_tz *cache_timezone = NULL;
  static struct pg_tm cache_tm;
  static fsec_t cache_fsec;
  static int  cache_tz;

  if (cur_ts != cache_ts || session_timezone != cache_timezone)
  {
    /*
     * Make sure cache is marked invalid in case of error after partial
     * update within timestamp2tm.
     */
    cache_timezone = NULL;

    /*
     * Perform the computation, storing results into cache.  We do not
     * really expect any error here, since current time surely ought to be
     * within range, but check just for sanity's sake.
     */
    if (timestamp2tm(cur_ts, &cache_tz, &cache_tm, &cache_fsec,
             NULL, session_timezone) != 0)
      ereport(ERROR,
          (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
           errmsg("timestamp out of range")));

    /* OK, so mark the cache valid. */
    cache_ts = cur_ts;
    cache_timezone = session_timezone;
  }

  *tm = cache_tm;
  *fsec = cache_fsec;
  if (tzp != NULL)
    *tzp = cache_tz;
}


/*
 * Append seconds and fractional seconds (if any) at *cp.
 *
 * precision is the max number of fraction digits, fillzeros says to
 * pad to two integral-seconds digits.
 *
 * Returns a pointer to the new end of string.  No NUL terminator is put
 * there; callers are responsible for NUL terminating str themselves.
 *
 * Note that any sign is stripped from the input sec and fsec values.
 */
static char *
AppendSeconds(char *cp, int sec, fsec_t fsec, int precision, bool fillzeros)
{
  Assert(precision >= 0);

  if (fillzeros)
    cp = pg_ultostr_zeropad(cp, abs(sec), 2);
  else
    cp = pg_ultostr(cp, abs(sec));

  /* fsec_t is just an int32 */
  if (fsec != 0)
  {
    int32   value = abs(fsec);
    char     *end = &cp[precision + 1];
    bool    gotnonzero = false;

    *cp++ = '.';

    /*
     * Append the fractional seconds part.  Note that we don't want any
     * trailing zeros here, so since we're building the number in reverse
     * we'll skip appending zeros until we've output a non-zero digit.
     */
    while (precision--)
    {
      int32   oldval = value;
      int32   remainder;

      value /= 10;
      remainder = oldval - value * 10;

      /* check if we got a non-zero */
      if (remainder)
        gotnonzero = true;

      if (gotnonzero)
        cp[precision] = '0' + remainder;
      else
        end = &cp[precision];
    }

    /*
     * If we still have a non-zero value then precision must have not been
     * enough to print the number.  We punt the problem to pg_ultostr(),
     * which will generate a correct answer in the minimum valid width.
     */
    if (value)
      return pg_ultostr(cp, abs(fsec));

    return end;
  }
  else
    return cp;
}


/*
 * Variant of above that's specialized to timestamp case.
 *
 * Returns a pointer to the new end of string.  No NUL terminator is put
 * there; callers are responsible for NUL terminating str themselves.
 */
static char *
AppendTimestampSeconds(char *cp, struct pg_tm *tm, fsec_t fsec)
{
  return AppendSeconds(cp, tm->tm_sec, fsec, MAX_TIMESTAMP_PRECISION, true);
}


/*
 * Add val * multiplier to *sum.
 * Returns true if successful, false on overflow.
 */
static bool
int64_multiply_add(int64 val, int64 multiplier, int64 *sum)
{
  int64   product;

  if (pg_mul_s64_overflow(val, multiplier, &product) ||
    pg_add_s64_overflow(*sum, product, sum))
    return false;
  return true;
}

/*
 * Multiply frac by scale (to produce microseconds) and add to itm_in->tm_usec.
 * Returns true if successful, false if itm_in overflows.
 */
static bool
AdjustFractMicroseconds(double frac, int64 scale,
            struct pg_itm_in *itm_in)
{
  int64   usec;

  /* Fast path for common case */
  if (frac == 0)
    return true;

  /*
   * We assume the input frac has abs value less than 1, so overflow of frac
   * or usec is not an issue for interesting values of scale.
   */
  frac *= scale;
  usec = (int64) frac;

  /* Round off any fractional microsecond */
  frac -= usec;
  if (frac > 0.5)
    usec++;
  else if (frac < -0.5)
    usec--;

  return !pg_add_s64_overflow(itm_in->tm_usec, usec, &itm_in->tm_usec);
}

/*
 * Multiply frac by scale (to produce days).  Add the integral part of the
 * result to itm_in->tm_mday, the fractional part to itm_in->tm_usec.
 * Returns true if successful, false if itm_in overflows.
 */
static bool
AdjustFractDays(double frac, int scale,
        struct pg_itm_in *itm_in)
{
  int     extra_days;

  /* Fast path for common case */
  if (frac == 0)
    return true;

  /*
   * We assume the input frac has abs value less than 1, so overflow of frac
   * or extra_days is not an issue.
   */
  frac *= scale;
  extra_days = (int) frac;

  /* ... but this could overflow, if tm_mday is already nonzero */
  if (pg_add_s32_overflow(itm_in->tm_mday, extra_days, &itm_in->tm_mday))
    return false;

  /* Handle any fractional day */
  frac -= extra_days;
  return AdjustFractMicroseconds(frac, USECS_PER_DAY, itm_in);
}

/*
 * Multiply frac by scale (to produce years), then further scale up to months.
 * Add the integral part of the result to itm_in->tm_mon, discarding any
 * fractional part.
 * Returns true if successful, false if itm_in overflows.
 */
static bool
AdjustFractYears(double frac, int scale,
         struct pg_itm_in *itm_in)
{
  /*
   * As above, we assume abs(frac) < 1, so this can't overflow for any
   * interesting value of scale.
   */
  int     extra_months = (int) rint(frac * scale * MONTHS_PER_YEAR);

  return !pg_add_s32_overflow(itm_in->tm_mon, extra_months, &itm_in->tm_mon);
}

/*
 * Add (val + fval) * scale to itm_in->tm_usec.
 * Returns true if successful, false if itm_in overflows.
 */
static bool
AdjustMicroseconds(int64 val, double fval, int64 scale,
           struct pg_itm_in *itm_in)
{
  /* Handle the integer part */
  if (!int64_multiply_add(val, scale, &itm_in->tm_usec))
    return false;
  /* Handle the float part */
  return AdjustFractMicroseconds(fval, scale, itm_in);
}

/*
 * Multiply val by scale (to produce days) and add to itm_in->tm_mday.
 * Returns true if successful, false if itm_in overflows.
 */
static bool
AdjustDays(int64 val, int scale, struct pg_itm_in *itm_in)
{
  int     days;

  if (val < INT_MIN || val > INT_MAX)
    return false;
  return !pg_mul_s32_overflow((int32) val, scale, &days) &&
    !pg_add_s32_overflow(itm_in->tm_mday, days, &itm_in->tm_mday);
}

/*
 * Add val to itm_in->tm_mon (no need for scale here, as val is always
 * in months already).
 * Returns true if successful, false if itm_in overflows.
 */
static bool
AdjustMonths(int64 val, struct pg_itm_in *itm_in)
{
  if (val < INT_MIN || val > INT_MAX)
    return false;
  return !pg_add_s32_overflow(itm_in->tm_mon, (int32) val, &itm_in->tm_mon);
}

/*
 * Multiply val by scale (to produce years) and add to itm_in->tm_year.
 * Returns true if successful, false if itm_in overflows.
 */
static bool
AdjustYears(int64 val, int scale,
      struct pg_itm_in *itm_in)
{
  int     years;

  if (val < INT_MIN || val > INT_MAX)
    return false;
  return !pg_mul_s32_overflow((int32) val, scale, &years) &&
    !pg_add_s32_overflow(itm_in->tm_year, years, &itm_in->tm_year);
}


/*
 * Parse the fractional part of a number (decimal point and optional digits,
 * followed by end of string).  Returns the fractional value into *frac.
 *
 * Returns 0 if successful, DTERR code if bogus input detected.
 */
static int
ParseFraction(char *cp, double *frac)
{
  /* Caller should always pass the start of the fraction part */
  Assert(*cp == '.');

  /*
   * We want to allow just "." with no digits, but some versions of strtod
   * will report EINVAL for that, so special-case it.
   */
  if (cp[1] == '\0')
  {
    *frac = 0;
  }
  else
  {
    /*
     * On the other hand, let's reject anything that's not digits after
     * the ".".  strtod is happy with input like ".123e9", but that'd
     * break callers' expectation that the result is in 0..1.  (It's quite
     * difficult to get here with such input, but not impossible.)
     */
    if (strspn(cp + 1, "0123456789") != strlen(cp + 1))
      return DTERR_BAD_FORMAT;

    errno = 0;
    *frac = strtod(cp, &cp);
    /* check for parse failure (probably redundant given prior check) */
    if (*cp != '\0' || errno != 0)
      return DTERR_BAD_FORMAT;
  }
  return 0;
}

/*
 * Fetch a fractional-second value with suitable error checking.
 * Same as ParseFraction except we convert the result to integer microseconds.
 */
static int
ParseFractionalSecond(char *cp, fsec_t *fsec)
{
  double    frac;
  int     dterr;

  dterr = ParseFraction(cp, &frac);
  if (dterr)
    return dterr;
  *fsec = rint(frac * 1000000);
  return 0;
}


/* ParseDateTime()
 *  Break string into tokens based on a date/time context.
 *  Returns 0 if successful, DTERR code if bogus input detected.
 *
 * timestr - the input string
 * workbuf - workspace for field string storage. This must be
 *   larger than the largest legal input for this datetime type --
 *   some additional space will be needed to NUL terminate fields.
 * buflen - the size of workbuf
 * field[] - pointers to field strings are returned in this array
 * ftype[] - field type indicators are returned in this array
 * maxfields - dimensions of the above two arrays
 * *numfields - set to the actual number of fields detected
 *
 * The fields extracted from the input are stored as separate,
 * null-terminated strings in the workspace at workbuf. Any text is
 * converted to lower case.
 *
 * Several field types are assigned:
 *  DTK_NUMBER - digits and (possibly) a decimal point
 *  DTK_DATE - digits and two delimiters, or digits and text
 *  DTK_TIME - digits, colon delimiters, and possibly a decimal point
 *  DTK_STRING - text (no digits or punctuation)
 *  DTK_SPECIAL - leading "+" or "-" followed by text
 *  DTK_TZ - leading "+" or "-" followed by digits (also eats ':', '.', '-')
 *
 * Note that some field types can hold unexpected items:
 *  DTK_NUMBER can hold date fields (yy.ddd)
 *  DTK_STRING can hold months (January) and time zones (PST)
 *  DTK_DATE can hold time zone names (America/New_York, GMT-8)
 */
int
ParseDateTime(const char *timestr, char *workbuf, size_t buflen,
        char **field, int *ftype, int maxfields, int *numfields)
{
  int     nf = 0;
  const char *cp = timestr;
  char     *bufp = workbuf;
  const char *bufend = workbuf + buflen;

  /*
   * Set the character pointed-to by "bufptr" to "newchar", and increment
   * "bufptr". "end" gives the end of the buffer -- we return an error if
   * there is no space left to append a character to the buffer. Note that
   * "bufptr" is evaluated twice.
   */
#define APPEND_CHAR(bufptr, end, newchar)   \
  do                      \
  {                     \
    if (((bufptr) + 1) >= (end))     \
      return DTERR_BAD_FORMAT;     \
    *(bufptr)++ = newchar;          \
  } while (0)

  /* outer loop through fields */
  while (*cp != '\0')
  {
    /* Ignore spaces between fields */
    if (isspace((unsigned char) *cp))
    {
      cp++;
      continue;
    }

    /* Record start of current field */
    if (nf >= maxfields)
      return DTERR_BAD_FORMAT;
    field[nf] = bufp;

    /* leading digit? then date or time */
    if (isdigit((unsigned char) *cp))
    {
      APPEND_CHAR(bufp, bufend, *cp++);
      while (isdigit((unsigned char) *cp))
        APPEND_CHAR(bufp, bufend, *cp++);

      /* time field? */
      if (*cp == ':')
      {
        ftype[nf] = DTK_TIME;
        APPEND_CHAR(bufp, bufend, *cp++);
        while (isdigit((unsigned char) *cp) ||
             (*cp == ':') || (*cp == '.'))
          APPEND_CHAR(bufp, bufend, *cp++);
      }
      /* date field? allow embedded text month */
      else if (*cp == '-' || *cp == '/' || *cp == '.')
      {
        /* save delimiting character to use later */
        char    delim = *cp;

        APPEND_CHAR(bufp, bufend, *cp++);
        /* second field is all digits? then no embedded text month */
        if (isdigit((unsigned char) *cp))
        {
          ftype[nf] = ((delim == '.') ? DTK_NUMBER : DTK_DATE);
          while (isdigit((unsigned char) *cp))
            APPEND_CHAR(bufp, bufend, *cp++);

          /*
           * insist that the delimiters match to get a three-field
           * date.
           */
          if (*cp == delim)
          {
            ftype[nf] = DTK_DATE;
            APPEND_CHAR(bufp, bufend, *cp++);
            while (isdigit((unsigned char) *cp) || *cp == delim)
              APPEND_CHAR(bufp, bufend, *cp++);
          }
        }
        else
        {
          ftype[nf] = DTK_DATE;
          while (isalnum((unsigned char) *cp) || *cp == delim)
            APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
        }
      }

      /*
       * otherwise, number only and will determine year, month, day, or
       * concatenated fields later...
       */
      else
        ftype[nf] = DTK_NUMBER;
    }
    /* Leading decimal point? Then fractional seconds... */
    else if (*cp == '.')
    {
      APPEND_CHAR(bufp, bufend, *cp++);
      while (isdigit((unsigned char) *cp))
        APPEND_CHAR(bufp, bufend, *cp++);

      ftype[nf] = DTK_NUMBER;
    }

    /*
     * text? then date string, month, day of week, special, or timezone
     */
    else if (isalpha((unsigned char) *cp))
    {
      bool    is_date;

      ftype[nf] = DTK_STRING;
      APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
      while (isalpha((unsigned char) *cp))
        APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));

      /*
       * Dates can have embedded '-', '/', or '.' separators.  It could
       * also be a timezone name containing embedded '/', '+', '-', '_',
       * or ':' (but '_' or ':' can't be the first punctuation). If the
       * next character is a digit or '+', we need to check whether what
       * we have so far is a recognized non-timezone keyword --- if so,
       * don't believe that this is the start of a timezone.
       */
      is_date = false;
      if (*cp == '-' || *cp == '/' || *cp == '.')
        is_date = true;
      else if (*cp == '+' || isdigit((unsigned char) *cp))
      {
        *bufp = '\0'; /* null-terminate current field value */
        /* we need search only the core token table, not TZ names */
        if (datebsearch(field[nf], datetktbl, szdatetktbl) == NULL)
          is_date = true;
      }
      if (is_date)
      {
        ftype[nf] = DTK_DATE;
        do
        {
          APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
        } while (*cp == '+' || *cp == '-' ||
             *cp == '/' || *cp == '_' ||
             *cp == '.' || *cp == ':' ||
             isalnum((unsigned char) *cp));
      }
    }
    /* sign? then special or numeric timezone */
    else if (*cp == '+' || *cp == '-')
    {
      APPEND_CHAR(bufp, bufend, *cp++);
      /* soak up leading whitespace */
      while (isspace((unsigned char) *cp))
        cp++;
      /* numeric timezone? */
      /* note that "DTK_TZ" could also be a signed float or yyyy-mm */
      if (isdigit((unsigned char) *cp))
      {
        ftype[nf] = DTK_TZ;
        APPEND_CHAR(bufp, bufend, *cp++);
        while (isdigit((unsigned char) *cp) ||
             *cp == ':' || *cp == '.' || *cp == '-')
          APPEND_CHAR(bufp, bufend, *cp++);
      }
      /* special? */
      else if (isalpha((unsigned char) *cp))
      {
        ftype[nf] = DTK_SPECIAL;
        APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
        while (isalpha((unsigned char) *cp))
          APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
      }
      /* otherwise something wrong... */
      else
        return DTERR_BAD_FORMAT;
    }
    /* ignore other punctuation but use as delimiter */
    else if (ispunct((unsigned char) *cp))
    {
      cp++;
      continue;
    }
    /* otherwise, something is not right... */
    else
      return DTERR_BAD_FORMAT;

    /* force in a delimiter after each field */
    *bufp++ = '\0';
    nf++;
  }

  *numfields = nf;

  return 0;
}


/* DecodeDateTime()
 * Interpret previously parsed fields for general date and time.
 * Return 0 if full date, 1 if only time, and negative DTERR code if problems.
 * (Currently, all callers treat 1 as an error return too.)
 *
 * Inputs are field[] and ftype[] arrays, of length nf.
 * Other arguments are outputs.
 *
 *    External format(s):
 *        "<weekday> <month>-<day>-<year> <hour>:<minute>:<second>"
 *        "Fri Feb-7-1997 15:23:27"
 *        "Feb-7-1997 15:23:27"
 *        "2-7-1997 15:23:27"
 *        "1997-2-7 15:23:27"
 *        "1997.038 15:23:27"   (day of year 1-366)
 *    Also supports input in compact time:
 *        "970207 152327"
 *        "97038 152327"
 *        "20011225T040506.789-07"
 *
 * Use the system-provided functions to get the current time zone
 * if not specified in the input string.
 *
 * If the date is outside the range of pg_time_t (in practice that could only
 * happen if pg_time_t is just 32 bits), then assume UTC time zone - thomas
 * 1997-05-27
 */
int
DecodeDateTime(char **field, int *ftype, int nf,
         int *dtype, struct pg_tm *tm, fsec_t *fsec, int *tzp,
         DateTimeErrorExtra *extra)
{
  int     fmask = 0,
        tmask,
        type;
  int     ptype = 0;    /* "prefix type" for ISO and Julian formats */
  int     i;
  int     val;
  int     dterr;
  int     mer = HR24;
  bool    haveTextMonth = false;
  bool    isjulian = false;
  bool    is2digits = false;
  bool    bc = false;
  pg_tz    *namedTz = NULL;
  pg_tz    *abbrevTz = NULL;
  pg_tz    *valtz;
  char     *abbrev = NULL;
  struct pg_tm cur_tm;

