/src/postgres/src/backend/commands/extension.c

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/*-------------------------------------------------------------------------
 *
 * extension.c
 *    Commands to manipulate extensions
 *
 * Extensions in PostgreSQL allow management of collections of SQL objects.
 *
 * All we need internally to manage an extension is an OID so that the
 * dependent objects can be associated with it.  An extension is created by
 * populating the pg_extension catalog from a "control" file.
 * The extension control file is parsed with the same parser we use for
 * postgresql.conf.  An extension also has an installation script file,
 * containing SQL commands to create the extension's objects.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/commands/extension.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <dirent.h>
#include <limits.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <unistd.h>

#include "access/genam.h"
#include "access/htup_details.h"
#include "access/relation.h"
#include "access/table.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_database.h"
#include "catalog/pg_depend.h"
#include "catalog/pg_extension.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_type.h"
#include "commands/alter.h"
#include "commands/comment.h"
#include "commands/defrem.h"
#include "commands/extension.h"
#include "commands/schemacmds.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/pg_list.h"
#include "nodes/queryjumble.h"
#include "storage/fd.h"
#include "tcop/utility.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/conffiles.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/varlena.h"


/* GUC */
char     *Extension_control_path;

/* Globally visible state variables */
bool    creating_extension = false;
Oid     CurrentExtensionObject = InvalidOid;

/*
 * Internal data structure to hold the results of parsing a control file
 */
typedef struct ExtensionControlFile
{
  char     *name;     /* name of the extension */
  char     *basedir;    /* base directory where control and script
                 * files are located */
  char     *control_dir;  /* directory where control file was found */
  char     *directory;    /* directory for script files */
  char     *default_version;  /* default install target version, if any */
  char     *module_pathname;  /* string to substitute for
                   * MODULE_PATHNAME */
  char     *comment;    /* comment, if any */
  char     *schema;     /* target schema (allowed if !relocatable) */
  bool    relocatable;  /* is ALTER EXTENSION SET SCHEMA supported? */
  bool    superuser;    /* must be superuser to install? */
  bool    trusted;    /* allow becoming superuser on the fly? */
  int     encoding;   /* encoding of the script file, or -1 */
  List     *requires;   /* names of prerequisite extensions */
  List     *no_relocate;  /* names of prerequisite extensions that
                 * should not be relocated */
} ExtensionControlFile;

/*
 * Internal data structure for update path information
 */
typedef struct ExtensionVersionInfo
{
  char     *name;     /* name of the starting version */
  List     *reachable;    /* List of ExtensionVersionInfo's */
  bool    installable;  /* does this version have an install script? */
  /* working state for Dijkstra's algorithm: */
  bool    distance_known; /* is distance from start known yet? */
  int     distance;   /* current worst-case distance estimate */
  struct ExtensionVersionInfo *previous;  /* current best predecessor */
} ExtensionVersionInfo;

/*
 * Information for script_error_callback()
 */
typedef struct
{
  const char *sql;      /* entire script file contents */
  const char *filename;   /* script file pathname */
  ParseLoc  stmt_location;  /* current stmt start loc, or -1 if unknown */
  ParseLoc  stmt_len;   /* length in bytes; 0 means "rest of string" */
} script_error_callback_arg;

/* Local functions */
static List *find_update_path(List *evi_list,
                ExtensionVersionInfo *evi_start,
                ExtensionVersionInfo *evi_target,
                bool reject_indirect,
                bool reinitialize);
static Oid  get_required_extension(char *reqExtensionName,
                   char *extensionName,
                   char *origSchemaName,
                   bool cascade,
                   List *parents,
                   bool is_create);
static void get_available_versions_for_extension(ExtensionControlFile *pcontrol,
                         Tuplestorestate *tupstore,
                         TupleDesc tupdesc);
static Datum convert_requires_to_datum(List *requires);
static void ApplyExtensionUpdates(Oid extensionOid,
                  ExtensionControlFile *pcontrol,
                  const char *initialVersion,
                  List *updateVersions,
                  char *origSchemaName,
                  bool cascade,
                  bool is_create);
static void ExecAlterExtensionContentsRecurse(AlterExtensionContentsStmt *stmt,
                        ObjectAddress extension,
                        ObjectAddress object);
static char *read_whole_file(const char *filename, int *length);
static ExtensionControlFile *new_ExtensionControlFile(const char *extname);

char     *find_in_paths(const char *basename, List *paths);

