/src/postgres/src/backend/access/spgist/spgtextproc.c

Source
/*-------------------------------------------------------------------------
 *
 * spgtextproc.c
 *    implementation of radix tree (compressed trie) over text
 *
 * In a text_ops SPGiST index, inner tuples can have a prefix which is the
 * common prefix of all strings indexed under that tuple.  The node labels
 * represent the next byte of the string(s) after the prefix.  Assuming we
 * always use the longest possible prefix, we will get more than one node
 * label unless the prefix length is restricted by SPGIST_MAX_PREFIX_LENGTH.
 *
 * To reconstruct the indexed string for any index entry, concatenate the
 * inner-tuple prefixes and node labels starting at the root and working
 * down to the leaf entry, then append the datum in the leaf entry.
 * (While descending the tree, "level" is the number of bytes reconstructed
 * so far.)
 *
 * However, there are two special cases for node labels: -1 indicates that
 * there are no more bytes after the prefix-so-far, and -2 indicates that we
 * had to split an existing allTheSame tuple (in such a case we have to create
 * a node label that doesn't correspond to any string byte).  In either case,
 * the node label does not contribute anything to the reconstructed string.
 *
 * Previously, we used a node label of zero for both special cases, but
 * this was problematic because one can't tell whether a string ending at
 * the current level can be pushed down into such a child node.  For
 * backwards compatibility, we still support such node labels for reading;
 * but no new entries will ever be pushed down into a zero-labeled child.
 * No new entries ever get pushed into a -2-labeled child, either.
 *
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *      src/backend/access/spgist/spgtextproc.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/spgist.h"
#include "catalog/pg_type.h"
#include "common/int.h"
#include "mb/pg_wchar.h"
#include "utils/datum.h"
#include "utils/fmgrprotos.h"
#include "utils/pg_locale.h"
#include "utils/varlena.h"
#include "varatt.h"


/*
 * In the worst case, an inner tuple in a text radix tree could have as many
 * as 258 nodes (one for each possible byte value, plus the two special
 * cases).  Each node can take 16 bytes on MAXALIGN=8 machines.  The inner
 * tuple must fit on an index page of size BLCKSZ.  Rather than assuming we
 * know the exact amount of overhead imposed by page headers, tuple headers,
 * etc, we leave 100 bytes for that (the actual overhead should be no more
 * than 56 bytes at this writing, so there is slop in this number).
 * So we can safely create prefixes up to BLCKSZ - 258 * 16 - 100 bytes long.
 * Unfortunately, because 258 * 16 is over 4K, there is no safe prefix length
 * when BLCKSZ is less than 8K; it is always possible to get "SPGiST inner
 * tuple size exceeds maximum" if there are too many distinct next-byte values
 * at a given place in the tree.  Since use of nonstandard block sizes appears
 * to be negligible in the field, we just live with that fact for now,
 * choosing a max prefix size of 32 bytes when BLCKSZ is configured smaller
 * than default.
 */
#define SPGIST_MAX_PREFIX_LENGTH  Max((int) (BLCKSZ - 258 * 16 - 100), 32)

/*
 * Strategy for collation aware operator on text is equal to btree strategy
 * plus value of 10.
 *
 * Current collation aware strategies and their corresponding btree strategies:
 * 11 BTLessStrategyNumber
 * 12 BTLessEqualStrategyNumber
 * 14 BTGreaterEqualStrategyNumber
 * 15 BTGreaterStrategyNumber
 */
#define SPG_STRATEGY_ADDITION (10)
#define SPG_IS_COLLATION_AWARE_STRATEGY(s) ((s) > SPG_STRATEGY_ADDITION \
                     && (s) != RTPrefixStrategyNumber)

/* Struct for sorting values in picksplit */
typedef struct spgNodePtr
{
  Datum   d;
  int     i;
  int16   c;
} spgNodePtr;