  /*
   * We'll insist on at least all of the date fields, but initialize the
   * remaining fields in case they are not set later...
   */
  *dtype = DTK_DATE;
  tm->tm_hour = 0;
  tm->tm_min = 0;
  tm->tm_sec = 0;
  *fsec = 0;
  /* don't know daylight savings time status apriori */
  tm->tm_isdst = -1;
  if (tzp != NULL)
    *tzp = 0;

  for (i = 0; i < nf; i++)
  {
    switch (ftype[i])
    {
      case DTK_DATE:

        /*
         * Integral julian day with attached time zone? All other
         * forms with JD will be separated into distinct fields, so we
         * handle just this case here.
         */
        if (ptype == DTK_JULIAN)
        {
          char     *cp;
          int     jday;

          if (tzp == NULL)
            return DTERR_BAD_FORMAT;

          errno = 0;
          jday = strtoint(field[i], &cp, 10);
          if (errno == ERANGE || jday < 0)
            return DTERR_FIELD_OVERFLOW;

          j2date(jday, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
          isjulian = true;

          /* Get the time zone from the end of the string */
          dterr = DecodeTimezone(cp, tzp);
          if (dterr)
            return dterr;

          tmask = DTK_DATE_M | DTK_TIME_M | DTK_M(TZ);
          ptype = 0;
          break;
        }

        /*
         * Already have a date? Then this might be a time zone name
         * with embedded punctuation (e.g. "America/New_York") or a
         * run-together time with trailing time zone (e.g. hhmmss-zz).
         * - thomas 2001-12-25
         *
         * We consider it a time zone if we already have month & day.
         * This is to allow the form "mmm dd hhmmss tz year", which
         * we've historically accepted.
         */
        else if (ptype != 0 ||
             ((fmask & (DTK_M(MONTH) | DTK_M(DAY))) ==
              (DTK_M(MONTH) | DTK_M(DAY))))
        {
          /* No time zone accepted? Then quit... */
          if (tzp == NULL)
            return DTERR_BAD_FORMAT;

          if (isdigit((unsigned char) *field[i]) || ptype != 0)
          {
            char     *cp;

            /*
             * Allow a preceding "t" field, but no other units.
             */
            if (ptype != 0)
            {
              /* Sanity check; should not fail this test */
              if (ptype != DTK_TIME)
                return DTERR_BAD_FORMAT;
              ptype = 0;
            }

            /*
             * Starts with a digit but we already have a time
             * field? Then we are in trouble with a date and time
             * already...
             */
            if ((fmask & DTK_TIME_M) == DTK_TIME_M)
              return DTERR_BAD_FORMAT;

            if ((cp = strchr(field[i], '-')) == NULL)
              return DTERR_BAD_FORMAT;

            /* Get the time zone from the end of the string */
            dterr = DecodeTimezone(cp, tzp);
            if (dterr)
              return dterr;
            *cp = '\0';

            /*
             * Then read the rest of the field as a concatenated
             * time
             */
            dterr = DecodeNumberField(strlen(field[i]), field[i],
                          fmask,
                          &tmask, tm,
                          fsec, &is2digits);
            if (dterr < 0)
              return dterr;

            /*
             * modify tmask after returning from
             * DecodeNumberField()
             */
            tmask |= DTK_M(TZ);
          }
          else
          {
            namedTz = pg_tzset(field[i]);
            if (!namedTz)
            {
              extra->dtee_timezone = field[i];
              return DTERR_BAD_TIMEZONE;
            }
            /* we'll apply the zone setting below */
            tmask = DTK_M(TZ);
          }
        }
        else
        {
          dterr = DecodeDate(field[i], fmask,
                     &tmask, &is2digits, tm);
          if (dterr)
            return dterr;
        }
        break;

      case DTK_TIME:

        /*
         * This might be an ISO time following a "t" field.
         */
        if (ptype != 0)
        {
          /* Sanity check; should not fail this test */
          if (ptype != DTK_TIME)
            return DTERR_BAD_FORMAT;
          ptype = 0;
        }
        dterr = DecodeTime(field[i], fmask, INTERVAL_FULL_RANGE,
                   &tmask, tm, fsec);
        if (dterr)
          return dterr;

        /* check for time overflow */
        if (time_overflows(tm->tm_hour, tm->tm_min, tm->tm_sec,
                   *fsec))
          return DTERR_FIELD_OVERFLOW;
        break;

      case DTK_TZ:
        {
          int     tz;

          if (tzp == NULL)
            return DTERR_BAD_FORMAT;

          dterr = DecodeTimezone(field[i], &tz);
          if (dterr)
            return dterr;
          *tzp = tz;
          tmask = DTK_M(TZ);
        }
        break;

      case DTK_NUMBER:

        /*
         * Deal with cases where previous field labeled this one
         */
        if (ptype != 0)
        {
          char     *cp;
          int     value;

          errno = 0;
          value = strtoint(field[i], &cp, 10);
          if (errno == ERANGE)
            return DTERR_FIELD_OVERFLOW;
          if (*cp != '.' && *cp != '\0')
            return DTERR_BAD_FORMAT;

          switch (ptype)
          {
            case DTK_JULIAN:
              /* previous field was a label for "julian date" */
              if (value < 0)
                return DTERR_FIELD_OVERFLOW;
              tmask = DTK_DATE_M;
              j2date(value, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
              isjulian = true;

              /* fractional Julian Day? */
              if (*cp == '.')
              {
                double    time;

                dterr = ParseFraction(cp, &time);
                if (dterr)
                  return dterr;
                time *= USECS_PER_DAY;
                dt2time(time,
                    &tm->tm_hour, &tm->tm_min,
                    &tm->tm_sec, fsec);
                tmask |= DTK_TIME_M;
              }
              break;

            case DTK_TIME:
              /* previous field was "t" for ISO time */
              dterr = DecodeNumberField(strlen(field[i]), field[i],
                            (fmask | DTK_DATE_M),
                            &tmask, tm,
                            fsec, &is2digits);
              if (dterr < 0)
                return dterr;
              if (tmask != DTK_TIME_M)
                return DTERR_BAD_FORMAT;
              break;

            default:
              return DTERR_BAD_FORMAT;
              break;
          }

          ptype = 0;
          *dtype = DTK_DATE;
        }
        else
        {
          char     *cp;
          int     flen;

          flen = strlen(field[i]);
          cp = strchr(field[i], '.');

          /* Embedded decimal and no date yet? */
          if (cp != NULL && !(fmask & DTK_DATE_M))
          {
            dterr = DecodeDate(field[i], fmask,
                       &tmask, &is2digits, tm);
            if (dterr)
              return dterr;
          }
          /* embedded decimal and several digits before? */
          else if (cp != NULL && flen - strlen(cp) > 2)
          {
            /*
             * Interpret as a concatenated date or time Set the
             * type field to allow decoding other fields later.
             * Example: 20011223 or 040506
             */
            dterr = DecodeNumberField(flen, field[i], fmask,
                          &tmask, tm,
                          fsec, &is2digits);
            if (dterr < 0)
              return dterr;
          }

          /*
           * Is this a YMD or HMS specification, or a year number?
           * YMD and HMS are required to be six digits or more, so
           * if it is 5 digits, it is a year.  If it is six or more
           * digits, we assume it is YMD or HMS unless no date and
           * no time values have been specified.  This forces 6+
           * digit years to be at the end of the string, or to use
           * the ISO date specification.
           */
          else if (flen >= 6 && (!(fmask & DTK_DATE_M) ||
                       !(fmask & DTK_TIME_M)))
          {
            dterr = DecodeNumberField(flen, field[i], fmask,
                          &tmask, tm,
                          fsec, &is2digits);
            if (dterr < 0)
              return dterr;
          }
          /* otherwise it is a single date/time field... */
          else
          {
            dterr = DecodeNumber(flen, field[i],
                       haveTextMonth, fmask,
                       &tmask, tm,
                       fsec, &is2digits);
            if (dterr)
              return dterr;
          }
        }
        break;

      case DTK_STRING:
      case DTK_SPECIAL:
        /* timezone abbrevs take precedence over built-in tokens */
        dterr = DecodeTimezoneAbbrev(i, field[i],
                       &type, &val, &valtz, extra);
        if (dterr)
          return dterr;
        if (type == UNKNOWN_FIELD)
          type = DecodeSpecial(i, field[i], &val);
        if (type == IGNORE_DTF)
          continue;

        tmask = DTK_M(type);
        switch (type)
        {
          case RESERV:
            switch (val)
            {
              case DTK_NOW:
                tmask = (DTK_DATE_M | DTK_TIME_M | DTK_M(TZ));
                *dtype = DTK_DATE;
                GetCurrentTimeUsec(tm, fsec, tzp);
                break;

              case DTK_YESTERDAY:
                tmask = DTK_DATE_M;
                *dtype = DTK_DATE;
                GetCurrentDateTime(&cur_tm);
                j2date(date2j(cur_tm.tm_year, cur_tm.tm_mon, cur_tm.tm_mday) - 1,
                     &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
                break;

              case DTK_TODAY:
                tmask = DTK_DATE_M;
                *dtype = DTK_DATE;
                GetCurrentDateTime(&cur_tm);
                tm->tm_year = cur_tm.tm_year;
                tm->tm_mon = cur_tm.tm_mon;
                tm->tm_mday = cur_tm.tm_mday;
                break;

              case DTK_TOMORROW:
                tmask = DTK_DATE_M;
                *dtype = DTK_DATE;
                GetCurrentDateTime(&cur_tm);
                j2date(date2j(cur_tm.tm_year, cur_tm.tm_mon, cur_tm.tm_mday) + 1,
                     &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
                break;

              case DTK_ZULU:
                tmask = (DTK_TIME_M | DTK_M(TZ));
                *dtype = DTK_DATE;
                tm->tm_hour = 0;
                tm->tm_min = 0;
                tm->tm_sec = 0;
                if (tzp != NULL)
                  *tzp = 0;
                break;

              case DTK_EPOCH:
              case DTK_LATE:
              case DTK_EARLY:
                tmask = (DTK_DATE_M | DTK_TIME_M | DTK_M(TZ));
                *dtype = val;
                /* caller ignores tm for these dtype codes */
                break;

              default:
                elog(ERROR, "unrecognized RESERV datetime token: %d",
                   val);
            }

            break;

          case MONTH:

            /*
             * already have a (numeric) month? then see if we can
             * substitute...
             */
            if ((fmask & DTK_M(MONTH)) && !haveTextMonth &&
              !(fmask & DTK_M(DAY)) && tm->tm_mon >= 1 &&
              tm->tm_mon <= 31)
            {
              tm->tm_mday = tm->tm_mon;
              tmask = DTK_M(DAY);
            }
            haveTextMonth = true;
            tm->tm_mon = val;
            break;

          case DTZMOD:

            /*
             * daylight savings time modifier (solves "MET DST"
             * syntax)
             */
            tmask |= DTK_M(DTZ);
            tm->tm_isdst = 1;
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            *tzp -= val;
            break;

          case DTZ:

            /*
             * set mask for TZ here _or_ check for DTZ later when
             * getting default timezone
             */
            tmask |= DTK_M(TZ);
            tm->tm_isdst = 1;
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            *tzp = -val;
            break;

          case TZ:
            tm->tm_isdst = 0;
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            *tzp = -val;
            break;

          case DYNTZ:
            tmask |= DTK_M(TZ);
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            /* we'll determine the actual offset later */
            abbrevTz = valtz;
            abbrev = field[i];
            break;

          case AMPM:
            mer = val;
            break;

          case ADBC:
            bc = (val == BC);
            break;

          case DOW:
            tm->tm_wday = val;
            break;

          case UNITS:
            tmask = 0;
            /* reject consecutive unhandled units */
            if (ptype != 0)
              return DTERR_BAD_FORMAT;
            ptype = val;
            break;

          case ISOTIME:

            /*
             * This is a filler field "t" indicating that the next
             * field is time. Try to verify that this is sensible.
             */
            tmask = 0;

            /* No preceding date? Then quit... */
            if ((fmask & DTK_DATE_M) != DTK_DATE_M)
              return DTERR_BAD_FORMAT;

            /* reject consecutive unhandled units */
            if (ptype != 0)
              return DTERR_BAD_FORMAT;
            ptype = val;
            break;

          case UNKNOWN_FIELD:

            /*
             * Before giving up and declaring error, check to see
             * if it is an all-alpha timezone name.
             */
            namedTz = pg_tzset(field[i]);
            if (!namedTz)
              return DTERR_BAD_FORMAT;
            /* we'll apply the zone setting below */
            tmask = DTK_M(TZ);
            break;

          default:
            return DTERR_BAD_FORMAT;
        }
        break;

      default:
        return DTERR_BAD_FORMAT;
    }

    if (tmask & fmask)
      return DTERR_BAD_FORMAT;
    fmask |= tmask;
  }              /* end loop over fields */

  /* reject if prefix type appeared and was never handled */
  if (ptype != 0)
    return DTERR_BAD_FORMAT;

  /* do additional checking for normal date specs (but not "infinity" etc) */
  if (*dtype == DTK_DATE)
  {
    /* do final checking/adjustment of Y/M/D fields */
    dterr = ValidateDate(fmask, isjulian, is2digits, bc, tm);
    if (dterr)
      return dterr;

    /* handle AM/PM */
    if (mer != HR24 && tm->tm_hour > HOURS_PER_DAY / 2)
      return DTERR_FIELD_OVERFLOW;
    if (mer == AM && tm->tm_hour == HOURS_PER_DAY / 2)
      tm->tm_hour = 0;
    else if (mer == PM && tm->tm_hour != HOURS_PER_DAY / 2)
      tm->tm_hour += HOURS_PER_DAY / 2;

    /* check for incomplete input */
    if ((fmask & DTK_DATE_M) != DTK_DATE_M)
    {
      if ((fmask & DTK_TIME_M) == DTK_TIME_M)
        return 1;
      return DTERR_BAD_FORMAT;
    }

    /*
     * If we had a full timezone spec, compute the offset (we could not do
     * it before, because we need the date to resolve DST status).
     */
    if (namedTz != NULL)
    {
      /* daylight savings time modifier disallowed with full TZ */
      if (fmask & DTK_M(DTZMOD))
        return DTERR_BAD_FORMAT;

      *tzp = DetermineTimeZoneOffset(tm, namedTz);
    }

    /*
     * Likewise, if we had a dynamic timezone abbreviation, resolve it
     * now.
     */
    if (abbrevTz != NULL)
    {
      /* daylight savings time modifier disallowed with dynamic TZ */
      if (fmask & DTK_M(DTZMOD))
        return DTERR_BAD_FORMAT;

      *tzp = DetermineTimeZoneAbbrevOffset(tm, abbrev, abbrevTz);
    }

    /* timezone not specified? then use session timezone */
    if (tzp != NULL && !(fmask & DTK_M(TZ)))
    {
      /*
       * daylight savings time modifier but no standard timezone? then
       * error
       */
      if (fmask & DTK_M(DTZMOD))
        return DTERR_BAD_FORMAT;

      *tzp = DetermineTimeZoneOffset(tm, session_timezone);
    }
  }

  return 0;
}


/* DetermineTimeZoneOffset()
 *
 * Given a struct pg_tm in which tm_year, tm_mon, tm_mday, tm_hour, tm_min,
 * and tm_sec fields are set, and a zic-style time zone definition, determine
 * the applicable GMT offset and daylight-savings status at that time.
 * Set the struct pg_tm's tm_isdst field accordingly, and return the GMT
 * offset as the function result.
 *
 * Note: if the date is out of the range we can deal with, we return zero
 * as the GMT offset and set tm_isdst = 0.  We don't throw an error here,
 * though probably some higher-level code will.
 */
int
DetermineTimeZoneOffset(struct pg_tm *tm, pg_tz *tzp)
{
  pg_time_t t;

  return DetermineTimeZoneOffsetInternal(tm, tzp, &t);
}


/* DetermineTimeZoneOffsetInternal()
 *
 * As above, but also return the actual UTC time imputed to the date/time
 * into *tp.
 *
 * In event of an out-of-range date, we punt by returning zero into *tp.
 * This is okay for the immediate callers but is a good reason for not
 * exposing this worker function globally.
 *
 * Note: it might seem that we should use mktime() for this, but bitter
 * experience teaches otherwise.  This code is much faster than most versions
 * of mktime(), anyway.
 */
static int
DetermineTimeZoneOffsetInternal(struct pg_tm *tm, pg_tz *tzp, pg_time_t *tp)
{
  int     date,
        sec;
  pg_time_t day,
        mytime,
        prevtime,
        boundary,
        beforetime,
        aftertime;
  long int  before_gmtoff,
        after_gmtoff;
  int     before_isdst,
        after_isdst;
  int     res;

  /*
   * First, generate the pg_time_t value corresponding to the given
   * y/m/d/h/m/s taken as GMT time.  If this overflows, punt and decide the
   * timezone is GMT.  (For a valid Julian date, integer overflow should be
   * impossible with 64-bit pg_time_t, but let's check for safety.)
   */
  if (!IS_VALID_JULIAN(tm->tm_year, tm->tm_mon, tm->tm_mday))
    goto overflow;
  date = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - UNIX_EPOCH_JDATE;

  day = ((pg_time_t) date) * SECS_PER_DAY;
  if (day / SECS_PER_DAY != date)
    goto overflow;
  sec = tm->tm_sec + (tm->tm_min + tm->tm_hour * MINS_PER_HOUR) * SECS_PER_MINUTE;
  mytime = day + sec;
  /* since sec >= 0, overflow could only be from +day to -mytime */
  if (mytime < 0 && day > 0)
    goto overflow;

  /*
   * Find the DST time boundary just before or following the target time. We
   * assume that all zones have GMT offsets less than 24 hours, and that DST
   * boundaries can't be closer together than 48 hours, so backing up 24
   * hours and finding the "next" boundary will work.
   */
  prevtime = mytime - SECS_PER_DAY;
  if (mytime < 0 && prevtime > 0)
    goto overflow;

  res = pg_next_dst_boundary(&prevtime,
                 &before_gmtoff, &before_isdst,
                 &boundary,
                 &after_gmtoff, &after_isdst,
                 tzp);
  if (res < 0)
    goto overflow;     /* failure? */

  if (res == 0)
  {
    /* Non-DST zone, life is simple */
    tm->tm_isdst = before_isdst;
    *tp = mytime - before_gmtoff;
    return -(int) before_gmtoff;
  }