/*
 * get_extension_oid - given an extension name, look up the OID
 *
 * If missing_ok is false, throw an error if extension name not found.  If
 * true, just return InvalidOid.
 */
Oid
get_extension_oid(const char *extname, bool missing_ok)
{
  Oid     result;

  result = GetSysCacheOid1(EXTENSIONNAME, Anum_pg_extension_oid,
               CStringGetDatum(extname));

  if (!OidIsValid(result) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("extension \"%s\" does not exist",
            extname)));

  return result;
}

/*
 * get_extension_name - given an extension OID, look up the name
 *
 * Returns a palloc'd string, or NULL if no such extension.
 */
char *
get_extension_name(Oid ext_oid)
{
  char     *result;
  HeapTuple tuple;

  tuple = SearchSysCache1(EXTENSIONOID, ObjectIdGetDatum(ext_oid));

  if (!HeapTupleIsValid(tuple))
    return NULL;

  result = pstrdup(NameStr(((Form_pg_extension) GETSTRUCT(tuple))->extname));
  ReleaseSysCache(tuple);

  return result;
}

/*
 * get_extension_schema - given an extension OID, fetch its extnamespace
 *
 * Returns InvalidOid if no such extension.
 */
Oid
get_extension_schema(Oid ext_oid)
{
  Oid     result;
  HeapTuple tuple;

  tuple = SearchSysCache1(EXTENSIONOID, ObjectIdGetDatum(ext_oid));

  if (!HeapTupleIsValid(tuple))
    return InvalidOid;

  result = ((Form_pg_extension) GETSTRUCT(tuple))->extnamespace;
  ReleaseSysCache(tuple);

  return result;
}

/*
 * Utility functions to check validity of extension and version names
 */
static void
check_valid_extension_name(const char *extensionname)
{
  int     namelen = strlen(extensionname);

  /*
   * Disallow empty names (the parser rejects empty identifiers anyway, but
   * let's check).
   */
  if (namelen == 0)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension name: \"%s\"", extensionname),
         errdetail("Extension names must not be empty.")));

  /*
   * No double dashes, since that would make script filenames ambiguous.
   */
  if (strstr(extensionname, "--"))
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension name: \"%s\"", extensionname),
         errdetail("Extension names must not contain \"--\".")));

  /*
   * No leading or trailing dash either.  (We could probably allow this, but
   * it would require much care in filename parsing and would make filenames
   * visually if not formally ambiguous.  Since there's no real-world use
   * case, let's just forbid it.)
   */
  if (extensionname[0] == '-' || extensionname[namelen - 1] == '-')
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension name: \"%s\"", extensionname),
         errdetail("Extension names must not begin or end with \"-\".")));

  /*
   * No directory separators either (this is sufficient to prevent ".."
   * style attacks).
   */
  if (first_dir_separator(extensionname) != NULL)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension name: \"%s\"", extensionname),
         errdetail("Extension names must not contain directory separator characters.")));
}

static void
check_valid_version_name(const char *versionname)
{
  int     namelen = strlen(versionname);

  /*
   * Disallow empty names (we could possibly allow this, but there seems
   * little point).
   */
  if (namelen == 0)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension version name: \"%s\"", versionname),
         errdetail("Version names must not be empty.")));

  /*
   * No double dashes, since that would make script filenames ambiguous.
   */
  if (strstr(versionname, "--"))
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension version name: \"%s\"", versionname),
         errdetail("Version names must not contain \"--\".")));

  /*
   * No leading or trailing dash either.
   */
  if (versionname[0] == '-' || versionname[namelen - 1] == '-')
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension version name: \"%s\"", versionname),
         errdetail("Version names must not begin or end with \"-\".")));