Datum
spg_text_config(PG_FUNCTION_ARGS)
{
#ifdef NOT_USED
  spgConfigIn *cfgin = (spgConfigIn *) PG_GETARG_POINTER(0);
#endif
  spgConfigOut *cfg = (spgConfigOut *) PG_GETARG_POINTER(1);

  cfg->prefixType = TEXTOID;
  cfg->labelType = INT2OID;
  cfg->canReturnData = true;
  cfg->longValuesOK = true; /* suffixing will shorten long values */
  PG_RETURN_VOID();
}

/*
 * Form a text datum from the given not-necessarily-null-terminated string,
 * using short varlena header format if possible
 */
static Datum
formTextDatum(const char *data, int datalen)
{
  char     *p;

  p = (char *) palloc(datalen + VARHDRSZ);

  if (datalen + VARHDRSZ_SHORT <= VARATT_SHORT_MAX)
  {
    SET_VARSIZE_SHORT(p, datalen + VARHDRSZ_SHORT);
    if (datalen)
      memcpy(p + VARHDRSZ_SHORT, data, datalen);
  }
  else
  {
    SET_VARSIZE(p, datalen + VARHDRSZ);
    memcpy(p + VARHDRSZ, data, datalen);
  }

  return PointerGetDatum(p);
}

/*
 * Find the length of the common prefix of a and b
 */
static int
commonPrefix(const char *a, const char *b, int lena, int lenb)
{
  int     i = 0;

  while (i < lena && i < lenb && *a == *b)
  {
    a++;
    b++;
    i++;
  }

  return i;
}

/*
 * Binary search an array of int16 datums for a match to c
 *
 * On success, *i gets the match location; on failure, it gets where to insert
 */
static bool
searchChar(const Datum *nodeLabels, int nNodes, int16 c, int *i)
{
  int     StopLow = 0,
        StopHigh = nNodes;

  while (StopLow < StopHigh)
  {
    int     StopMiddle = (StopLow + StopHigh) >> 1;
    int16   middle = DatumGetInt16(nodeLabels[StopMiddle]);

    if (c < middle)
      StopHigh = StopMiddle;
    else if (c > middle)
      StopLow = StopMiddle + 1;
    else
    {
      *i = StopMiddle;
      return true;
    }
  }

  *i = StopHigh;
  return false;
}

Datum
spg_text_choose(PG_FUNCTION_ARGS)
{
  spgChooseIn *in = (spgChooseIn *) PG_GETARG_POINTER(0);
  spgChooseOut *out = (spgChooseOut *) PG_GETARG_POINTER(1);
  text     *inText = DatumGetTextPP(in->datum);
  char     *inStr = VARDATA_ANY(inText);
  int     inSize = VARSIZE_ANY_EXHDR(inText);
  char     *prefixStr = NULL;
  int     prefixSize = 0;
  int     commonLen = 0;
  int16   nodeChar = 0;
  int     i = 0;

  /* Check for prefix match, set nodeChar to first byte after prefix */
  if (in->hasPrefix)
  {
    text     *prefixText = DatumGetTextPP(in->prefixDatum);

    prefixStr = VARDATA_ANY(prefixText);
    prefixSize = VARSIZE_ANY_EXHDR(prefixText);

    commonLen = commonPrefix(inStr + in->level,
                 prefixStr,
                 inSize - in->level,
                 prefixSize);

    if (commonLen == prefixSize)
    {
      if (inSize - in->level > commonLen)
        nodeChar = *(unsigned char *) (inStr + in->level + commonLen);
      else
        nodeChar = -1;
    }
    else
    {
      /* Must split tuple because incoming value doesn't match prefix */
      out->resultType = spgSplitTuple;

      if (commonLen == 0)
      {
        out->result.splitTuple.prefixHasPrefix = false;
      }
      else
      {
        out->result.splitTuple.prefixHasPrefix = true;
        out->result.splitTuple.prefixPrefixDatum =
          formTextDatum(prefixStr, commonLen);
      }
      out->result.splitTuple.prefixNNodes = 1;
      out->result.splitTuple.prefixNodeLabels = palloc_object(Datum);
      out->result.splitTuple.prefixNodeLabels[0] =
        Int16GetDatum(*(unsigned char *) (prefixStr + commonLen));

      out->result.splitTuple.childNodeN = 0;

      if (prefixSize - commonLen == 1)
      {
        out->result.splitTuple.postfixHasPrefix = false;
      }
      else
      {
        out->result.splitTuple.postfixHasPrefix = true;
        out->result.splitTuple.postfixPrefixDatum =
          formTextDatum(prefixStr + commonLen + 1,
                  prefixSize - commonLen - 1);
      }