  /*
   * Form the candidate pg_time_t values with local-time adjustment
   */
  beforetime = mytime - before_gmtoff;
  if ((before_gmtoff > 0 &&
     mytime < 0 && beforetime > 0) ||
    (before_gmtoff <= 0 &&
     mytime > 0 && beforetime < 0))
    goto overflow;
  aftertime = mytime - after_gmtoff;
  if ((after_gmtoff > 0 &&
     mytime < 0 && aftertime > 0) ||
    (after_gmtoff <= 0 &&
     mytime > 0 && aftertime < 0))
    goto overflow;

  /*
   * If both before or both after the boundary time, we know what to do. The
   * boundary time itself is considered to be after the transition, which
   * means we can accept aftertime == boundary in the second case.
   */
  if (beforetime < boundary && aftertime < boundary)
  {
    tm->tm_isdst = before_isdst;
    *tp = beforetime;
    return -(int) before_gmtoff;
  }
  if (beforetime > boundary && aftertime >= boundary)
  {
    tm->tm_isdst = after_isdst;
    *tp = aftertime;
    return -(int) after_gmtoff;
  }

  /*
   * It's an invalid or ambiguous time due to timezone transition.  In a
   * spring-forward transition, prefer the "before" interpretation; in a
   * fall-back transition, prefer "after".  (We used to define and implement
   * this test as "prefer the standard-time interpretation", but that rule
   * does not help to resolve the behavior when both times are reported as
   * standard time; which does happen, eg Europe/Moscow in Oct 2014.  Also,
   * in some zones such as Europe/Dublin, there is widespread confusion
   * about which time offset is "standard" time, so it's fortunate that our
   * behavior doesn't depend on that.)
   */
  if (beforetime > aftertime)
  {
    tm->tm_isdst = before_isdst;
    *tp = beforetime;
    return -(int) before_gmtoff;
  }
  tm->tm_isdst = after_isdst;
  *tp = aftertime;
  return -(int) after_gmtoff;

overflow:
  /* Given date is out of range, so assume UTC */
  tm->tm_isdst = 0;
  *tp = 0;
  return 0;
}


/* DetermineTimeZoneAbbrevOffset()
 *
 * Determine the GMT offset and DST flag to be attributed to a dynamic
 * time zone abbreviation, that is one whose meaning has changed over time.
 * *tm contains the local time at which the meaning should be determined,
 * and tm->tm_isdst receives the DST flag.
 *
 * This differs from the behavior of DetermineTimeZoneOffset() in that a
 * standard-time or daylight-time abbreviation forces use of the corresponding
 * GMT offset even when the zone was then in DS or standard time respectively.
 * (However, that happens only if we can match the given abbreviation to some
 * abbreviation that appears in the IANA timezone data.  Otherwise, we fall
 * back to doing DetermineTimeZoneOffset().)
 */
int
DetermineTimeZoneAbbrevOffset(struct pg_tm *tm, const char *abbr, pg_tz *tzp)
{
  pg_time_t t;
  int     zone_offset;
  int     abbr_offset;
  int     abbr_isdst;

  /*
   * Compute the UTC time we want to probe at.  (In event of overflow, we'll
   * probe at the epoch, which is a bit random but probably doesn't matter.)
   */
  zone_offset = DetermineTimeZoneOffsetInternal(tm, tzp, &t);

  /*
   * Try to match the abbreviation to something in the zone definition.
   */
  if (DetermineTimeZoneAbbrevOffsetInternal(t, abbr, tzp,
                        &abbr_offset, &abbr_isdst))
  {
    /* Success, so use the abbrev-specific answers. */
    tm->tm_isdst = abbr_isdst;
    return abbr_offset;
  }

  /*
   * No match, so use the answers we already got from
   * DetermineTimeZoneOffsetInternal.
   */
  return zone_offset;
}


/* DetermineTimeZoneAbbrevOffsetTS()
 *
 * As above but the probe time is specified as a TimestampTz (hence, UTC time),
 * and DST status is returned into *isdst rather than into tm->tm_isdst.
 */
int
DetermineTimeZoneAbbrevOffsetTS(TimestampTz ts, const char *abbr,
                pg_tz *tzp, int *isdst)
{
  pg_time_t t = timestamptz_to_time_t(ts);
  int     zone_offset;
  int     abbr_offset;
  int     tz;
  struct pg_tm tm;
  fsec_t    fsec;

  /*
   * If the abbrev matches anything in the zone data, this is pretty easy.
   */
  if (DetermineTimeZoneAbbrevOffsetInternal(t, abbr, tzp,
                        &abbr_offset, isdst))
    return abbr_offset;

  /*
   * Else, break down the timestamp so we can use DetermineTimeZoneOffset.
   */
  if (timestamp2tm(ts, &tz, &tm, &fsec, NULL, tzp) != 0)
    ereport(ERROR,
        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
         errmsg("timestamp out of range")));

  zone_offset = DetermineTimeZoneOffset(&tm, tzp);
  *isdst = tm.tm_isdst;
  return zone_offset;
}


/* DetermineTimeZoneAbbrevOffsetInternal()
 *
 * Workhorse for above two functions: work from a pg_time_t probe instant.
 * On success, return GMT offset and DST status into *offset and *isdst.
 */
static bool
DetermineTimeZoneAbbrevOffsetInternal(pg_time_t t, const char *abbr, pg_tz *tzp,
                    int *offset, int *isdst)
{
  char    upabbr[TZ_STRLEN_MAX + 1];
  unsigned char *p;
  long int  gmtoff;

  /* We need to force the abbrev to upper case */
  strlcpy(upabbr, abbr, sizeof(upabbr));
  for (p = (unsigned char *) upabbr; *p; p++)
    *p = pg_toupper(*p);

  /* Look up the abbrev's meaning at this time in this zone */
  if (pg_interpret_timezone_abbrev(upabbr,
                   &t,
                   &gmtoff,
                   isdst,
                   tzp))
  {
    /* Change sign to agree with DetermineTimeZoneOffset() */
    *offset = (int) -gmtoff;
    return true;
  }
  return false;
}


/* TimeZoneAbbrevIsKnown()
 *
 * Detect whether the given string is a time zone abbreviation that's known
 * in the specified TZDB timezone, and if so whether it's fixed or varying
 * meaning.  The match is not case-sensitive.
 */
static bool
TimeZoneAbbrevIsKnown(const char *abbr, pg_tz *tzp,
            bool *isfixed, int *offset, int *isdst)
{
  char    upabbr[TZ_STRLEN_MAX + 1];
  unsigned char *p;
  long int  gmtoff;

  /* We need to force the abbrev to upper case */
  strlcpy(upabbr, abbr, sizeof(upabbr));
  for (p = (unsigned char *) upabbr; *p; p++)
    *p = pg_toupper(*p);

  /* Look up the abbrev's meaning in this zone */
  if (pg_timezone_abbrev_is_known(upabbr,
                  isfixed,
                  &gmtoff,
                  isdst,
                  tzp))
  {
    /* Change sign to agree with DetermineTimeZoneOffset() */
    *offset = (int) -gmtoff;
    return true;
  }
  return false;
}


/* DecodeTimeOnly()
 * Interpret parsed string as time fields only.
 * Returns 0 if successful, DTERR code if bogus input detected.
 *
 * Inputs are field[] and ftype[] arrays, of length nf.
 * Other arguments are outputs.
 *
 * Note that support for time zone is here for
 * SQL TIME WITH TIME ZONE, but it reveals
 * bogosity with SQL date/time standards, since
 * we must infer a time zone from current time.
 * - thomas 2000-03-10
 * Allow specifying date to get a better time zone,
 * if time zones are allowed. - thomas 2001-12-26
 */
int
DecodeTimeOnly(char **field, int *ftype, int nf,
         int *dtype, struct pg_tm *tm, fsec_t *fsec, int *tzp,
         DateTimeErrorExtra *extra)
{
  int     fmask = 0,
        tmask,
        type;
  int     ptype = 0;    /* "prefix type" for ISO and Julian formats */
  int     i;
  int     val;
  int     dterr;
  bool    isjulian = false;
  bool    is2digits = false;
  bool    bc = false;
  int     mer = HR24;
  pg_tz    *namedTz = NULL;
  pg_tz    *abbrevTz = NULL;
  char     *abbrev = NULL;
  pg_tz    *valtz;

  *dtype = DTK_TIME;
  tm->tm_hour = 0;
  tm->tm_min = 0;
  tm->tm_sec = 0;
  *fsec = 0;
  /* don't know daylight savings time status apriori */
  tm->tm_isdst = -1;

  if (tzp != NULL)
    *tzp = 0;

  for (i = 0; i < nf; i++)
  {
    switch (ftype[i])
    {
      case DTK_DATE:

        /*
         * Time zone not allowed? Then should not accept dates or time
         * zones no matter what else!
         */
        if (tzp == NULL)
          return DTERR_BAD_FORMAT;

        /* Under limited circumstances, we will accept a date... */
        if (i == 0 && nf >= 2 &&
          (ftype[nf - 1] == DTK_DATE || ftype[1] == DTK_TIME))
        {
          dterr = DecodeDate(field[i], fmask,
                     &tmask, &is2digits, tm);
          if (dterr)
            return dterr;
        }
        /* otherwise, this is a time and/or time zone */
        else
        {
          if (isdigit((unsigned char) *field[i]))
          {
            char     *cp;

            /*
             * Starts with a digit but we already have a time
             * field? Then we are in trouble with time already...
             */
            if ((fmask & DTK_TIME_M) == DTK_TIME_M)
              return DTERR_BAD_FORMAT;

            /*
             * Should not get here and fail. Sanity check only...
             */
            if ((cp = strchr(field[i], '-')) == NULL)
              return DTERR_BAD_FORMAT;

            /* Get the time zone from the end of the string */
            dterr = DecodeTimezone(cp, tzp);
            if (dterr)
              return dterr;
            *cp = '\0';

            /*
             * Then read the rest of the field as a concatenated
             * time
             */
            dterr = DecodeNumberField(strlen(field[i]), field[i],
                          (fmask | DTK_DATE_M),
                          &tmask, tm,
                          fsec, &is2digits);
            if (dterr < 0)
              return dterr;
            ftype[i] = dterr;

            tmask |= DTK_M(TZ);
          }
          else
          {
            namedTz = pg_tzset(field[i]);
            if (!namedTz)
            {
              extra->dtee_timezone = field[i];
              return DTERR_BAD_TIMEZONE;
            }
            /* we'll apply the zone setting below */
            ftype[i] = DTK_TZ;
            tmask = DTK_M(TZ);
          }
        }
        break;

      case DTK_TIME:

        /*
         * This might be an ISO time following a "t" field.
         */
        if (ptype != 0)
        {
          if (ptype != DTK_TIME)
            return DTERR_BAD_FORMAT;
          ptype = 0;
        }

        dterr = DecodeTime(field[i], (fmask | DTK_DATE_M),
                   INTERVAL_FULL_RANGE,
                   &tmask, tm, fsec);
        if (dterr)
          return dterr;
        break;

      case DTK_TZ:
        {
          int     tz;

          if (tzp == NULL)
            return DTERR_BAD_FORMAT;

          dterr = DecodeTimezone(field[i], &tz);
          if (dterr)
            return dterr;
          *tzp = tz;
          tmask = DTK_M(TZ);
        }
        break;

      case DTK_NUMBER:

        /*
         * Deal with cases where previous field labeled this one
         */
        if (ptype != 0)
        {
          char     *cp;
          int     value;

          errno = 0;
          value = strtoint(field[i], &cp, 10);
          if (errno == ERANGE)
            return DTERR_FIELD_OVERFLOW;
          if (*cp != '.' && *cp != '\0')
            return DTERR_BAD_FORMAT;

          switch (ptype)
          {
            case DTK_JULIAN:
              /* previous field was a label for "julian date" */
              if (tzp == NULL)
                return DTERR_BAD_FORMAT;
              if (value < 0)
                return DTERR_FIELD_OVERFLOW;
              tmask = DTK_DATE_M;
              j2date(value, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
              isjulian = true;

              if (*cp == '.')
              {
                double    time;

                dterr = ParseFraction(cp, &time);
                if (dterr)
                  return dterr;
                time *= USECS_PER_DAY;
                dt2time(time,
                    &tm->tm_hour, &tm->tm_min,
                    &tm->tm_sec, fsec);
                tmask |= DTK_TIME_M;
              }
              break;

            case DTK_TIME:
              /* previous field was "t" for ISO time */
              dterr = DecodeNumberField(strlen(field[i]), field[i],
                            (fmask | DTK_DATE_M),
                            &tmask, tm,
                            fsec, &is2digits);
              if (dterr < 0)
                return dterr;
              ftype[i] = dterr;

              if (tmask != DTK_TIME_M)
                return DTERR_BAD_FORMAT;
              break;

            default:
              return DTERR_BAD_FORMAT;
              break;
          }

          ptype = 0;
          *dtype = DTK_DATE;
        }
        else
        {
          char     *cp;
          int     flen;

          flen = strlen(field[i]);
          cp = strchr(field[i], '.');

          /* Embedded decimal? */
          if (cp != NULL)
          {
            /*
             * Under limited circumstances, we will accept a
             * date...
             */
            if (i == 0 && nf >= 2 && ftype[nf - 1] == DTK_DATE)
            {
              dterr = DecodeDate(field[i], fmask,
                         &tmask, &is2digits, tm);
              if (dterr)
                return dterr;
            }
            /* embedded decimal and several digits before? */
            else if (flen - strlen(cp) > 2)
            {
              /*
               * Interpret as a concatenated date or time Set
               * the type field to allow decoding other fields
               * later. Example: 20011223 or 040506
               */
              dterr = DecodeNumberField(flen, field[i],
                            (fmask | DTK_DATE_M),
                            &tmask, tm,
                            fsec, &is2digits);
              if (dterr < 0)
                return dterr;
              ftype[i] = dterr;
            }
            else
              return DTERR_BAD_FORMAT;
          }
          else if (flen > 4)
          {
            dterr = DecodeNumberField(flen, field[i],
                          (fmask | DTK_DATE_M),
                          &tmask, tm,
                          fsec, &is2digits);
            if (dterr < 0)
              return dterr;
            ftype[i] = dterr;
          }
          /* otherwise it is a single date/time field... */
          else
          {
            dterr = DecodeNumber(flen, field[i],
                       false,
                       (fmask | DTK_DATE_M),
                       &tmask, tm,
                       fsec, &is2digits);
            if (dterr)
              return dterr;
          }
        }
        break;

      case DTK_STRING:
      case DTK_SPECIAL:
        /* timezone abbrevs take precedence over built-in tokens */
        dterr = DecodeTimezoneAbbrev(i, field[i],
                       &type, &val, &valtz, extra);
        if (dterr)
          return dterr;
        if (type == UNKNOWN_FIELD)
          type = DecodeSpecial(i, field[i], &val);
        if (type == IGNORE_DTF)
          continue;

        tmask = DTK_M(type);
        switch (type)
        {
          case RESERV:
            switch (val)
            {
              case DTK_NOW:
                tmask = DTK_TIME_M;
                *dtype = DTK_TIME;
                GetCurrentTimeUsec(tm, fsec, NULL);
                break;

              case DTK_ZULU:
                tmask = (DTK_TIME_M | DTK_M(TZ));
                *dtype = DTK_TIME;
                tm->tm_hour = 0;
                tm->tm_min = 0;
                tm->tm_sec = 0;
                tm->tm_isdst = 0;
                break;

              default:
                return DTERR_BAD_FORMAT;
            }

            break;

          case DTZMOD:

            /*
             * daylight savings time modifier (solves "MET DST"
             * syntax)
             */
            tmask |= DTK_M(DTZ);
            tm->tm_isdst = 1;
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            *tzp -= val;
            break;

          case DTZ:

            /*
             * set mask for TZ here _or_ check for DTZ later when
             * getting default timezone
             */
            tmask |= DTK_M(TZ);
            tm->tm_isdst = 1;
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            *tzp = -val;
            ftype[i] = DTK_TZ;
            break;

          case TZ:
            tm->tm_isdst = 0;
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            *tzp = -val;
            ftype[i] = DTK_TZ;
            break;

          case DYNTZ:
            tmask |= DTK_M(TZ);
            if (tzp == NULL)
              return DTERR_BAD_FORMAT;
            /* we'll determine the actual offset later */
            abbrevTz = valtz;
            abbrev = field[i];
            ftype[i] = DTK_TZ;
            break;

          case AMPM:
            mer = val;
            break;

          case ADBC:
            bc = (val == BC);
            break;

          case UNITS:
            tmask = 0;
            /* reject consecutive unhandled units */
            if (ptype != 0)
              return DTERR_BAD_FORMAT;
            ptype = val;
            break;

          case ISOTIME:
            tmask = 0;
            /* reject consecutive unhandled units */
            if (ptype != 0)
              return DTERR_BAD_FORMAT;
            ptype = val;
            break;

          case UNKNOWN_FIELD:

            /*
             * Before giving up and declaring error, check to see
             * if it is an all-alpha timezone name.
             */
            namedTz = pg_tzset(field[i]);
            if (!namedTz)
              return DTERR_BAD_FORMAT;
            /* we'll apply the zone setting below */
            tmask = DTK_M(TZ);
            break;

          default:
            return DTERR_BAD_FORMAT;
        }
        break;

      default:
        return DTERR_BAD_FORMAT;
    }

    if (tmask & fmask)
      return DTERR_BAD_FORMAT;
    fmask |= tmask;
  }              /* end loop over fields */

  /* reject if prefix type appeared and was never handled */
  if (ptype != 0)
    return DTERR_BAD_FORMAT;

  /* do final checking/adjustment of Y/M/D fields */
  dterr = ValidateDate(fmask, isjulian, is2digits, bc, tm);
  if (dterr)
    return dterr;

  /* handle AM/PM */
  if (mer != HR24 && tm->tm_hour > HOURS_PER_DAY / 2)
    return DTERR_FIELD_OVERFLOW;
  if (mer == AM && tm->tm_hour == HOURS_PER_DAY / 2)
    tm->tm_hour = 0;
  else if (mer == PM && tm->tm_hour != HOURS_PER_DAY / 2)
    tm->tm_hour += HOURS_PER_DAY / 2;