  /*
   * No directory separators either (this is sufficient to prevent ".."
   * style attacks).
   */
  if (first_dir_separator(versionname) != NULL)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid extension version name: \"%s\"", versionname),
         errdetail("Version names must not contain directory separator characters.")));
}

/*
 * Utility functions to handle extension-related path names
 */
static bool
is_extension_control_filename(const char *filename)
{
  const char *extension = strrchr(filename, '.');

  return (extension != NULL) && (strcmp(extension, ".control") == 0);
}

static bool
is_extension_script_filename(const char *filename)
{
  const char *extension = strrchr(filename, '.');

  return (extension != NULL) && (strcmp(extension, ".sql") == 0);
}

/*
 * Return a list of directories declared on extension_control_path GUC.
 */
static List *
get_extension_control_directories(void)
{
  char    sharepath[MAXPGPATH];
  char     *system_dir;
  char     *ecp;
  List     *paths = NIL;

  get_share_path(my_exec_path, sharepath);

  system_dir = psprintf("%s/extension", sharepath);

  if (strlen(Extension_control_path) == 0)
  {
    paths = lappend(paths, system_dir);
  }
  else
  {
    /* Duplicate the string so we can modify it */
    ecp = pstrdup(Extension_control_path);

    for (;;)
    {
      int     len;
      char     *mangled;
      char     *piece = first_path_var_separator(ecp);

      /* Get the length of the next path on ecp */
      if (piece == NULL)
        len = strlen(ecp);
      else
        len = piece - ecp;

      /* Copy the next path found on ecp */
      piece = palloc(len + 1);
      strlcpy(piece, ecp, len + 1);

      /*
       * Substitute the path macro if needed or append "extension"
       * suffix if it is a custom extension control path.
       */
      if (strcmp(piece, "$system") == 0)
        mangled = substitute_path_macro(piece, "$system", system_dir);
      else
        mangled = psprintf("%s/extension", piece);

      pfree(piece);

      /* Canonicalize the path based on the OS and add to the list */
      canonicalize_path(mangled);
      paths = lappend(paths, mangled);

      /* Break if ecp is empty or move to the next path on ecp */
      if (ecp[len] == '\0')
        break;
      else
        ecp += len + 1;
    }
  }

  return paths;
}

/*
 * Find control file for extension with name in control->name, looking in the
 * path.  Return the full file name, or NULL if not found.  If found, the
 * directory is recorded in control->control_dir.
 */
static char *
find_extension_control_filename(ExtensionControlFile *control)
{
  char     *basename;
  char     *result;
  List     *paths;

  Assert(control->name);

  basename = psprintf("%s.control", control->name);

  paths = get_extension_control_directories();
  result = find_in_paths(basename, paths);

  if (result)
  {
    const char *p;

    p = strrchr(result, '/');
    Assert(p);
    control->control_dir = pnstrdup(result, p - result);
  }

  return result;
}

static char *
get_extension_script_directory(ExtensionControlFile *control)
{
  /*
   * The directory parameter can be omitted, absolute, or relative to the
   * installation's base directory, which can be the sharedir or a custom
   * path that it was set extension_control_path. It depends where the
   * .control file was found.
   */
  if (!control->directory)
    return pstrdup(control->control_dir);

  if (is_absolute_path(control->directory))
    return pstrdup(control->directory);

  Assert(control->basedir != NULL);
  return psprintf("%s/%s", control->basedir, control->directory);
}

static char *
get_extension_aux_control_filename(ExtensionControlFile *control,
                   const char *version)
{
  char     *result;
  char     *scriptdir;

  scriptdir = get_extension_script_directory(control);

  result = (char *) palloc(MAXPGPATH);
  snprintf(result, MAXPGPATH, "%s/%s--%s.control",
       scriptdir, control->name, version);

  pfree(scriptdir);

  return result;
}

static char *
get_extension_script_filename(ExtensionControlFile *control,
                const char *from_version, const char *version)
{
  char     *result;
  char     *scriptdir;

  scriptdir = get_extension_script_directory(control);