      PG_RETURN_VOID();
    }
  }
  else if (inSize > in->level)
  {
    nodeChar = *(unsigned char *) (inStr + in->level);
  }
  else
  {
    nodeChar = -1;
  }

  /* Look up nodeChar in the node label array */
  if (searchChar(in->nodeLabels, in->nNodes, nodeChar, &i))
  {
    /*
     * Descend to existing node.  (If in->allTheSame, the core code will
     * ignore our nodeN specification here, but that's OK.  We still have
     * to provide the correct levelAdd and restDatum values, and those are
     * the same regardless of which node gets chosen by core.)
     */
    int     levelAdd;

    out->resultType = spgMatchNode;
    out->result.matchNode.nodeN = i;
    levelAdd = commonLen;
    if (nodeChar >= 0)
      levelAdd++;
    out->result.matchNode.levelAdd = levelAdd;
    if (inSize - in->level - levelAdd > 0)
      out->result.matchNode.restDatum =
        formTextDatum(inStr + in->level + levelAdd,
                inSize - in->level - levelAdd);
    else
      out->result.matchNode.restDatum =
        formTextDatum(NULL, 0);
  }
  else if (in->allTheSame)
  {
    /*
     * Can't use AddNode action, so split the tuple.  The upper tuple has
     * the same prefix as before and uses a dummy node label -2 for the
     * lower tuple.  The lower tuple has no prefix and the same node
     * labels as the original tuple.
     *
     * Note: it might seem tempting to shorten the upper tuple's prefix,
     * if it has one, then use its last byte as label for the lower tuple.
     * But that doesn't win since we know the incoming value matches the
     * whole prefix: we'd just end up splitting the lower tuple again.
     */
    out->resultType = spgSplitTuple;
    out->result.splitTuple.prefixHasPrefix = in->hasPrefix;
    out->result.splitTuple.prefixPrefixDatum = in->prefixDatum;
    out->result.splitTuple.prefixNNodes = 1;
    out->result.splitTuple.prefixNodeLabels = palloc_object(Datum);
    out->result.splitTuple.prefixNodeLabels[0] = Int16GetDatum(-2);
    out->result.splitTuple.childNodeN = 0;
    out->result.splitTuple.postfixHasPrefix = false;
  }
  else
  {
    /* Add a node for the not-previously-seen nodeChar value */
    out->resultType = spgAddNode;
    out->result.addNode.nodeLabel = Int16GetDatum(nodeChar);
    out->result.addNode.nodeN = i;
  }

  PG_RETURN_VOID();
}

/* qsort comparator to sort spgNodePtr structs by "c" */
static int
cmpNodePtr(const void *a, const void *b)
{
  const spgNodePtr *aa = (const spgNodePtr *) a;
  const spgNodePtr *bb = (const spgNodePtr *) b;

  return pg_cmp_s16(aa->c, bb->c);
}

Datum
spg_text_picksplit(PG_FUNCTION_ARGS)
{
  spgPickSplitIn *in = (spgPickSplitIn *) PG_GETARG_POINTER(0);
  spgPickSplitOut *out = (spgPickSplitOut *) PG_GETARG_POINTER(1);
  text     *text0 = DatumGetTextPP(in->datums[0]);
  int     i,
        commonLen;
  spgNodePtr *nodes;