  /* check for time overflow */
  if (time_overflows(tm->tm_hour, tm->tm_min, tm->tm_sec, *fsec))
    return DTERR_FIELD_OVERFLOW;

  if ((fmask & DTK_TIME_M) != DTK_TIME_M)
    return DTERR_BAD_FORMAT;

  /*
   * If we had a full timezone spec, compute the offset (we could not do it
   * before, because we may need the date to resolve DST status).
   */
  if (namedTz != NULL)
  {
    long int  gmtoff;

    /* daylight savings time modifier disallowed with full TZ */
    if (fmask & DTK_M(DTZMOD))
      return DTERR_BAD_FORMAT;

    /* if non-DST zone, we do not need to know the date */
    if (pg_get_timezone_offset(namedTz, &gmtoff))
    {
      *tzp = -(int) gmtoff;
    }
    else
    {
      /* a date has to be specified */
      if ((fmask & DTK_DATE_M) != DTK_DATE_M)
        return DTERR_BAD_FORMAT;
      *tzp = DetermineTimeZoneOffset(tm, namedTz);
    }
  }

  /*
   * Likewise, if we had a dynamic timezone abbreviation, resolve it now.
   */
  if (abbrevTz != NULL)
  {
    struct pg_tm tt,
           *tmp = &tt;

    /*
     * daylight savings time modifier but no standard timezone? then error
     */
    if (fmask & DTK_M(DTZMOD))
      return DTERR_BAD_FORMAT;

    if ((fmask & DTK_DATE_M) == 0)
      GetCurrentDateTime(tmp);
    else
    {
      /* a date has to be specified */
      if ((fmask & DTK_DATE_M) != DTK_DATE_M)
        return DTERR_BAD_FORMAT;
      tmp->tm_year = tm->tm_year;
      tmp->tm_mon = tm->tm_mon;
      tmp->tm_mday = tm->tm_mday;
    }
    tmp->tm_hour = tm->tm_hour;
    tmp->tm_min = tm->tm_min;
    tmp->tm_sec = tm->tm_sec;
    *tzp = DetermineTimeZoneAbbrevOffset(tmp, abbrev, abbrevTz);
    tm->tm_isdst = tmp->tm_isdst;
  }

  /* timezone not specified? then use session timezone */
  if (tzp != NULL && !(fmask & DTK_M(TZ)))
  {
    struct pg_tm tt,
           *tmp = &tt;

    /*
     * daylight savings time modifier but no standard timezone? then error
     */
    if (fmask & DTK_M(DTZMOD))
      return DTERR_BAD_FORMAT;

    if ((fmask & DTK_DATE_M) == 0)
      GetCurrentDateTime(tmp);
    else
    {
      /* a date has to be specified */
      if ((fmask & DTK_DATE_M) != DTK_DATE_M)
        return DTERR_BAD_FORMAT;
      tmp->tm_year = tm->tm_year;
      tmp->tm_mon = tm->tm_mon;
      tmp->tm_mday = tm->tm_mday;
    }
    tmp->tm_hour = tm->tm_hour;
    tmp->tm_min = tm->tm_min;
    tmp->tm_sec = tm->tm_sec;
    *tzp = DetermineTimeZoneOffset(tmp, session_timezone);
    tm->tm_isdst = tmp->tm_isdst;
  }

  return 0;
}

/* DecodeDate()
 * Decode date string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 *
 *  str: field to be parsed
 *  fmask: bitmask for field types already seen
 *  *tmask: receives bitmask for fields found here
 *  *is2digits: set to true if we find 2-digit year
 *  *tm: field values are stored into appropriate members of this struct
 */
static int
DecodeDate(char *str, int fmask, int *tmask, bool *is2digits,
       struct pg_tm *tm)
{
  fsec_t    fsec;
  int     nf = 0;
  int     i,
        len;
  int     dterr;
  bool    haveTextMonth = false;
  int     type,
        val,
        dmask = 0;
  char     *field[MAXDATEFIELDS];

  *tmask = 0;

  /* parse this string... */
  while (*str != '\0' && nf < MAXDATEFIELDS)
  {
    /* skip field separators */
    while (*str != '\0' && !isalnum((unsigned char) *str))
      str++;

    if (*str == '\0')
      return DTERR_BAD_FORMAT; /* end of string after separator */

    field[nf] = str;
    if (isdigit((unsigned char) *str))
    {
      while (isdigit((unsigned char) *str))
        str++;
    }
    else if (isalpha((unsigned char) *str))
    {
      while (isalpha((unsigned char) *str))
        str++;
    }

    /* Just get rid of any non-digit, non-alpha characters... */
    if (*str != '\0')
      *str++ = '\0';
    nf++;
  }

  /* look first for text fields, since that will be unambiguous month */
  for (i = 0; i < nf; i++)
  {
    if (isalpha((unsigned char) *field[i]))
    {
      type = DecodeSpecial(i, field[i], &val);
      if (type == IGNORE_DTF)
        continue;

      dmask = DTK_M(type);
      switch (type)
      {
        case MONTH:
          tm->tm_mon = val;
          haveTextMonth = true;
          break;

        default:
          return DTERR_BAD_FORMAT;
      }
      if (fmask & dmask)
        return DTERR_BAD_FORMAT;

      fmask |= dmask;
      *tmask |= dmask;

      /* mark this field as being completed */
      field[i] = NULL;
    }
  }

  /* now pick up remaining numeric fields */
  for (i = 0; i < nf; i++)
  {
    if (field[i] == NULL)
      continue;

    if ((len = strlen(field[i])) <= 0)
      return DTERR_BAD_FORMAT;

    dterr = DecodeNumber(len, field[i], haveTextMonth, fmask,
               &dmask, tm,
               &fsec, is2digits);
    if (dterr)
      return dterr;

    if (fmask & dmask)
      return DTERR_BAD_FORMAT;

    fmask |= dmask;
    *tmask |= dmask;
  }

  if ((fmask & ~(DTK_M(DOY) | DTK_M(TZ))) != DTK_DATE_M)
    return DTERR_BAD_FORMAT;

  /* validation of the field values must wait until ValidateDate() */

  return 0;
}

/* ValidateDate()
 * Check valid year/month/day values, handle BC and DOY cases
 * Return 0 if okay, a DTERR code if not.
 */
int
ValidateDate(int fmask, bool isjulian, bool is2digits, bool bc,
       struct pg_tm *tm)
{
  if (fmask & DTK_M(YEAR))
  {
    if (isjulian)
    {
      /* tm_year is correct and should not be touched */
    }
    else if (bc)
    {
      /* there is no year zero in AD/BC notation */
      if (tm->tm_year <= 0)
        return DTERR_FIELD_OVERFLOW;
      /* internally, we represent 1 BC as year zero, 2 BC as -1, etc */
      tm->tm_year = -(tm->tm_year - 1);
    }
    else if (is2digits)
    {
      /* process 1 or 2-digit input as 1970-2069 AD, allow '0' and '00' */
      if (tm->tm_year < 0) /* just paranoia */
        return DTERR_FIELD_OVERFLOW;
      if (tm->tm_year < 70)
        tm->tm_year += 2000;
      else if (tm->tm_year < 100)
        tm->tm_year += 1900;
    }
    else
    {
      /* there is no year zero in AD/BC notation */
      if (tm->tm_year <= 0)
        return DTERR_FIELD_OVERFLOW;
    }
  }

  /* now that we have correct year, decode DOY */
  if (fmask & DTK_M(DOY))
  {
    j2date(date2j(tm->tm_year, 1, 1) + tm->tm_yday - 1,
         &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
  }

  /* check for valid month */
  if (fmask & DTK_M(MONTH))
  {
    if (tm->tm_mon < 1 || tm->tm_mon > MONTHS_PER_YEAR)
      return DTERR_MD_FIELD_OVERFLOW;
  }

  /* minimal check for valid day */
  if (fmask & DTK_M(DAY))
  {
    if (tm->tm_mday < 1 || tm->tm_mday > 31)
      return DTERR_MD_FIELD_OVERFLOW;
  }

  if ((fmask & DTK_DATE_M) == DTK_DATE_M)
  {
    /*
     * Check for valid day of month, now that we know for sure the month
     * and year.  Note we don't use MD_FIELD_OVERFLOW here, since it seems
     * unlikely that "Feb 29" is a YMD-order error.
     */
    if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
      return DTERR_FIELD_OVERFLOW;
  }

  return 0;
}


/* DecodeTimeCommon()
 * Decode time string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 * tmask and itm are output parameters.
 *
 * This code is shared between the timestamp and interval cases.
 * We return a struct pg_itm (of which only the tm_usec, tm_sec, tm_min,
 * and tm_hour fields are used) and let the wrapper functions below
 * convert and range-check as necessary.
 */
static int
DecodeTimeCommon(char *str, int fmask, int range,
         int *tmask, struct pg_itm *itm)
{
  char     *cp;
  int     dterr;
  fsec_t    fsec = 0;

  *tmask = DTK_TIME_M;

  errno = 0;
  itm->tm_hour = strtoi64(str, &cp, 10);
  if (errno == ERANGE)
    return DTERR_FIELD_OVERFLOW;
  if (*cp != ':')
    return DTERR_BAD_FORMAT;
  errno = 0;
  itm->tm_min = strtoint(cp + 1, &cp, 10);
  if (errno == ERANGE)
    return DTERR_FIELD_OVERFLOW;
  if (*cp == '\0')
  {
    itm->tm_sec = 0;
    /* If it's a MINUTE TO SECOND interval, take 2 fields as being mm:ss */
    if (range == (INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND)))
    {
      if (itm->tm_hour > INT_MAX || itm->tm_hour < INT_MIN)
        return DTERR_FIELD_OVERFLOW;
      itm->tm_sec = itm->tm_min;
      itm->tm_min = (int) itm->tm_hour;
      itm->tm_hour = 0;
    }
  }
  else if (*cp == '.')
  {
    /* always assume mm:ss.sss is MINUTE TO SECOND */
    dterr = ParseFractionalSecond(cp, &fsec);
    if (dterr)
      return dterr;
    if (itm->tm_hour > INT_MAX || itm->tm_hour < INT_MIN)
      return DTERR_FIELD_OVERFLOW;
    itm->tm_sec = itm->tm_min;
    itm->tm_min = (int) itm->tm_hour;
    itm->tm_hour = 0;
  }
  else if (*cp == ':')
  {
    errno = 0;
    itm->tm_sec = strtoint(cp + 1, &cp, 10);
    if (errno == ERANGE)
      return DTERR_FIELD_OVERFLOW;
    if (*cp == '.')
    {
      dterr = ParseFractionalSecond(cp, &fsec);
      if (dterr)
        return dterr;
    }
    else if (*cp != '\0')
      return DTERR_BAD_FORMAT;
  }
  else
    return DTERR_BAD_FORMAT;

  /* do a sanity check; but caller must check the range of tm_hour */
  if (itm->tm_hour < 0 ||
    itm->tm_min < 0 || itm->tm_min > MINS_PER_HOUR - 1 ||
    itm->tm_sec < 0 || itm->tm_sec > SECS_PER_MINUTE ||
    fsec < 0 || fsec > USECS_PER_SEC)
    return DTERR_FIELD_OVERFLOW;

  itm->tm_usec = (int) fsec;

  return 0;
}

/* DecodeTime()
 * Decode time string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 *
 * This version is used for timestamps.  The results are returned into
 * the tm_hour/tm_min/tm_sec fields of *tm, and microseconds into *fsec.
 */
static int
DecodeTime(char *str, int fmask, int range,
       int *tmask, struct pg_tm *tm, fsec_t *fsec)
{
  struct pg_itm itm;
  int     dterr;

  dterr = DecodeTimeCommon(str, fmask, range,
               tmask, &itm);
  if (dterr)
    return dterr;

  if (itm.tm_hour > INT_MAX)
    return DTERR_FIELD_OVERFLOW;
  tm->tm_hour = (int) itm.tm_hour;
  tm->tm_min = itm.tm_min;
  tm->tm_sec = itm.tm_sec;
  *fsec = itm.tm_usec;

  return 0;
}

/* DecodeTimeForInterval()
 * Decode time string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 *
 * This version is used for intervals.  The results are returned into
 * itm_in->tm_usec.
 */
static int
DecodeTimeForInterval(char *str, int fmask, int range,
            int *tmask, struct pg_itm_in *itm_in)
{
  struct pg_itm itm;
  int     dterr;

  dterr = DecodeTimeCommon(str, fmask, range,
               tmask, &itm);
  if (dterr)
    return dterr;

  itm_in->tm_usec = itm.tm_usec;
  if (!int64_multiply_add(itm.tm_hour, USECS_PER_HOUR, &itm_in->tm_usec) ||
    !int64_multiply_add(itm.tm_min, USECS_PER_MINUTE, &itm_in->tm_usec) ||
    !int64_multiply_add(itm.tm_sec, USECS_PER_SEC, &itm_in->tm_usec))
    return DTERR_FIELD_OVERFLOW;

  return 0;
}


/* DecodeNumber()
 * Interpret plain numeric field as a date value in context.
 * Return 0 if okay, a DTERR code if not.
 */
static int
DecodeNumber(int flen, char *str, bool haveTextMonth, int fmask,
       int *tmask, struct pg_tm *tm, fsec_t *fsec, bool *is2digits)
{
  int     val;
  char     *cp;
  int     dterr;

  *tmask = 0;

  errno = 0;
  val = strtoint(str, &cp, 10);
  if (errno == ERANGE)
    return DTERR_FIELD_OVERFLOW;
  if (cp == str)
    return DTERR_BAD_FORMAT;

  if (*cp == '.')
  {
    /*
     * More than two digits before decimal point? Then could be a date or
     * a run-together time: 2001.360 20011225 040506.789
     */
    if (cp - str > 2)
    {
      dterr = DecodeNumberField(flen, str,
                    (fmask | DTK_DATE_M),
                    tmask, tm,
                    fsec, is2digits);
      if (dterr < 0)
        return dterr;
      return 0;
    }

    dterr = ParseFractionalSecond(cp, fsec);
    if (dterr)
      return dterr;
  }
  else if (*cp != '\0')
    return DTERR_BAD_FORMAT;

  /* Special case for day of year */
  if (flen == 3 && (fmask & DTK_DATE_M) == DTK_M(YEAR) && val >= 1 &&
    val <= 366)
  {
    *tmask = (DTK_M(DOY) | DTK_M(MONTH) | DTK_M(DAY));
    tm->tm_yday = val;
    /* tm_mon and tm_mday can't actually be set yet ... */
    return 0;
  }

  /* Switch based on what we have so far */
  switch (fmask & DTK_DATE_M)
  {
    case 0:

      /*
       * Nothing so far; make a decision about what we think the input
       * is.  There used to be lots of heuristics here, but the
       * consensus now is to be paranoid.  It *must* be either
       * YYYY-MM-DD (with a more-than-two-digit year field), or the
       * field order defined by DateOrder.
       */
      if (flen >= 3 || DateOrder == DATEORDER_YMD)
      {
        *tmask = DTK_M(YEAR);
        tm->tm_year = val;
      }
      else if (DateOrder == DATEORDER_DMY)
      {
        *tmask = DTK_M(DAY);
        tm->tm_mday = val;
      }
      else
      {
        *tmask = DTK_M(MONTH);
        tm->tm_mon = val;
      }
      break;

    case (DTK_M(YEAR)):
      /* Must be at second field of YY-MM-DD */
      *tmask = DTK_M(MONTH);
      tm->tm_mon = val;
      break;

    case (DTK_M(MONTH)):
      if (haveTextMonth)
      {
        /*
         * We are at the first numeric field of a date that included a
         * textual month name.  We want to support the variants
         * MON-DD-YYYY, DD-MON-YYYY, and YYYY-MON-DD as unambiguous
         * inputs.  We will also accept MON-DD-YY or DD-MON-YY in
         * either DMY or MDY modes, as well as YY-MON-DD in YMD mode.
         */
        if (flen >= 3 || DateOrder == DATEORDER_YMD)
        {
          *tmask = DTK_M(YEAR);
          tm->tm_year = val;
        }
        else
        {
          *tmask = DTK_M(DAY);
          tm->tm_mday = val;
        }
      }
      else
      {
        /* Must be at second field of MM-DD-YY */
        *tmask = DTK_M(DAY);
        tm->tm_mday = val;
      }
      break;

    case (DTK_M(YEAR) | DTK_M(MONTH)):
      if (haveTextMonth)
      {
        /* Need to accept DD-MON-YYYY even in YMD mode */
        if (flen >= 3 && *is2digits)
        {
          /* Guess that first numeric field is day was wrong */
          *tmask = DTK_M(DAY);  /* YEAR is already set */
          tm->tm_mday = tm->tm_year;
          tm->tm_year = val;
          *is2digits = false;
        }
        else
        {
          *tmask = DTK_M(DAY);
          tm->tm_mday = val;
        }
      }
      else
      {
        /* Must be at third field of YY-MM-DD */
        *tmask = DTK_M(DAY);
        tm->tm_mday = val;
      }
      break;

    case (DTK_M(DAY)):
      /* Must be at second field of DD-MM-YY */
      *tmask = DTK_M(MONTH);
      tm->tm_mon = val;
      break;

    case (DTK_M(MONTH) | DTK_M(DAY)):
      /* Must be at third field of DD-MM-YY or MM-DD-YY */
      *tmask = DTK_M(YEAR);
      tm->tm_year = val;
      break;

    case (DTK_M(YEAR) | DTK_M(MONTH) | DTK_M(DAY)):
      /* we have all the date, so it must be a time field */
      dterr = DecodeNumberField(flen, str, fmask,
                    tmask, tm,
                    fsec, is2digits);
      if (dterr < 0)
        return dterr;
      return 0;

    default:
      /* Anything else is bogus input */
      return DTERR_BAD_FORMAT;
  }