  /* Identify longest common prefix, if any */
  commonLen = VARSIZE_ANY_EXHDR(text0);
  for (i = 1; i < in->nTuples && commonLen > 0; i++)
  {
    text     *texti = DatumGetTextPP(in->datums[i]);
    int     tmp = commonPrefix(VARDATA_ANY(text0),
                     VARDATA_ANY(texti),
                     VARSIZE_ANY_EXHDR(text0),
                     VARSIZE_ANY_EXHDR(texti));

    if (tmp < commonLen)
      commonLen = tmp;
  }

  /*
   * Limit the prefix length, if necessary, to ensure that the resulting
   * inner tuple will fit on a page.
   */
  commonLen = Min(commonLen, SPGIST_MAX_PREFIX_LENGTH);

  /* Set node prefix to be that string, if it's not empty */
  if (commonLen == 0)
  {
    out->hasPrefix = false;
  }
  else
  {
    out->hasPrefix = true;
    out->prefixDatum = formTextDatum(VARDATA_ANY(text0), commonLen);
  }

  /* Extract the node label (first non-common byte) from each value */
  nodes = palloc_array(spgNodePtr, in->nTuples);

  for (i = 0; i < in->nTuples; i++)
  {
    text     *texti = DatumGetTextPP(in->datums[i]);

    if (commonLen < VARSIZE_ANY_EXHDR(texti))
      nodes[i].c = *(unsigned char *) (VARDATA_ANY(texti) + commonLen);
    else
      nodes[i].c = -1; /* use -1 if string is all common */
    nodes[i].i = i;
    nodes[i].d = in->datums[i];
  }

  /*
   * Sort by label values so that we can group the values into nodes.  This
   * also ensures that the nodes are ordered by label value, allowing the
   * use of binary search in searchChar.
   */
  qsort(nodes, in->nTuples, sizeof(*nodes), cmpNodePtr);

  /* And emit results */
  out->nNodes = 0;
  out->nodeLabels = palloc_array(Datum, in->nTuples);
  out->mapTuplesToNodes = palloc_array(int, in->nTuples);
  out->leafTupleDatums = palloc_array(Datum, in->nTuples);

  for (i = 0; i < in->nTuples; i++)
  {
    text     *texti = DatumGetTextPP(nodes[i].d);
    Datum   leafD;

    if (i == 0 || nodes[i].c != nodes[i - 1].c)
    {
      out->nodeLabels[out->nNodes] = Int16GetDatum(nodes[i].c);
      out->nNodes++;
    }

    if (commonLen < VARSIZE_ANY_EXHDR(texti))
      leafD = formTextDatum(VARDATA_ANY(texti) + commonLen + 1,
                  VARSIZE_ANY_EXHDR(texti) - commonLen - 1);
    else
      leafD = formTextDatum(NULL, 0);

    out->leafTupleDatums[nodes[i].i] = leafD;
    out->mapTuplesToNodes[nodes[i].i] = out->nNodes - 1;
  }

  PG_RETURN_VOID();
}

Datum
spg_text_inner_consistent(PG_FUNCTION_ARGS)
{
  spgInnerConsistentIn *in = (spgInnerConsistentIn *) PG_GETARG_POINTER(0);
  spgInnerConsistentOut *out = (spgInnerConsistentOut *) PG_GETARG_POINTER(1);
  bool    collate_is_c = pg_newlocale_from_collation(PG_GET_COLLATION())->collate_is_c;
  text     *reconstructedValue;
  text     *reconstrText;
  int     maxReconstrLen;
  text     *prefixText = NULL;
  int     prefixSize = 0;
  int     i;

  /*
   * Reconstruct values represented at this tuple, including parent data,
   * prefix of this tuple if any, and the node label if it's non-dummy.
   * in->level should be the length of the previously reconstructed value,
   * and the number of bytes added here is prefixSize or prefixSize + 1.
   *
   * Note: we assume that in->reconstructedValue isn't toasted and doesn't
   * have a short varlena header.  This is okay because it must have been
   * created by a previous invocation of this routine, and we always emit
   * long-format reconstructed values.
   */
  reconstructedValue = (text *) DatumGetPointer(in->reconstructedValue);
  Assert(reconstructedValue == NULL ? in->level == 0 :
       VARSIZE_ANY_EXHDR(reconstructedValue) == in->level);

  maxReconstrLen = in->level + 1;
  if (in->hasPrefix)
  {
    prefixText = DatumGetTextPP(in->prefixDatum);
    prefixSize = VARSIZE_ANY_EXHDR(prefixText);
    maxReconstrLen += prefixSize;
  }

  reconstrText = palloc(VARHDRSZ + maxReconstrLen);
  SET_VARSIZE(reconstrText, VARHDRSZ + maxReconstrLen);

  if (in->level)
    memcpy(VARDATA(reconstrText),
         VARDATA(reconstructedValue),
         in->level);
  if (prefixSize)
    memcpy(((char *) VARDATA(reconstrText)) + in->level,
         VARDATA_ANY(prefixText),
         prefixSize);
  /* last byte of reconstrText will be filled in below */

  /*
   * Scan the child nodes.  For each one, complete the reconstructed value
   * and see if it's consistent with the query.  If so, emit an entry into
   * the output arrays.
   */
  out->nodeNumbers = palloc_array(int, in->nNodes);
  out->levelAdds = palloc_array(int, in->nNodes);
  out->reconstructedValues = palloc_array(Datum, in->nNodes);
  out->nNodes = 0;

  for (i = 0; i < in->nNodes; i++)
  {
    int16   nodeChar = DatumGetInt16(in->nodeLabels[i]);
    int     thisLen;
    bool    res = true;
    int     j;

    /* If nodeChar is a dummy value, don't include it in data */
    if (nodeChar <= 0)
      thisLen = maxReconstrLen - 1;
    else
    {
      ((unsigned char *) VARDATA(reconstrText))[maxReconstrLen - 1] = nodeChar;
      thisLen = maxReconstrLen;
    }

    for (j = 0; j < in->nkeys; j++)
    {
      StrategyNumber strategy = in->scankeys[j].sk_strategy;
      text     *inText;
      int     inSize;
      int     r;

      /*
       * If it's a collation-aware operator, but the collation is C, we
       * can treat it as non-collation-aware.  With non-C collation we
       * need to traverse whole tree :-( so there's no point in making
       * any check here.  (Note also that our reconstructed value may
       * well end with a partial multibyte character, so that applying
       * any encoding-sensitive test to it would be risky anyhow.)
       */
      if (SPG_IS_COLLATION_AWARE_STRATEGY(strategy))
      {
        if (collate_is_c)
          strategy -= SPG_STRATEGY_ADDITION;
        else
          continue;
      }

      inText = DatumGetTextPP(in->scankeys[j].sk_argument);
      inSize = VARSIZE_ANY_EXHDR(inText);

      r = memcmp(VARDATA(reconstrText), VARDATA_ANY(inText),
             Min(inSize, thisLen));

      switch (strategy)
      {
        case BTLessStrategyNumber:
        case BTLessEqualStrategyNumber:
          if (r > 0)
            res = false;
          break;
        case BTEqualStrategyNumber:
          if (r != 0 || inSize < thisLen)
            res = false;
          break;
        case BTGreaterEqualStrategyNumber:
        case BTGreaterStrategyNumber:
          if (r < 0)
            res = false;
          break;
        case RTPrefixStrategyNumber:
          if (r != 0)
            res = false;
          break;
        default:
          elog(ERROR, "unrecognized strategy number: %d",
             in->scankeys[j].sk_strategy);
          break;
      }

      if (!res)
        break;     /* no need to consider remaining conditions */
    }

    if (res)
    {
      out->nodeNumbers[out->nNodes] = i;
      out->levelAdds[out->nNodes] = thisLen - in->level;
      SET_VARSIZE(reconstrText, VARHDRSZ + thisLen);
      out->reconstructedValues[out->nNodes] =
        datumCopy(PointerGetDatum(reconstrText), false, -1);
      out->nNodes++;
    }
  }