  /*
   * When processing a year field, mark it for adjustment if it's only one
   * or two digits.
   */
  if (*tmask == DTK_M(YEAR))
    *is2digits = (flen <= 2);

  return 0;
}


/* DecodeNumberField()
 * Interpret numeric string as a concatenated date or time field.
 * Return a DTK token (>= 0) if successful, a DTERR code (< 0) if not.
 *
 * Use the context of previously decoded fields to help with
 * the interpretation.
 */
static int
DecodeNumberField(int len, char *str, int fmask,
          int *tmask, struct pg_tm *tm, fsec_t *fsec, bool *is2digits)
{
  char     *cp;

  /*
   * This function was originally meant to cope only with DTK_NUMBER fields,
   * but we now sometimes abuse it to parse (parts of) DTK_DATE fields,
   * which can contain letters and other punctuation.  Reject if it's not a
   * valid DTK_NUMBER, that is digits and decimal point(s).  (ParseFraction
   * will reject if there's more than one decimal point.)
   */
  if (strspn(str, "0123456789.") != len)
    return DTERR_BAD_FORMAT;

  /*
   * Have a decimal point? Then this is a date or something with a seconds
   * field...
   */
  if ((cp = strchr(str, '.')) != NULL)
  {
    int     dterr;

    /* Convert the fraction and store at *fsec */
    dterr = ParseFractionalSecond(cp, fsec);
    if (dterr)
      return dterr;
    /* Now truncate off the fraction for further processing */
    *cp = '\0';
    len = strlen(str);
  }
  /* No decimal point and no complete date yet? */
  else if ((fmask & DTK_DATE_M) != DTK_DATE_M)
  {
    if (len >= 6)
    {
      *tmask = DTK_DATE_M;

      /*
       * Start from end and consider first 2 as Day, next 2 as Month,
       * and the rest as Year.
       */
      tm->tm_mday = atoi(str + (len - 2));
      *(str + (len - 2)) = '\0';
      tm->tm_mon = atoi(str + (len - 4));
      *(str + (len - 4)) = '\0';
      tm->tm_year = atoi(str);
      if ((len - 4) == 2)
        *is2digits = true;

      return DTK_DATE;
    }
  }

  /* not all time fields are specified? */
  if ((fmask & DTK_TIME_M) != DTK_TIME_M)
  {
    /* hhmmss */
    if (len == 6)
    {
      *tmask = DTK_TIME_M;
      tm->tm_sec = atoi(str + 4);
      *(str + 4) = '\0';
      tm->tm_min = atoi(str + 2);
      *(str + 2) = '\0';
      tm->tm_hour = atoi(str);

      return DTK_TIME;
    }
    /* hhmm? */
    else if (len == 4)
    {
      *tmask = DTK_TIME_M;
      tm->tm_sec = 0;
      tm->tm_min = atoi(str + 2);
      *(str + 2) = '\0';
      tm->tm_hour = atoi(str);

      return DTK_TIME;
    }
  }

  return DTERR_BAD_FORMAT;
}


/* DecodeTimezone()
 * Interpret string as a numeric timezone.
 *
 * Return 0 if okay (and set *tzp), a DTERR code if not okay.
 */
int
DecodeTimezone(const char *str, int *tzp)
{
  int     tz;
  int     hr,
        min,
        sec = 0;
  char     *cp;

  /* leading character must be "+" or "-" */
  if (*str != '+' && *str != '-')
    return DTERR_BAD_FORMAT;

  errno = 0;
  hr = strtoint(str + 1, &cp, 10);
  if (errno == ERANGE)
    return DTERR_TZDISP_OVERFLOW;

  /* explicit delimiter? */
  if (*cp == ':')
  {
    errno = 0;
    min = strtoint(cp + 1, &cp, 10);
    if (errno == ERANGE)
      return DTERR_TZDISP_OVERFLOW;
    if (*cp == ':')
    {
      errno = 0;
      sec = strtoint(cp + 1, &cp, 10);
      if (errno == ERANGE)
        return DTERR_TZDISP_OVERFLOW;
    }
  }
  /* otherwise, might have run things together... */
  else if (*cp == '\0' && strlen(str) > 3)
  {
    min = hr % 100;
    hr = hr / 100;
    /* we could, but don't, support a run-together hhmmss format */
  }
  else
    min = 0;

  /* Range-check the values; see notes in datatype/timestamp.h */
  if (hr < 0 || hr > MAX_TZDISP_HOUR)
    return DTERR_TZDISP_OVERFLOW;
  if (min < 0 || min >= MINS_PER_HOUR)
    return DTERR_TZDISP_OVERFLOW;
  if (sec < 0 || sec >= SECS_PER_MINUTE)
    return DTERR_TZDISP_OVERFLOW;

  tz = (hr * MINS_PER_HOUR + min) * SECS_PER_MINUTE + sec;
  if (*str == '-')
    tz = -tz;

  *tzp = -tz;

  if (*cp != '\0')
    return DTERR_BAD_FORMAT;

  return 0;
}


/* DecodeTimezoneAbbrev()
 * Interpret string as a timezone abbreviation, if possible.
 *
 * Sets *ftype to an abbreviation type (TZ, DTZ, or DYNTZ), or UNKNOWN_FIELD if
 * string is not any known abbreviation.  On success, set *offset and *tz to
 * represent the UTC offset (for TZ or DTZ) or underlying zone (for DYNTZ).
 * Note that full timezone names (such as America/New_York) are not handled
 * here, mostly for historical reasons.
 *
 * The function result is 0 or a DTERR code; in the latter case, *extra
 * is filled as needed.  Note that unknown-abbreviation is not considered
 * an error case.  Also note that many callers assume that the DTERR code
 * is one that DateTimeParseError does not require "str" or "datatype"
 * strings for.
 *
 * Given string must be lowercased already.
 *
 * Implement a cache lookup since it is likely that dates
 *  will be related in format.
 */
int
DecodeTimezoneAbbrev(int field, const char *lowtoken,
           int *ftype, int *offset, pg_tz **tz,
           DateTimeErrorExtra *extra)
{
  TzAbbrevCache *tzc = &tzabbrevcache[field];
  bool    isfixed;
  int     isdst;
  const datetkn *tp;

  /*
   * Do we have a cached result?  Use strncmp so that we match truncated
   * names, although we shouldn't really see that happen with normal
   * abbreviations.
   */
  if (strncmp(lowtoken, tzc->abbrev, TOKMAXLEN) == 0)
  {
    *ftype = tzc->ftype;
    *offset = tzc->offset;
    *tz = tzc->tz;
    return 0;
  }

  /*
   * See if the current session_timezone recognizes it.  Checking this
   * before zoneabbrevtbl allows us to correctly handle abbreviations whose
   * meaning varies across zones, such as "LMT".
   */
  if (session_timezone &&
    TimeZoneAbbrevIsKnown(lowtoken, session_timezone,
                &isfixed, offset, &isdst))
  {
    *ftype = (isfixed ? (isdst ? DTZ : TZ) : DYNTZ);
    *tz = (isfixed ? NULL : session_timezone);
    /* flip sign to agree with the convention used in zoneabbrevtbl */
    *offset = -(*offset);
    /* cache result; use strlcpy to truncate name if necessary */
    strlcpy(tzc->abbrev, lowtoken, TOKMAXLEN + 1);
    tzc->ftype = *ftype;
    tzc->offset = *offset;
    tzc->tz = *tz;
    return 0;
  }

  /* Nope, so look in zoneabbrevtbl */
  if (zoneabbrevtbl)
    tp = datebsearch(lowtoken, zoneabbrevtbl->abbrevs,
             zoneabbrevtbl->numabbrevs);
  else
    tp = NULL;
  if (tp == NULL)
  {
    *ftype = UNKNOWN_FIELD;
    *offset = 0;
    *tz = NULL;
    /* failure results are not cached */
  }
  else
  {
    *ftype = tp->type;
    if (tp->type == DYNTZ)
    {
      *offset = 0;
      *tz = FetchDynamicTimeZone(zoneabbrevtbl, tp, extra);
      if (*tz == NULL)
        return DTERR_BAD_ZONE_ABBREV;
    }
    else
    {
      *offset = tp->value;
      *tz = NULL;
    }

    /* cache result; use strlcpy to truncate name if necessary */
    strlcpy(tzc->abbrev, lowtoken, TOKMAXLEN + 1);
    tzc->ftype = *ftype;
    tzc->offset = *offset;
    tzc->tz = *tz;
  }

  return 0;
}

/*
 * Reset tzabbrevcache after a change in session_timezone.
 */
void
ClearTimeZoneAbbrevCache(void)
{
  memset(tzabbrevcache, 0, sizeof(tzabbrevcache));
}


/* DecodeSpecial()
 * Decode text string using lookup table.
 *
 * Recognizes the keywords listed in datetktbl.
 * Note: at one time this would also recognize timezone abbreviations,
 * but no more; use DecodeTimezoneAbbrev for that.
 *
 * Given string must be lowercased already.
 *
 * Implement a cache lookup since it is likely that dates
 *  will be related in format.
 */
int
DecodeSpecial(int field, const char *lowtoken, int *val)
{
  int     type;
  const datetkn *tp;

  tp = datecache[field];
  /* use strncmp so that we match truncated tokens */
  if (tp == NULL || strncmp(lowtoken, tp->token, TOKMAXLEN) != 0)
  {
    tp = datebsearch(lowtoken, datetktbl, szdatetktbl);
  }
  if (tp == NULL)
  {
    type = UNKNOWN_FIELD;
    *val = 0;
  }
  else
  {
    datecache[field] = tp;
    type = tp->type;
    *val = tp->value;
  }

  return type;
}


/* DecodeTimezoneName()
 * Interpret string as a timezone abbreviation or name.
 * Throw error if the name is not recognized.
 *
 * The return value indicates what kind of zone identifier it is:
 *  TZNAME_FIXED_OFFSET: fixed offset from UTC
 *  TZNAME_DYNTZ: dynamic timezone abbreviation
 *  TZNAME_ZONE: full tzdb zone name
 *
 * For TZNAME_FIXED_OFFSET, *offset receives the UTC offset (in seconds,
 * with ISO sign convention: positive is east of Greenwich).
 * For the other two cases, *tz receives the timezone struct representing
 * the zone name or the abbreviation's underlying zone.
 */
int
DecodeTimezoneName(const char *tzname, int *offset, pg_tz **tz)
{
  char     *lowzone;
  int     dterr,
        type;
  DateTimeErrorExtra extra;

  /*
   * First we look in the timezone abbreviation table (to handle cases like
   * "EST"), and if that fails, we look in the timezone database (to handle
   * cases like "America/New_York").  This matches the order in which
   * timestamp input checks the cases; it's important because the timezone
   * database unwisely uses a few zone names that are identical to offset
   * abbreviations.
   */

  /* DecodeTimezoneAbbrev requires lowercase input */
  lowzone = downcase_truncate_identifier(tzname,
                       strlen(tzname),
                       false);

  dterr = DecodeTimezoneAbbrev(0, lowzone, &type, offset, tz, &extra);
  if (dterr)
    DateTimeParseError(dterr, &extra, NULL, NULL, NULL);

  if (type == TZ || type == DTZ)
  {
    /* fixed-offset abbreviation, return the offset */
    return TZNAME_FIXED_OFFSET;
  }
  else if (type == DYNTZ)
  {
    /* dynamic-offset abbreviation, return its referenced timezone */
    return TZNAME_DYNTZ;
  }
  else
  {
    /* try it as a full zone name */
    *tz = pg_tzset(tzname);
    if (*tz == NULL)
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
           errmsg("time zone \"%s\" not recognized", tzname)));
    return TZNAME_ZONE;
  }
}

/* DecodeTimezoneNameToTz()
 * Interpret string as a timezone abbreviation or name.
 * Throw error if the name is not recognized.
 *
 * This is a simple wrapper for DecodeTimezoneName that produces a pg_tz *
 * result in all cases.
 */
pg_tz *
DecodeTimezoneNameToTz(const char *tzname)
{
  pg_tz    *result;
  int     offset;

  if (DecodeTimezoneName(tzname, &offset, &result) == TZNAME_FIXED_OFFSET)
  {
    /* fixed-offset abbreviation, get a pg_tz descriptor for that */
    result = pg_tzset_offset(-offset);  /* flip to POSIX sign convention */
  }
  return result;
}

/* DecodeTimezoneAbbrevPrefix()
 * Interpret prefix of string as a timezone abbreviation, if possible.
 *
 * This has roughly the same functionality as DecodeTimezoneAbbrev(),
 * but the API is adapted to the needs of formatting.c.  Notably,
 * we will match the longest possible prefix of the given string
 * rather than insisting on a complete match, and downcasing is applied
 * here rather than in the caller.
 *
 * Returns the length of the timezone abbreviation, or -1 if not recognized.
 * On success, sets *offset to the GMT offset for the abbreviation if it
 * is a fixed-offset abbreviation, or sets *tz to the pg_tz struct for
 * a dynamic abbreviation.
 */
int
DecodeTimezoneAbbrevPrefix(const char *str, int *offset, pg_tz **tz)
{
  char    lowtoken[TOKMAXLEN + 1];
  int     len;

  *offset = 0;        /* avoid uninitialized vars on failure */
  *tz = NULL;

  /* Downcase as much of the string as we could need */
  for (len = 0; len < TOKMAXLEN; len++)
  {
    if (*str == '\0' || !isalpha((unsigned char) *str))
      break;
    lowtoken[len] = pg_tolower((unsigned char) *str++);
  }
  lowtoken[len] = '\0';

  /*
   * We could avoid doing repeated binary searches if we cared to duplicate
   * datebsearch here, but it's not clear that such an optimization would be
   * worth the trouble.  In common cases there's probably not anything after
   * the zone abbrev anyway.  So just search with successively truncated
   * strings.
   */
  while (len > 0)
  {
    bool    isfixed;
    int     isdst;
    const datetkn *tp;

    /* See if the current session_timezone recognizes it. */
    if (session_timezone &&
      TimeZoneAbbrevIsKnown(lowtoken, session_timezone,
                  &isfixed, offset, &isdst))
    {
      if (isfixed)
      {
        /* flip sign to agree with the convention in zoneabbrevtbl */
        *offset = -(*offset);
      }
      else
      {
        /* Caller must resolve the abbrev's current meaning */
        *tz = session_timezone;
      }
      return len;
    }

    /* Known in zoneabbrevtbl? */
    if (zoneabbrevtbl)
      tp = datebsearch(lowtoken, zoneabbrevtbl->abbrevs,
               zoneabbrevtbl->numabbrevs);
    else
      tp = NULL;
    if (tp != NULL)
    {
      if (tp->type == DYNTZ)
      {
        DateTimeErrorExtra extra;
        pg_tz    *tzp = FetchDynamicTimeZone(zoneabbrevtbl, tp,
                             &extra);

        if (tzp != NULL)
        {
          /* Caller must resolve the abbrev's current meaning */
          *tz = tzp;
          return len;
        }
      }
      else
      {
        /* Fixed-offset zone abbrev, so it's easy */
        *offset = tp->value;
        return len;
      }
    }

    /* Nope, try the next shorter string. */
    lowtoken[--len] = '\0';
  }

  /* Did not find a match */
  return -1;
}


/* ClearPgItmIn
 *
 * Zero out a pg_itm_in
 */
static inline void
ClearPgItmIn(struct pg_itm_in *itm_in)
{
  itm_in->tm_usec = 0;
  itm_in->tm_mday = 0;
  itm_in->tm_mon = 0;
  itm_in->tm_year = 0;
}


/* DecodeInterval()
 * Interpret previously parsed fields for general time interval.
 * Returns 0 if successful, DTERR code if bogus input detected.
 * dtype and itm_in are output parameters.
 *
 * Allow "date" field DTK_DATE since this could be just
 *  an unsigned floating point number. - thomas 1997-11-16
 *
 * Allow ISO-style time span, with implicit units on number of days
 *  preceding an hh:mm:ss field. - thomas 1998-04-30
 *
 * itm_in remains undefined for infinite interval values for which dtype alone
 * suffices.
 */
int
DecodeInterval(char **field, int *ftype, int nf, int range,
         int *dtype, struct pg_itm_in *itm_in)
{
  bool    force_negative = false;
  bool    is_before = false;
  bool    parsing_unit_val = false;
  char     *cp;
  int     fmask = 0,
        tmask,
        type,
        uval;
  int     i;
  int     dterr;
  int64   val;
  double    fval;

  *dtype = DTK_DELTA;
  type = IGNORE_DTF;
  ClearPgItmIn(itm_in);

  /*----------
   * The SQL standard defines the interval literal
   *   '-1 1:00:00'
   * to mean "negative 1 days and negative 1 hours", while Postgres
   * traditionally treats this as meaning "negative 1 days and positive
   * 1 hours".  In SQL_STANDARD intervalstyle, we apply the leading sign
   * to all fields if there are no other explicit signs.
   *
   * We leave the signs alone if there are additional explicit signs.
   * This protects us against misinterpreting postgres-style dump output,
   * since the postgres-style output code has always put an explicit sign on
   * all fields following a negative field.  But note that SQL-spec output
   * is ambiguous and can be misinterpreted on load!  (So it's best practice
   * to dump in postgres style, not SQL style.)
   *----------
   */
  if (IntervalStyle == INTSTYLE_SQL_STANDARD && nf > 0 && *field[0] == '-')
  {
    force_negative = true;
    /* Check for additional explicit signs */
    for (i = 1; i < nf; i++)
    {
      if (*field[i] == '-' || *field[i] == '+')
      {
        force_negative = false;
        break;
      }
    }
  }

  /* read through list backwards to pick up units before values */
  for (i = nf - 1; i >= 0; i--)
  {
    switch (ftype[i])
    {
      case DTK_TIME:
        dterr = DecodeTimeForInterval(field[i], fmask, range,
                        &tmask, itm_in);
        if (dterr)
          return dterr;
        if (force_negative &&
          itm_in->tm_usec > 0)
          itm_in->tm_usec = -itm_in->tm_usec;
        type = DTK_DAY;
        parsing_unit_val = false;
        break;

      case DTK_TZ:

        /*
         * Timezone means a token with a leading sign character and at
         * least one digit; there could be ':', '.', '-' embedded in
         * it as well.
         */
        Assert(*field[i] == '-' || *field[i] == '+');

        /*
         * Check for signed hh:mm or hh:mm:ss.  If so, process exactly
         * like DTK_TIME case above, plus handling the sign.
         */
        if (strchr(field[i] + 1, ':') != NULL &&
          DecodeTimeForInterval(field[i] + 1, fmask, range,
                      &tmask, itm_in) == 0)
        {
          if (*field[i] == '-')
          {
            /* flip the sign on time field */
            if (itm_in->tm_usec == PG_INT64_MIN)
              return DTERR_FIELD_OVERFLOW;
            itm_in->tm_usec = -itm_in->tm_usec;
          }

          if (force_negative &&
            itm_in->tm_usec > 0)
            itm_in->tm_usec = -itm_in->tm_usec;

          /*
           * Set the next type to be a day, if units are not
           * specified. This handles the case of '1 +02:03' since we
           * are reading right to left.
           */
          type = DTK_DAY;
          parsing_unit_val = false;
          break;
        }

        /*
         * Otherwise, fall through to DTK_NUMBER case, which can
         * handle signed float numbers and signed year-month values.
         */

        /* FALLTHROUGH */

      case DTK_DATE:
      case DTK_NUMBER:
        if (type == IGNORE_DTF)
        {
          /* use typmod to decide what rightmost field is */
          switch (range)
          {
            case INTERVAL_MASK(YEAR):
              type = DTK_YEAR;
              break;
            case INTERVAL_MASK(MONTH):
            case INTERVAL_MASK(YEAR) | INTERVAL_MASK(MONTH):
              type = DTK_MONTH;
              break;
            case INTERVAL_MASK(DAY):
              type = DTK_DAY;
              break;
            case INTERVAL_MASK(HOUR):
            case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR):
              type = DTK_HOUR;
              break;
            case INTERVAL_MASK(MINUTE):
            case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
            case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
              type = DTK_MINUTE;
              break;
            case INTERVAL_MASK(SECOND):
            case INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
              type = DTK_SECOND;
              break;
            default:
              type = DTK_SECOND;
              break;
          }
        }

        errno = 0;
        val = strtoi64(field[i], &cp, 10);
        if (errno == ERANGE)
          return DTERR_FIELD_OVERFLOW;

        if (*cp == '-')
        {
          /* SQL "years-months" syntax */
          int     val2;

          val2 = strtoint(cp + 1, &cp, 10);
          if (errno == ERANGE || val2 < 0 || val2 >= MONTHS_PER_YEAR)
            return DTERR_FIELD_OVERFLOW;
          if (*cp != '\0')
            return DTERR_BAD_FORMAT;
          type = DTK_MONTH;
          if (*field[i] == '-')
            val2 = -val2;
          if (pg_mul_s64_overflow(val, MONTHS_PER_YEAR, &val))
            return DTERR_FIELD_OVERFLOW;
          if (pg_add_s64_overflow(val, val2, &val))
            return DTERR_FIELD_OVERFLOW;
          fval = 0;
        }
        else if (*cp == '.')
        {
          dterr = ParseFraction(cp, &fval);
          if (dterr)
            return dterr;
          if (*field[i] == '-')
            fval = -fval;
        }
        else if (*cp == '\0')
          fval = 0;
        else
          return DTERR_BAD_FORMAT;

        tmask = 0;    /* DTK_M(type); */

        if (force_negative)
        {
          /* val and fval should be of same sign, but test anyway */
          if (val > 0)
            val = -val;
          if (fval > 0)
            fval = -fval;
        }

        switch (type)
        {
          case DTK_MICROSEC:
            if (!AdjustMicroseconds(val, fval, 1, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(MICROSECOND);
            break;

          case DTK_MILLISEC:
            if (!AdjustMicroseconds(val, fval, 1000, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(MILLISECOND);
            break;

          case DTK_SECOND:
            if (!AdjustMicroseconds(val, fval, USECS_PER_SEC, itm_in))
              return DTERR_FIELD_OVERFLOW;

            /*
             * If any subseconds were specified, consider this
             * microsecond and millisecond input as well.
             */
            if (fval == 0)
              tmask = DTK_M(SECOND);
            else
              tmask = DTK_ALL_SECS_M;
            break;

          case DTK_MINUTE:
            if (!AdjustMicroseconds(val, fval, USECS_PER_MINUTE, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(MINUTE);
            break;

          case DTK_HOUR:
            if (!AdjustMicroseconds(val, fval, USECS_PER_HOUR, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(HOUR);
            type = DTK_DAY; /* set for next field */
            break;

          case DTK_DAY:
            if (!AdjustDays(val, 1, itm_in) ||
              !AdjustFractMicroseconds(fval, USECS_PER_DAY, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(DAY);
            break;

          case DTK_WEEK:
            if (!AdjustDays(val, 7, itm_in) ||
              !AdjustFractDays(fval, 7, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(WEEK);
            break;

          case DTK_MONTH:
            if (!AdjustMonths(val, itm_in) ||
              !AdjustFractDays(fval, DAYS_PER_MONTH, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(MONTH);
            break;

          case DTK_YEAR:
            if (!AdjustYears(val, 1, itm_in) ||
              !AdjustFractYears(fval, 1, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(YEAR);
            break;

          case DTK_DECADE:
            if (!AdjustYears(val, 10, itm_in) ||
              !AdjustFractYears(fval, 10, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(DECADE);
            break;

          case DTK_CENTURY:
            if (!AdjustYears(val, 100, itm_in) ||
              !AdjustFractYears(fval, 100, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(CENTURY);
            break;

          case DTK_MILLENNIUM:
            if (!AdjustYears(val, 1000, itm_in) ||
              !AdjustFractYears(fval, 1000, itm_in))
              return DTERR_FIELD_OVERFLOW;
            tmask = DTK_M(MILLENNIUM);
            break;

          default:
            return DTERR_BAD_FORMAT;
        }
        parsing_unit_val = false;
        break;

      case DTK_STRING:
      case DTK_SPECIAL:
        /* reject consecutive unhandled units */
        if (parsing_unit_val)
          return DTERR_BAD_FORMAT;
        type = DecodeUnits(i, field[i], &uval);
        if (type == UNKNOWN_FIELD)
          type = DecodeSpecial(i, field[i], &uval);
        if (type == IGNORE_DTF)
          continue;

        tmask = 0;    /* DTK_M(type); */
        switch (type)
        {
          case UNITS:
            type = uval;
            parsing_unit_val = true;
            break;

          case AGO:

            /*
             * "ago" is only allowed to appear at the end of the
             * interval.
             */
            if (i != nf - 1)
              return DTERR_BAD_FORMAT;
            is_before = true;
            type = uval;
            break;

          case RESERV:
            tmask = (DTK_DATE_M | DTK_TIME_M);

            /*
             * Only reserved words corresponding to infinite
             * intervals are accepted.
             */
            if (uval != DTK_LATE && uval != DTK_EARLY)
              return DTERR_BAD_FORMAT;

            /*
             * Infinity cannot be followed by anything else. We
             * could allow "ago" to reverse the sign of infinity
             * but using signed infinity is more intuitive.
             */
            if (i != nf - 1)
              return DTERR_BAD_FORMAT;

            *dtype = uval;
            break;

          default:
            return DTERR_BAD_FORMAT;
        }
        break;

      default:
        return DTERR_BAD_FORMAT;
    }

    if (tmask & fmask)
      return DTERR_BAD_FORMAT;
    fmask |= tmask;
  }

  /* ensure that at least one time field has been found */
  if (fmask == 0)
    return DTERR_BAD_FORMAT;

  /* reject if unit appeared and was never handled */
  if (parsing_unit_val)
    return DTERR_BAD_FORMAT;

  /* finally, AGO negates everything */
  if (is_before)
  {
    if (itm_in->tm_usec == PG_INT64_MIN ||
      itm_in->tm_mday == INT_MIN ||
      itm_in->tm_mon == INT_MIN ||
      itm_in->tm_year == INT_MIN)
      return DTERR_FIELD_OVERFLOW;

    itm_in->tm_usec = -itm_in->tm_usec;
    itm_in->tm_mday = -itm_in->tm_mday;
    itm_in->tm_mon = -itm_in->tm_mon;
    itm_in->tm_year = -itm_in->tm_year;
  }

  return 0;
}


/*
 * Helper functions to avoid duplicated code in DecodeISO8601Interval.
 *
 * Parse a decimal value and break it into integer and fractional parts.
 * Set *endptr to end+1 of the parsed substring.
 * Returns 0 or DTERR code.
 */
static int
ParseISO8601Number(char *str, char **endptr, int64 *ipart, double *fpart)
{
  double    val;

  /*
   * Historically this has accepted anything that strtod() would take,
   * notably including "e" notation, so continue doing that.  This is
   * slightly annoying because the precision of double is less than that of
   * int64, so we would lose accuracy for inputs larger than 2^53 or so.
   * However, historically we rejected inputs outside the int32 range,
   * making that concern moot.  What we do now is reject abs(val) above
   * 1.0e15 (a round number a bit less than 2^50), so that any accepted
   * value will have an exact integer part, and thereby a fraction part with
   * abs(*fpart) less than 1.  In the absence of field complaints it doesn't
   * seem worth working harder.
   */
  if (!(isdigit((unsigned char) *str) || *str == '-' || *str == '.'))
    return DTERR_BAD_FORMAT;
  errno = 0;
  val = strtod(str, endptr);
  /* did we not see anything that looks like a double? */
  if (*endptr == str || errno != 0)
    return DTERR_BAD_FORMAT;
  /* watch out for overflow, including infinities; reject NaN too */
  if (isnan(val) || val < -1.0e15 || val > 1.0e15)
    return DTERR_FIELD_OVERFLOW;
  /* be very sure we truncate towards zero (cf dtrunc()) */
  if (val >= 0)
    *ipart = (int64) floor(val);
  else
    *ipart = (int64) -floor(-val);
  *fpart = val - *ipart;
  /* Callers expect this to hold */
  Assert(*fpart > -1.0 && *fpart < 1.0);
  return 0;
}

/*
 * Determine number of integral digits in a valid ISO 8601 number field
 * (we should ignore sign and any fraction part)
 */
static int
ISO8601IntegerWidth(char *fieldstart)
{
  /* We might have had a leading '-' */
  if (*fieldstart == '-')
    fieldstart++;
  return strspn(fieldstart, "0123456789");
}


/* DecodeISO8601Interval()
 *  Decode an ISO 8601 time interval of the "format with designators"
 *  (section 4.4.3.2) or "alternative format" (section 4.4.3.3)
 *  Examples:  P1D  for 1 day
 *         PT1H for 1 hour
 *         P2Y6M7DT1H30M for 2 years, 6 months, 7 days 1 hour 30 min
 *         P0002-06-07T01:30:00 the same value in alternative format
 *
 * Returns 0 if successful, DTERR code if bogus input detected.
 * Note: error code should be DTERR_BAD_FORMAT if input doesn't look like
 * ISO8601, otherwise this could cause unexpected error messages.
 * dtype and itm_in are output parameters.
 *
 *  A couple exceptions from the spec:
 *   - a week field ('W') may coexist with other units
 *   - allows decimals in fields other than the least significant unit.
 */
int
DecodeISO8601Interval(char *str,
            int *dtype, struct pg_itm_in *itm_in)
{
  bool    datepart = true;
  bool    havefield = false;

  *dtype = DTK_DELTA;
  ClearPgItmIn(itm_in);

  if (strlen(str) < 2 || str[0] != 'P')
    return DTERR_BAD_FORMAT;

  str++;
  while (*str)
  {
    char     *fieldstart;
    int64   val;
    double    fval;
    char    unit;
    int     dterr;

    if (*str == 'T')   /* T indicates the beginning of the time part */
    {
      datepart = false;
      havefield = false;
      str++;
      continue;
    }

    fieldstart = str;
    dterr = ParseISO8601Number(str, &str, &val, &fval);
    if (dterr)
      return dterr;

    /*
     * Note: we could step off the end of the string here.  Code below
     * *must* exit the loop if unit == '\0'.
     */
    unit = *str++;

    if (datepart)
    {
      switch (unit)   /* before T: Y M W D */
      {
        case 'Y':
          if (!AdjustYears(val, 1, itm_in) ||
            !AdjustFractYears(fval, 1, itm_in))
            return DTERR_FIELD_OVERFLOW;
          break;
        case 'M':
          if (!AdjustMonths(val, itm_in) ||
            !AdjustFractDays(fval, DAYS_PER_MONTH, itm_in))
            return DTERR_FIELD_OVERFLOW;
          break;
        case 'W':
          if (!AdjustDays(val, 7, itm_in) ||
            !AdjustFractDays(fval, 7, itm_in))
            return DTERR_FIELD_OVERFLOW;
          break;
        case 'D':
          if (!AdjustDays(val, 1, itm_in) ||
            !AdjustFractMicroseconds(fval, USECS_PER_DAY, itm_in))
            return DTERR_FIELD_OVERFLOW;
          break;
        case 'T':   /* ISO 8601 4.4.3.3 Alternative Format / Basic */
        case '\0':
          if (ISO8601IntegerWidth(fieldstart) == 8 && !havefield)
          {
            if (!AdjustYears(val / 10000, 1, itm_in) ||
              !AdjustMonths((val / 100) % 100, itm_in) ||
              !AdjustDays(val % 100, 1, itm_in) ||
              !AdjustFractMicroseconds(fval, USECS_PER_DAY, itm_in))
              return DTERR_FIELD_OVERFLOW;
            if (unit == '\0')
              return 0;
            datepart = false;
            havefield = false;
            continue;
          }
          /* Else fall through to extended alternative format */
          /* FALLTHROUGH */
        case '-':   /* ISO 8601 4.4.3.3 Alternative Format,
                 * Extended */
          if (havefield)
            return DTERR_BAD_FORMAT;

          if (!AdjustYears(val, 1, itm_in) ||
            !AdjustFractYears(fval, 1, itm_in))
            return DTERR_FIELD_OVERFLOW;
          if (unit == '\0')
            return 0;
          if (unit == 'T')
          {
            datepart = false;
            havefield = false;
            continue;
          }

          dterr = ParseISO8601Number(str, &str, &val, &fval);
          if (dterr)
            return dterr;
          if (!AdjustMonths(val, itm_in) ||
            !AdjustFractDays(fval, DAYS_PER_MONTH, itm_in))
            return DTERR_FIELD_OVERFLOW;
          if (*str == '\0')
            return 0;
          if (*str == 'T')
          {
            datepart = false;
            havefield = false;
            continue;
          }
          if (*str != '-')
            return DTERR_BAD_FORMAT;
          str++;

          dterr = ParseISO8601Number(str, &str, &val, &fval);
          if (dterr)
            return dterr;
          if (!AdjustDays(val, 1, itm_in) ||
            !AdjustFractMicroseconds(fval, USECS_PER_DAY, itm_in))
            return DTERR_FIELD_OVERFLOW;
          if (*str == '\0')
            return 0;
          if (*str == 'T')
          {
            datepart = false;
            havefield = false;
            continue;
          }
          return DTERR_BAD_FORMAT;
        default:
          /* not a valid date unit suffix */
          return DTERR_BAD_FORMAT;
      }
    }
    else
    {
      switch (unit)   /* after T: H M S */
      {
        case 'H':
          if (!AdjustMicroseconds(val, fval, USECS_PER_HOUR, itm_in))
            return DTERR_FIELD_OVERFLOW;
          break;
        case 'M':
          if (!AdjustMicroseconds(val, fval, USECS_PER_MINUTE, itm_in))
            return DTERR_FIELD_OVERFLOW;
          break;
        case 'S':
          if (!AdjustMicroseconds(val, fval, USECS_PER_SEC, itm_in))
            return DTERR_FIELD_OVERFLOW;
          break;
        case '\0':    /* ISO 8601 4.4.3.3 Alternative Format */
          if (ISO8601IntegerWidth(fieldstart) == 6 && !havefield)
          {
            if (!AdjustMicroseconds(val / 10000, 0, USECS_PER_HOUR, itm_in) ||
              !AdjustMicroseconds((val / 100) % 100, 0, USECS_PER_MINUTE, itm_in) ||
              !AdjustMicroseconds(val % 100, 0, USECS_PER_SEC, itm_in) ||
              !AdjustFractMicroseconds(fval, 1, itm_in))
              return DTERR_FIELD_OVERFLOW;
            return 0;
          }
          /* Else fall through to extended alternative format */
          /* FALLTHROUGH */
        case ':':   /* ISO 8601 4.4.3.3 Alternative Format,
                 * Extended */
          if (havefield)
            return DTERR_BAD_FORMAT;

          if (!AdjustMicroseconds(val, fval, USECS_PER_HOUR, itm_in))
            return DTERR_FIELD_OVERFLOW;
          if (unit == '\0')
            return 0;

          dterr = ParseISO8601Number(str, &str, &val, &fval);
          if (dterr)
            return dterr;
          if (!AdjustMicroseconds(val, fval, USECS_PER_MINUTE, itm_in))
            return DTERR_FIELD_OVERFLOW;
          if (*str == '\0')
            return 0;
          if (*str != ':')
            return DTERR_BAD_FORMAT;
          str++;

          dterr = ParseISO8601Number(str, &str, &val, &fval);
          if (dterr)
            return dterr;
          if (!AdjustMicroseconds(val, fval, USECS_PER_SEC, itm_in))
            return DTERR_FIELD_OVERFLOW;
          if (*str == '\0')
            return 0;
          return DTERR_BAD_FORMAT;

        default:
          /* not a valid time unit suffix */
          return DTERR_BAD_FORMAT;
      }
    }

    havefield = true;
  }

  return 0;
}


/* DecodeUnits()
 * Decode text string using lookup table.
 *
 * This routine recognizes keywords associated with time interval units.
 *
 * Given string must be lowercased already.
 *
 * Implement a cache lookup since it is likely that dates
 *  will be related in format.
 */
int
DecodeUnits(int field, const char *lowtoken, int *val)
{
  int     type;
  const datetkn *tp;

  tp = deltacache[field];
  /* use strncmp so that we match truncated tokens */
  if (tp == NULL || strncmp(lowtoken, tp->token, TOKMAXLEN) != 0)
  {
    tp = datebsearch(lowtoken, deltatktbl, szdeltatktbl);
  }
  if (tp == NULL)
  {
    type = UNKNOWN_FIELD;
    *val = 0;
  }
  else
  {
    deltacache[field] = tp;
    type = tp->type;
    *val = tp->value;
  }

  return type;
}                /* DecodeUnits() */

/*
 * Report an error detected by one of the datetime input processing routines.
 *
 * dterr is the error code, and *extra contains any auxiliary info we need
 * for the error report.  extra can be NULL if not needed for the particular
 * dterr value.
 *
 * str is the original input string, and datatype is the name of the datatype
 * we were trying to accept.  (For some DTERR codes, these are not used and
 * can be NULL.)
 *
 * If escontext points to an ErrorSaveContext node, that is filled instead
 * of throwing an error.
 *
 * Note: it might seem useless to distinguish DTERR_INTERVAL_OVERFLOW and
 * DTERR_TZDISP_OVERFLOW from DTERR_FIELD_OVERFLOW, but SQL99 mandates three
 * separate SQLSTATE codes, so ...
 */
void
DateTimeParseError(int dterr, DateTimeErrorExtra *extra,
           const char *str, const char *datatype,
           Node *escontext)
{
  switch (dterr)
  {
    case DTERR_FIELD_OVERFLOW:
      errsave(escontext,
          (errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
           errmsg("date/time field value out of range: \"%s\"",
              str)));
      break;
    case DTERR_MD_FIELD_OVERFLOW:
      /* <nanny>same as above, but add hint about DateStyle</nanny> */
      errsave(escontext,
          (errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
           errmsg("date/time field value out of range: \"%s\"",
              str),
           errhint("Perhaps you need a different \"DateStyle\" setting.")));
      break;
    case DTERR_INTERVAL_OVERFLOW:
      errsave(escontext,
          (errcode(ERRCODE_INTERVAL_FIELD_OVERFLOW),
           errmsg("interval field value out of range: \"%s\"",
              str)));
      break;
    case DTERR_TZDISP_OVERFLOW:
      errsave(escontext,
          (errcode(ERRCODE_INVALID_TIME_ZONE_DISPLACEMENT_VALUE),
           errmsg("time zone displacement out of range: \"%s\"",
              str)));
      break;
    case DTERR_BAD_TIMEZONE:
      errsave(escontext,
          (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
           errmsg("time zone \"%s\" not recognized",
              extra->dtee_timezone)));
      break;
    case DTERR_BAD_ZONE_ABBREV:
      errsave(escontext,
          (errcode(ERRCODE_CONFIG_FILE_ERROR),
           errmsg("time zone \"%s\" not recognized",
              extra->dtee_timezone),
           errdetail("This time zone name appears in the configuration file for time zone abbreviation \"%s\".",
                 extra->dtee_abbrev)));
      break;
    case DTERR_BAD_FORMAT:
    default:
      errsave(escontext,
          (errcode(ERRCODE_INVALID_DATETIME_FORMAT),
           errmsg("invalid input syntax for type %s: \"%s\"",
              datatype, str)));
      break;
  }
}