  PG_RETURN_VOID();
}

Datum
spg_text_leaf_consistent(PG_FUNCTION_ARGS)
{
  spgLeafConsistentIn *in = (spgLeafConsistentIn *) PG_GETARG_POINTER(0);
  spgLeafConsistentOut *out = (spgLeafConsistentOut *) PG_GETARG_POINTER(1);
  int     level = in->level;
  text     *leafValue,
         *reconstrValue = NULL;
  char     *fullValue;
  int     fullLen;
  bool    res;
  int     j;

  /* all tests are exact */
  out->recheck = false;

  leafValue = DatumGetTextPP(in->leafDatum);

  /* As above, in->reconstructedValue isn't toasted or short. */
  if (DatumGetPointer(in->reconstructedValue))
    reconstrValue = (text *) DatumGetPointer(in->reconstructedValue);

  Assert(reconstrValue == NULL ? level == 0 :
       VARSIZE_ANY_EXHDR(reconstrValue) == level);

  /* Reconstruct the full string represented by this leaf tuple */
  fullLen = level + VARSIZE_ANY_EXHDR(leafValue);
  if (VARSIZE_ANY_EXHDR(leafValue) == 0 && level > 0)
  {
    fullValue = VARDATA(reconstrValue);
    out->leafValue = PointerGetDatum(reconstrValue);
  }
  else
  {
    text     *fullText = palloc(VARHDRSZ + fullLen);

    SET_VARSIZE(fullText, VARHDRSZ + fullLen);
    fullValue = VARDATA(fullText);
    if (level)
      memcpy(fullValue, VARDATA(reconstrValue), level);
    if (VARSIZE_ANY_EXHDR(leafValue) > 0)
      memcpy(fullValue + level, VARDATA_ANY(leafValue),
           VARSIZE_ANY_EXHDR(leafValue));
    out->leafValue = PointerGetDatum(fullText);
  }

  /* Perform the required comparison(s) */
  res = true;
  for (j = 0; j < in->nkeys; j++)
  {
    StrategyNumber strategy = in->scankeys[j].sk_strategy;
    text     *query = DatumGetTextPP(in->scankeys[j].sk_argument);
    int     queryLen = VARSIZE_ANY_EXHDR(query);
    int     r;

    if (strategy == RTPrefixStrategyNumber)
    {
      /*
       * if level >= length of query then reconstrValue must begin with
       * query (prefix) string, so we don't need to check it again.
       */
      res = (level >= queryLen) ||
        DatumGetBool(DirectFunctionCall2Coll(text_starts_with,
                           PG_GET_COLLATION(),
                           out->leafValue,
                           PointerGetDatum(query)));

      if (!res)     /* no need to consider remaining conditions */
        break;

      continue;
    }

    if (SPG_IS_COLLATION_AWARE_STRATEGY(strategy))
    {
      /* Collation-aware comparison */
      strategy -= SPG_STRATEGY_ADDITION;

      /* If asserts enabled, verify encoding of reconstructed string */
      Assert(pg_verifymbstr(fullValue, fullLen, false));

      r = varstr_cmp(fullValue, fullLen,
               VARDATA_ANY(query), queryLen,
               PG_GET_COLLATION());
    }
    else
    {
      /* Non-collation-aware comparison */
      r = memcmp(fullValue, VARDATA_ANY(query), Min(queryLen, fullLen));

      if (r == 0)
      {
        if (queryLen > fullLen)
          r = -1;
        else if (queryLen < fullLen)
          r = 1;
      }
    }

    switch (strategy)
    {
      case BTLessStrategyNumber:
        res = (r < 0);
        break;
      case BTLessEqualStrategyNumber:
        res = (r <= 0);
        break;
      case BTEqualStrategyNumber:
        res = (r == 0);
        break;
      case BTGreaterEqualStrategyNumber:
        res = (r >= 0);
        break;
      case BTGreaterStrategyNumber:
        res = (r > 0);
        break;
      default:
        elog(ERROR, "unrecognized strategy number: %d",
           in->scankeys[j].sk_strategy);
        res = false;
        break;
    }

    if (!res)
      break;       /* no need to consider remaining conditions */
  }

  PG_RETURN_BOOL(res);
}

Coverage Report

Created: 2026-08-14 06:37