/* datebsearch()
 * Binary search -- from Knuth (6.2.1) Algorithm B.  Special case like this
 * is WAY faster than the generic bsearch().
 */
static const datetkn *
datebsearch(const char *key, const datetkn *base, int nel)
{
  if (nel > 0)
  {
    const datetkn *last = base + nel - 1,
           *position;
    int     result;

    while (last >= base)
    {
      position = base + ((last - base) >> 1);
      /* precheck the first character for a bit of extra speed */
      result = (int) key[0] - (int) position->token[0];
      if (result == 0)
      {
        /* use strncmp so that we match truncated tokens */
        result = strncmp(key, position->token, TOKMAXLEN);
        if (result == 0)
          return position;
      }
      if (result < 0)
        last = position - 1;
      else
        base = position + 1;
    }
  }
  return NULL;
}

/* EncodeTimezone()
 *    Copies representation of a numeric timezone offset to str.
 *
 * Returns a pointer to the new end of string.  No NUL terminator is put
 * there; callers are responsible for NUL terminating str themselves.
 */
static char *
EncodeTimezone(char *str, int tz, int style)
{
  int     hour,
        min,
        sec;

  sec = abs(tz);
  min = sec / SECS_PER_MINUTE;
  sec -= min * SECS_PER_MINUTE;
  hour = min / MINS_PER_HOUR;
  min -= hour * MINS_PER_HOUR;

  /* TZ is negated compared to sign we wish to display ... */
  *str++ = (tz <= 0 ? '+' : '-');

  if (sec != 0)
  {
    str = pg_ultostr_zeropad(str, hour, 2);
    *str++ = ':';
    str = pg_ultostr_zeropad(str, min, 2);
    *str++ = ':';
    str = pg_ultostr_zeropad(str, sec, 2);
  }
  else if (min != 0 || style == USE_XSD_DATES)
  {
    str = pg_ultostr_zeropad(str, hour, 2);
    *str++ = ':';
    str = pg_ultostr_zeropad(str, min, 2);
  }
  else
    str = pg_ultostr_zeropad(str, hour, 2);
  return str;
}

/* EncodeDateOnly()
 * Encode date as local time.
 */
void
EncodeDateOnly(struct pg_tm *tm, int style, char *str)
{
  Assert(tm->tm_mon >= 1 && tm->tm_mon <= MONTHS_PER_YEAR);

  switch (style)
  {
    case USE_ISO_DATES:
    case USE_XSD_DATES:
      /* compatible with ISO date formats */
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
      *str++ = '-';
      str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
      *str++ = '-';
      str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      break;

    case USE_SQL_DATES:
      /* compatible with Oracle/Ingres date formats */
      if (DateOrder == DATEORDER_DMY)
      {
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
        *str++ = '/';
        str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
      }
      else
      {
        str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
        *str++ = '/';
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      }
      *str++ = '/';
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
      break;

    case USE_GERMAN_DATES:
      /* German-style date format */
      str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      *str++ = '.';
      str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
      *str++ = '.';
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
      break;

    case USE_POSTGRES_DATES:
    default:
      /* traditional date-only style for Postgres */
      if (DateOrder == DATEORDER_DMY)
      {
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
        *str++ = '-';
        str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
      }
      else
      {
        str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
        *str++ = '-';
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      }
      *str++ = '-';
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
      break;
  }

  if (tm->tm_year <= 0)
  {
    memcpy(str, " BC", 3);  /* Don't copy NUL */
    str += 3;
  }
  *str = '\0';
}


/* EncodeTimeOnly()
 * Encode time fields only.
 *
 * tm and fsec are the value to encode, print_tz determines whether to include
 * a time zone (the difference between time and timetz types), tz is the
 * numeric time zone offset, style is the date style, str is where to write the
 * output.
 */
void
EncodeTimeOnly(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, int style, char *str)
{
  str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
  *str++ = ':';
  str = pg_ultostr_zeropad(str, tm->tm_min, 2);
  *str++ = ':';
  str = AppendSeconds(str, tm->tm_sec, fsec, MAX_TIME_PRECISION, true);
  if (print_tz)
    str = EncodeTimezone(str, tz, style);
  *str = '\0';
}


/* EncodeDateTime()
 * Encode date and time interpreted as local time.
 *
 * tm and fsec are the value to encode, print_tz determines whether to include
 * a time zone (the difference between timestamp and timestamptz types), tz is
 * the numeric time zone offset, tzn is the textual time zone, which if
 * specified will be used instead of tz by some styles, style is the date
 * style, str is where to write the output.
 *
 * Supported date styles:
 *  Postgres - day mon hh:mm:ss yyyy tz
 *  SQL - mm/dd/yyyy hh:mm:ss.ss tz
 *  ISO - yyyy-mm-dd hh:mm:ss+/-tz
 *  German - dd.mm.yyyy hh:mm:ss tz
 *  XSD - yyyy-mm-ddThh:mm:ss.ss+/-tz
 */
void
EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char *tzn, int style, char *str)
{
  int     day;

  Assert(tm->tm_mon >= 1 && tm->tm_mon <= MONTHS_PER_YEAR);

  /*
   * Negative tm_isdst means we have no valid time zone translation.
   */
  if (tm->tm_isdst < 0)
    print_tz = false;

  switch (style)
  {
    case USE_ISO_DATES:
    case USE_XSD_DATES:
      /* Compatible with ISO-8601 date formats */
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
      *str++ = '-';
      str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
      *str++ = '-';
      str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      *str++ = (style == USE_ISO_DATES) ? ' ' : 'T';
      str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
      *str++ = ':';
      str = pg_ultostr_zeropad(str, tm->tm_min, 2);
      *str++ = ':';
      str = AppendTimestampSeconds(str, tm, fsec);
      if (print_tz)
        str = EncodeTimezone(str, tz, style);
      break;

    case USE_SQL_DATES:
      /* Compatible with Oracle/Ingres date formats */
      if (DateOrder == DATEORDER_DMY)
      {
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
        *str++ = '/';
        str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
      }
      else
      {
        str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
        *str++ = '/';
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      }
      *str++ = '/';
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
      *str++ = ' ';
      str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
      *str++ = ':';
      str = pg_ultostr_zeropad(str, tm->tm_min, 2);
      *str++ = ':';
      str = AppendTimestampSeconds(str, tm, fsec);

      /*
       * Note: the uses of %.*s in this function would be risky if the
       * timezone names ever contain non-ASCII characters, since we are
       * not being careful to do encoding-aware clipping.  However, all
       * TZ abbreviations in the IANA database are plain ASCII.
       */
      if (print_tz)
      {
        if (tzn)
        {
          sprintf(str, " %.*s", MAXTZLEN, tzn);
          str += strlen(str);
        }
        else
          str = EncodeTimezone(str, tz, style);
      }
      break;

    case USE_GERMAN_DATES:
      /* German variant on European style */
      str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      *str++ = '.';
      str = pg_ultostr_zeropad(str, tm->tm_mon, 2);
      *str++ = '.';
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
      *str++ = ' ';
      str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
      *str++ = ':';
      str = pg_ultostr_zeropad(str, tm->tm_min, 2);
      *str++ = ':';
      str = AppendTimestampSeconds(str, tm, fsec);

      if (print_tz)
      {
        if (tzn)
        {
          sprintf(str, " %.*s", MAXTZLEN, tzn);
          str += strlen(str);
        }
        else
          str = EncodeTimezone(str, tz, style);
      }
      break;

    case USE_POSTGRES_DATES:
    default:
      /* Backward-compatible with traditional Postgres abstime dates */
      day = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
      tm->tm_wday = j2day(day);
      memcpy(str, days[tm->tm_wday], 3);
      str += 3;
      *str++ = ' ';
      if (DateOrder == DATEORDER_DMY)
      {
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
        *str++ = ' ';
        memcpy(str, months[tm->tm_mon - 1], 3);
        str += 3;
      }
      else
      {
        memcpy(str, months[tm->tm_mon - 1], 3);
        str += 3;
        *str++ = ' ';
        str = pg_ultostr_zeropad(str, tm->tm_mday, 2);
      }
      *str++ = ' ';
      str = pg_ultostr_zeropad(str, tm->tm_hour, 2);
      *str++ = ':';
      str = pg_ultostr_zeropad(str, tm->tm_min, 2);
      *str++ = ':';
      str = AppendTimestampSeconds(str, tm, fsec);
      *str++ = ' ';
      str = pg_ultostr_zeropad(str,
                   (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);

      if (print_tz)
      {
        if (tzn)
        {
          sprintf(str, " %.*s", MAXTZLEN, tzn);
          str += strlen(str);
        }
        else
        {
          /*
           * We have a time zone, but no string version. Use the
           * numeric form, but be sure to include a leading space to
           * avoid formatting something which would be rejected by
           * the date/time parser later. - thomas 2001-10-19
           */
          *str++ = ' ';
          str = EncodeTimezone(str, tz, style);
        }
      }
      break;
  }

  if (tm->tm_year <= 0)
  {
    memcpy(str, " BC", 3);  /* Don't copy NUL */
    str += 3;
  }
  *str = '\0';
}


/*
 * Helper functions to avoid duplicated code in EncodeInterval.
 */

/* Append an ISO-8601-style interval field, but only if value isn't zero */
static char *
AddISO8601IntPart(char *cp, int64 value, char units)
{
  if (value == 0)
    return cp;
  sprintf(cp, "%" PRId64 "%c", value, units);
  return cp + strlen(cp);
}

/* Append a postgres-style interval field, but only if value isn't zero */
static char *
AddPostgresIntPart(char *cp, int64 value, const char *units,
           bool *is_zero, bool *is_before)
{
  if (value == 0)
    return cp;
  sprintf(cp, "%s%s%" PRId64 " %s%s",
      (!*is_zero) ? " " : "",
      (*is_before && value > 0) ? "+" : "",
      value,
      units,
      (value != 1) ? "s" : "");

  /*
   * Each nonzero field sets is_before for (only) the next one.  This is a
   * tad bizarre but it's how it worked before...
   */
  *is_before = (value < 0);
  *is_zero = false;
  return cp + strlen(cp);
}

/* Append a verbose-style interval field, but only if value isn't zero */
static char *
AddVerboseIntPart(char *cp, int64 value, const char *units,
          bool *is_zero, bool *is_before)
{
  if (value == 0)
    return cp;
  /* first nonzero value sets is_before */
  if (*is_zero)
  {
    *is_before = (value < 0);
    value = i64abs(value);
  }
  else if (*is_before)
    value = -value;
  sprintf(cp, " %" PRId64 " %s%s", value, units, (value == 1) ? "" : "s");
  *is_zero = false;
  return cp + strlen(cp);
}


/* EncodeInterval()
 * Interpret time structure as a delta time and convert to string.
 *
 * Support "traditional Postgres" and ISO-8601 styles.
 * Actually, afaik ISO does not address time interval formatting,
 *  but this looks similar to the spec for absolute date/time.
 * - thomas 1998-04-30
 *
 * Actually, afaik, ISO 8601 does specify formats for "time
 * intervals...[of the]...format with time-unit designators", which
 * are pretty ugly.  The format looks something like
 *     P1Y1M1DT1H1M1.12345S
 * but useful for exchanging data with computers instead of humans.
 * - ron 2003-07-14
 *
 * And ISO's SQL 2008 standard specifies standards for
 * "year-month literal"s (that look like '2-3') and
 * "day-time literal"s (that look like ('4 5:6:7')
 */
void
EncodeInterval(struct pg_itm *itm, int style, char *str)
{
  char     *cp = str;
  int     year = itm->tm_year;
  int     mon = itm->tm_mon;
  int64   mday = itm->tm_mday;  /* tm_mday could be INT_MIN */
  int64   hour = itm->tm_hour;
  int     min = itm->tm_min;
  int     sec = itm->tm_sec;
  int     fsec = itm->tm_usec;
  bool    is_before = false;
  bool    is_zero = true;

  /*
   * The sign of year and month are guaranteed to match, since they are
   * stored internally as "month". But we'll need to check for is_before and
   * is_zero when determining the signs of day and hour/minute/seconds
   * fields.
   */
  switch (style)
  {
      /* SQL Standard interval format */
    case INTSTYLE_SQL_STANDARD:
      {
        bool    has_negative = year < 0 || mon < 0 ||
          mday < 0 || hour < 0 ||
          min < 0 || sec < 0 || fsec < 0;
        bool    has_positive = year > 0 || mon > 0 ||
          mday > 0 || hour > 0 ||
          min > 0 || sec > 0 || fsec > 0;
        bool    has_year_month = year != 0 || mon != 0;
        bool    has_day_time = mday != 0 || hour != 0 ||
          min != 0 || sec != 0 || fsec != 0;
        bool    has_day = mday != 0;
        bool    sql_standard_value = !(has_negative && has_positive) &&
          !(has_year_month && has_day_time);

        /*
         * SQL Standard wants only 1 "<sign>" preceding the whole
         * interval ... but can't do that if mixed signs.
         */
        if (has_negative && sql_standard_value)
        {
          *cp++ = '-';
          year = -year;
          mon = -mon;
          mday = -mday;
          hour = -hour;
          min = -min;
          sec = -sec;
          fsec = -fsec;
        }

        if (!has_negative && !has_positive)
        {
          sprintf(cp, "0");
        }
        else if (!sql_standard_value)
        {
          /*
           * For non sql-standard interval values, force outputting
           * the signs to avoid ambiguities with intervals with
           * mixed sign components.
           */
          char    year_sign = (year < 0 || mon < 0) ? '-' : '+';
          char    day_sign = (mday < 0) ? '-' : '+';
          char    sec_sign = (hour < 0 || min < 0 ||
                      sec < 0 || fsec < 0) ? '-' : '+';

          sprintf(cp, "%c%d-%d %c%" PRId64 " %c%" PRId64 ":%02d:",
              year_sign, abs(year), abs(mon),
              day_sign, i64abs(mday),
              sec_sign, i64abs(hour), abs(min));
          cp += strlen(cp);
          cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
          *cp = '\0';
        }
        else if (has_year_month)
        {
          sprintf(cp, "%d-%d", year, mon);
        }
        else if (has_day)
        {
          sprintf(cp, "%" PRId64 " %" PRId64 ":%02d:",
              mday, hour, min);
          cp += strlen(cp);
          cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
          *cp = '\0';
        }
        else
        {
          sprintf(cp, "%" PRId64 ":%02d:", hour, min);
          cp += strlen(cp);
          cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
          *cp = '\0';
        }
      }
      break;

      /* ISO 8601 "time-intervals by duration only" */
    case INTSTYLE_ISO_8601:
      /* special-case zero to avoid printing nothing */
      if (year == 0 && mon == 0 && mday == 0 &&
        hour == 0 && min == 0 && sec == 0 && fsec == 0)
      {
        sprintf(cp, "PT0S");
        break;
      }
      *cp++ = 'P';
      cp = AddISO8601IntPart(cp, year, 'Y');
      cp = AddISO8601IntPart(cp, mon, 'M');
      cp = AddISO8601IntPart(cp, mday, 'D');
      if (hour != 0 || min != 0 || sec != 0 || fsec != 0)
        *cp++ = 'T';
      cp = AddISO8601IntPart(cp, hour, 'H');
      cp = AddISO8601IntPart(cp, min, 'M');
      if (sec != 0 || fsec != 0)
      {
        if (sec < 0 || fsec < 0)
          *cp++ = '-';
        cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, false);
        *cp++ = 'S';
        *cp++ = '\0';
      }
      break;

      /* Compatible with postgresql < 8.4 when DateStyle = 'iso' */
    case INTSTYLE_POSTGRES:
      cp = AddPostgresIntPart(cp, year, "year", &is_zero, &is_before);

      /*
       * Ideally we should spell out "month" like we do for "year" and
       * "day".  However, for backward compatibility, we can't easily
       * fix this.  bjm 2011-05-24
       */
      cp = AddPostgresIntPart(cp, mon, "mon", &is_zero, &is_before);
      cp = AddPostgresIntPart(cp, mday, "day", &is_zero, &is_before);
      if (is_zero || hour != 0 || min != 0 || sec != 0 || fsec != 0)
      {
        bool    minus = (hour < 0 || min < 0 || sec < 0 || fsec < 0);

        sprintf(cp, "%s%s%02" PRId64 ":%02d:",
            is_zero ? "" : " ",
            (minus ? "-" : (is_before ? "+" : "")),
            i64abs(hour), abs(min));
        cp += strlen(cp);
        cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
        *cp = '\0';
      }
      break;

      /* Compatible with postgresql < 8.4 when DateStyle != 'iso' */
    case INTSTYLE_POSTGRES_VERBOSE:
    default:
      strcpy(cp, "@");
      cp++;
      cp = AddVerboseIntPart(cp, year, "year", &is_zero, &is_before);
      cp = AddVerboseIntPart(cp, mon, "mon", &is_zero, &is_before);
      cp = AddVerboseIntPart(cp, mday, "day", &is_zero, &is_before);
      cp = AddVerboseIntPart(cp, hour, "hour", &is_zero, &is_before);
      cp = AddVerboseIntPart(cp, min, "min", &is_zero, &is_before);
      if (sec != 0 || fsec != 0)
      {
        *cp++ = ' ';
        if (sec < 0 || (sec == 0 && fsec < 0))
        {
          if (is_zero)
            is_before = true;
          else if (!is_before)
            *cp++ = '-';
        }
        else if (is_before)
          *cp++ = '-';
        cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, false);
        /* We output "ago", not negatives, so use abs(). */
        sprintf(cp, " sec%s",
            (abs(sec) != 1 || fsec != 0) ? "s" : "");
        is_zero = false;
      }
      /* identically zero? then put in a unitless zero... */
      if (is_zero)
        strcat(cp, " 0");
      if (is_before)
        strcat(cp, " ago");
      break;
  }
}


/*
 * We've been burnt by stupid errors in the ordering of the datetkn tables
 * once too often.  Arrange to check them during postmaster start.
 */
static bool
CheckDateTokenTable(const char *tablename, const datetkn *base, int nel)
{
  bool    ok = true;
  int     i;

  for (i = 0; i < nel; i++)
  {
    /* check for token strings that don't fit */
    if (strlen(base[i].token) > TOKMAXLEN)
    {
      /* %.*s is safe since all our tokens are ASCII */
      elog(LOG, "token too long in %s table: \"%.*s\"",
         tablename,
         TOKMAXLEN + 1, base[i].token);
      ok = false;
      break;       /* don't risk applying strcmp */
    }
    /* check for out of order */
    if (i > 0 &&
      strcmp(base[i - 1].token, base[i].token) >= 0)
    {
      elog(LOG, "ordering error in %s table: \"%s\" >= \"%s\"",
         tablename,
         base[i - 1].token,
         base[i].token);
      ok = false;
    }
  }
  return ok;
}

bool
CheckDateTokenTables(void)
{
  bool    ok = true;

  Assert(UNIX_EPOCH_JDATE == date2j(1970, 1, 1));
  Assert(POSTGRES_EPOCH_JDATE == date2j(2000, 1, 1));

  ok &= CheckDateTokenTable("datetktbl", datetktbl, szdatetktbl);
  ok &= CheckDateTokenTable("deltatktbl", deltatktbl, szdeltatktbl);
  return ok;
}

/*
 * Common code for temporal prosupport functions: simplify, if possible,
 * a call to a temporal type's length-coercion function.
 *
 * Types time, timetz, timestamp and timestamptz each have a range of allowed
 * precisions.  An unspecified precision is rigorously equivalent to the
 * highest specifiable precision.  We can replace the function call with a
 * no-op RelabelType if it is coercing to the same or higher precision as the
 * input is known to have.
 *
 * The input Node is always a FuncExpr, but to reduce the #include footprint
 * of datetime.h, we declare it as Node *.
 *
 * Note: timestamp_scale throws an error when the typmod is out of range, but
 * we can't get there from a cast: our typmodin will have caught it already.
 */
Node *
TemporalSimplify(int32 max_precis, Node *node)
{
  FuncExpr   *expr = castNode(FuncExpr, node);
  Node     *ret = NULL;
  Node     *typmod;

  Assert(list_length(expr->args) >= 2);

  typmod = (Node *) lsecond(expr->args);

  if (IsA(typmod, Const) && !((Const *) typmod)->constisnull)
  {
    Node     *source = (Node *) linitial(expr->args);
    int32   old_precis = exprTypmod(source);
    int32   new_precis = DatumGetInt32(((Const *) typmod)->constvalue);

    if (new_precis < 0 || new_precis == max_precis ||
      (old_precis >= 0 && new_precis >= old_precis))
      ret = relabel_to_typmod(source, new_precis);
  }

  return ret;
}

/*
 * This function gets called during timezone config file load or reload
 * to create the final array of timezone tokens.  The argument array
 * is already sorted in name order.
 *
 * The result is a TimeZoneAbbrevTable (which must be a single guc_malloc'd
 * chunk) or NULL on alloc failure.  No other error conditions are defined.
 */
TimeZoneAbbrevTable *
ConvertTimeZoneAbbrevs(struct tzEntry *abbrevs, int n)
{
  TimeZoneAbbrevTable *tbl;
  Size    tbl_size;
  int     i;

  /* Space for fixed fields and datetkn array */
  tbl_size = offsetof(TimeZoneAbbrevTable, abbrevs) +
    n * sizeof(datetkn);
  tbl_size = MAXALIGN(tbl_size);
  /* Count up space for dynamic abbreviations */
  for (i = 0; i < n; i++)
  {
    struct tzEntry *abbr = abbrevs + i;

    if (abbr->zone != NULL)
    {
      Size    dsize;

      dsize = offsetof(DynamicZoneAbbrev, zone) +
        strlen(abbr->zone) + 1;
      tbl_size += MAXALIGN(dsize);
    }
  }

  /* Alloc the result ... */
  tbl = guc_malloc(LOG, tbl_size);
  if (!tbl)
    return NULL;

  /* ... and fill it in */
  tbl->tblsize = tbl_size;
  tbl->numabbrevs = n;
  /* in this loop, tbl_size reprises the space calculation above */
  tbl_size = offsetof(TimeZoneAbbrevTable, abbrevs) +
    n * sizeof(datetkn);
  tbl_size = MAXALIGN(tbl_size);
  for (i = 0; i < n; i++)
  {
    struct tzEntry *abbr = abbrevs + i;
    datetkn    *dtoken = tbl->abbrevs + i;

    /* use strlcpy to truncate name if necessary */
    strlcpy(dtoken->token, abbr->abbrev, TOKMAXLEN + 1);
    if (abbr->zone != NULL)
    {
      /* Allocate a DynamicZoneAbbrev for this abbreviation */
      DynamicZoneAbbrev *dtza;
      Size    dsize;

      dtza = (DynamicZoneAbbrev *) ((char *) tbl + tbl_size);
      dtza->tz = NULL;
      strcpy(dtza->zone, abbr->zone);

      dtoken->type = DYNTZ;
      /* value is offset from table start to DynamicZoneAbbrev */
      dtoken->value = (int32) tbl_size;

      dsize = offsetof(DynamicZoneAbbrev, zone) +
        strlen(abbr->zone) + 1;
      tbl_size += MAXALIGN(dsize);
    }
    else
    {
      dtoken->type = abbr->is_dst ? DTZ : TZ;
      dtoken->value = abbr->offset;
    }
  }

  /* Assert the two loops above agreed on size calculations */
  Assert(tbl->tblsize == tbl_size);

  /* Check the ordering, if testing */
  Assert(CheckDateTokenTable("timezone abbreviations", tbl->abbrevs, n));

  return tbl;
}

/*
 * Install a TimeZoneAbbrevTable as the active table.
 *
 * Caller is responsible that the passed table doesn't go away while in use.
 */
void
InstallTimeZoneAbbrevs(TimeZoneAbbrevTable *tbl)
{
  zoneabbrevtbl = tbl;
  /* reset tzabbrevcache, which may contain results from old table */
  memset(tzabbrevcache, 0, sizeof(tzabbrevcache));
}

/*
 * Helper subroutine to locate pg_tz timezone for a dynamic abbreviation.
 *
 * On failure, returns NULL and fills *extra for a DTERR_BAD_ZONE_ABBREV error.
 */
static pg_tz *
FetchDynamicTimeZone(TimeZoneAbbrevTable *tbl, const datetkn *tp,
           DateTimeErrorExtra *extra)
{
  DynamicZoneAbbrev *dtza;

  /* Just some sanity checks to prevent indexing off into nowhere */
  Assert(tp->type == DYNTZ);
  Assert(tp->value > 0 && tp->value < tbl->tblsize);

  dtza = (DynamicZoneAbbrev *) ((char *) tbl + tp->value);

  /* Look up the underlying zone if we haven't already */
  if (dtza->tz == NULL)
  {
    dtza->tz = pg_tzset(dtza->zone);
    if (dtza->tz == NULL)
    {
      /* Ooops, bogus zone name in config file entry */
      extra->dtee_timezone = dtza->zone;
      extra->dtee_abbrev = tp->token;
    }
  }
  return dtza->tz;
}


/*
 * This set-returning function reads all the time zone abbreviations
 * defined by the IANA data for the current timezone setting,
 * and returns a set of (abbrev, utc_offset, is_dst).
 */
Datum
pg_timezone_abbrevs_zone(PG_FUNCTION_ARGS)
{
  FuncCallContext *funcctx;
  int      *pindex;
  Datum   result;
  HeapTuple tuple;
  Datum   values[3];
  bool    nulls[3] = {0};
  TimestampTz now = GetCurrentTransactionStartTimestamp();
  pg_time_t t = timestamptz_to_time_t(now);
  const char *abbrev;
  long int  gmtoff;
  int     isdst;
  struct pg_itm_in itm_in;
  Interval   *resInterval;

  /* stuff done only on the first call of the function */
  if (SRF_IS_FIRSTCALL())
  {
    TupleDesc tupdesc;
    MemoryContext oldcontext;

    /* create a function context for cross-call persistence */
    funcctx = SRF_FIRSTCALL_INIT();

    /*
     * switch to memory context appropriate for multiple function calls
     */
    oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

    /* allocate memory for user context */
    pindex = (int *) palloc(sizeof(int));
    *pindex = 0;
    funcctx->user_fctx = pindex;

    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
      elog(ERROR, "return type must be a row type");
    funcctx->tuple_desc = tupdesc;

    MemoryContextSwitchTo(oldcontext);
  }

  /* stuff done on every call of the function */
  funcctx = SRF_PERCALL_SETUP();
  pindex = (int *) funcctx->user_fctx;

  while ((abbrev = pg_get_next_timezone_abbrev(pindex,
                         session_timezone)) != NULL)
  {
    /* Ignore abbreviations that aren't all-alphabetic */
    if (strspn(abbrev, "ABCDEFGHIJKLMNOPQRSTUVWXYZ") != strlen(abbrev))
      continue;

    /* Determine the current meaning of the abbrev */
    if (!pg_interpret_timezone_abbrev(abbrev,
                      &t,
                      &gmtoff,
                      &isdst,
                      session_timezone))
      continue;     /* hm, not actually used in this zone? */

    values[0] = CStringGetTextDatum(abbrev);

    /* Convert offset (in seconds) to an interval; can't overflow */
    MemSet(&itm_in, 0, sizeof(struct pg_itm_in));
    itm_in.tm_usec = (int64) gmtoff * USECS_PER_SEC;
    resInterval = (Interval *) palloc(sizeof(Interval));
    (void) itmin2interval(&itm_in, resInterval);
    values[1] = IntervalPGetDatum(resInterval);

    values[2] = BoolGetDatum(isdst);

    tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
    result = HeapTupleGetDatum(tuple);

    SRF_RETURN_NEXT(funcctx, result);
  }

  SRF_RETURN_DONE(funcctx);
}

/*
 * This set-returning function reads all the time zone abbreviations
 * defined by the timezone_abbreviations setting,
 * and returns a set of (abbrev, utc_offset, is_dst).
 */
Datum
pg_timezone_abbrevs_abbrevs(PG_FUNCTION_ARGS)
{
  FuncCallContext *funcctx;
  int      *pindex;
  Datum   result;
  HeapTuple tuple;
  Datum   values[3];
  bool    nulls[3] = {0};
  const datetkn *tp;
  char    buffer[TOKMAXLEN + 1];
  int     gmtoffset;
  bool    is_dst;
  unsigned char *p;
  struct pg_itm_in itm_in;
  Interval   *resInterval;

  /* stuff done only on the first call of the function */
  if (SRF_IS_FIRSTCALL())
  {
    TupleDesc tupdesc;
    MemoryContext oldcontext;

    /* create a function context for cross-call persistence */
    funcctx = SRF_FIRSTCALL_INIT();

    /*
     * switch to memory context appropriate for multiple function calls
     */
    oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

    /* allocate memory for user context */
    pindex = (int *) palloc(sizeof(int));
    *pindex = 0;
    funcctx->user_fctx = pindex;

    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
      elog(ERROR, "return type must be a row type");
    funcctx->tuple_desc = tupdesc;

    MemoryContextSwitchTo(oldcontext);
  }

  /* stuff done on every call of the function */
  funcctx = SRF_PERCALL_SETUP();
  pindex = (int *) funcctx->user_fctx;

  if (zoneabbrevtbl == NULL ||
    *pindex >= zoneabbrevtbl->numabbrevs)
    SRF_RETURN_DONE(funcctx);

  tp = zoneabbrevtbl->abbrevs + *pindex;

  switch (tp->type)
  {
    case TZ:
      gmtoffset = tp->value;
      is_dst = false;
      break;
    case DTZ:
      gmtoffset = tp->value;
      is_dst = true;
      break;
    case DYNTZ:
      {
        /* Determine the current meaning of the abbrev */
        pg_tz    *tzp;
        DateTimeErrorExtra extra;
        TimestampTz now;
        int     isdst;

        tzp = FetchDynamicTimeZone(zoneabbrevtbl, tp, &extra);
        if (tzp == NULL)
          DateTimeParseError(DTERR_BAD_ZONE_ABBREV, &extra,
                     NULL, NULL, NULL);
        now = GetCurrentTransactionStartTimestamp();
        gmtoffset = -DetermineTimeZoneAbbrevOffsetTS(now,
                               tp->token,
                               tzp,
                               &isdst);
        is_dst = (bool) isdst;
        break;
      }
    default:
      elog(ERROR, "unrecognized timezone type %d", (int) tp->type);
      gmtoffset = 0;    /* keep compiler quiet */
      is_dst = false;
      break;
  }

  /*
   * Convert name to text, using upcasing conversion that is the inverse of
   * what ParseDateTime() uses.
   */
  strlcpy(buffer, tp->token, sizeof(buffer));
  for (p = (unsigned char *) buffer; *p; p++)
    *p = pg_toupper(*p);

  values[0] = CStringGetTextDatum(buffer);

  /* Convert offset (in seconds) to an interval; can't overflow */
  MemSet(&itm_in, 0, sizeof(struct pg_itm_in));
  itm_in.tm_usec = (int64) gmtoffset * USECS_PER_SEC;
  resInterval = (Interval *) palloc(sizeof(Interval));
  (void) itmin2interval(&itm_in, resInterval);
  values[1] = IntervalPGetDatum(resInterval);

  values[2] = BoolGetDatum(is_dst);

  (*pindex)++;

  tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
  result = HeapTupleGetDatum(tuple);

  SRF_RETURN_NEXT(funcctx, result);
}

/*
 * This set-returning function reads all the available full time zones
 * and returns a set of (name, abbrev, utc_offset, is_dst).
 */
Datum
pg_timezone_names(PG_FUNCTION_ARGS)
{
  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
  pg_tzenum  *tzenum;
  pg_tz    *tz;
  Datum   values[4];
  bool    nulls[4] = {0};
  int     tzoff;
  struct pg_tm tm;
  fsec_t    fsec;
  const char *tzn;
  Interval   *resInterval;
  struct pg_itm_in itm_in;

  InitMaterializedSRF(fcinfo, 0);

  /* initialize timezone scanning code */
  tzenum = pg_tzenumerate_start();

  /* search for another zone to display */
  for (;;)
  {
    tz = pg_tzenumerate_next(tzenum);
    if (!tz)
      break;

    /* Convert now() to local time in this zone */
    if (timestamp2tm(GetCurrentTransactionStartTimestamp(),
             &tzoff, &tm, &fsec, &tzn, tz) != 0)
      continue;     /* ignore if conversion fails */

    /*
     * IANA's rather silly "Factory" time zone used to emit ridiculously
     * long "abbreviations" such as "Local time zone must be set--see zic
     * manual page" or "Local time zone must be set--use tzsetup".  While
     * modern versions of tzdb emit the much saner "-00", it seems some
     * benighted packagers are hacking the IANA data so that it continues
     * to produce these strings.  To prevent producing a weirdly wide
     * abbrev column, reject ridiculously long abbreviations.
     */
    if (tzn && strlen(tzn) > 31)
      continue;

    values[0] = CStringGetTextDatum(pg_get_timezone_name(tz));
    values[1] = CStringGetTextDatum(tzn ? tzn : "");

    /* Convert tzoff to an interval; can't overflow */
    MemSet(&itm_in, 0, sizeof(struct pg_itm_in));
    itm_in.tm_usec = (int64) -tzoff * USECS_PER_SEC;
    resInterval = (Interval *) palloc(sizeof(Interval));
    (void) itmin2interval(&itm_in, resInterval);
    values[2] = IntervalPGetDatum(resInterval);

    values[3] = BoolGetDatum(tm.tm_isdst > 0);

    tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
  }

  pg_tzenumerate_end(tzenum);
  return (Datum) 0;
}

Coverage Report

Created: 2025-08-12 06:43