  result = (char *) palloc(MAXPGPATH);
  if (from_version)
    snprintf(result, MAXPGPATH, "%s/%s--%s--%s.sql",
         scriptdir, control->name, from_version, version);
  else
    snprintf(result, MAXPGPATH, "%s/%s--%s.sql",
         scriptdir, control->name, version);

  pfree(scriptdir);

  return result;
}


/*
 * Parse contents of primary or auxiliary control file, and fill in
 * fields of *control.  We parse primary file if version == NULL,
 * else the optional auxiliary file for that version.
 *
 * The control file will be search on Extension_control_path paths if
 * control->control_dir is NULL, otherwise it will use the value of control_dir
 * to read and parse the .control file, so it assume that the control_dir is a
 * valid path for the control file being parsed.
 *
 * Control files are supposed to be very short, half a dozen lines,
 * so we don't worry about memory allocation risks here.  Also we don't
 * worry about what encoding it's in; all values are expected to be ASCII.
 */
static void
parse_extension_control_file(ExtensionControlFile *control,
               const char *version)
{
  char     *filename;
  FILE     *file;
  ConfigVariable *item,
         *head = NULL,
         *tail = NULL;

  /*
   * Locate the file to read.  Auxiliary files are optional.
   */
  if (version)
    filename = get_extension_aux_control_filename(control, version);
  else
  {
    /*
     * If control_dir is already set, use it, else do a path search.
     */
    if (control->control_dir)
    {
      filename = psprintf("%s/%s.control", control->control_dir, control->name);
    }
    else
      filename = find_extension_control_filename(control);
  }

  if (!filename)
  {
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("extension \"%s\" is not available", control->name),
         errhint("The extension must first be installed on the system where PostgreSQL is running.")));
  }

  /* Assert that the control_dir ends with /extension */
  Assert(control->control_dir != NULL);
  Assert(strcmp(control->control_dir + strlen(control->control_dir) - strlen("/extension"), "/extension") == 0);

  control->basedir = pnstrdup(
                control->control_dir,
                strlen(control->control_dir) - strlen("/extension"));

  if ((file = AllocateFile(filename, "r")) == NULL)
  {
    /* no complaint for missing auxiliary file */
    if (errno == ENOENT && version)
    {
      pfree(filename);
      return;
    }

    ereport(ERROR,
        (errcode_for_file_access(),
         errmsg("could not open extension control file \"%s\": %m",
            filename)));
  }

  /*
   * Parse the file content, using GUC's file parsing code.  We need not
   * check the return value since any errors will be thrown at ERROR level.
   */
  (void) ParseConfigFp(file, filename, CONF_FILE_START_DEPTH, ERROR,
             &head, &tail);

  FreeFile(file);

  /*
   * Convert the ConfigVariable list into ExtensionControlFile entries.
   */
  for (item = head; item != NULL; item = item->next)
  {
    if (strcmp(item->name, "directory") == 0)
    {
      if (version)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
             errmsg("parameter \"%s\" cannot be set in a secondary extension control file",
                item->name)));

      control->directory = pstrdup(item->value);
    }
    else if (strcmp(item->name, "default_version") == 0)
    {
      if (version)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
             errmsg("parameter \"%s\" cannot be set in a secondary extension control file",
                item->name)));

      control->default_version = pstrdup(item->value);
    }
    else if (strcmp(item->name, "module_pathname") == 0)
    {
      control->module_pathname = pstrdup(item->value);
    }
    else if (strcmp(item->name, "comment") == 0)
    {
      control->comment = pstrdup(item->value);
    }
    else if (strcmp(item->name, "schema") == 0)
    {
      control->schema = pstrdup(item->value);
    }
    else if (strcmp(item->name, "relocatable") == 0)
    {
      if (!parse_bool(item->value, &control->relocatable))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
             errmsg("parameter \"%s\" requires a Boolean value",
                item->name)));
    }
    else if (strcmp(item->name, "superuser") == 0)
    {
      if (!parse_bool(item->value, &control->superuser))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
             errmsg("parameter \"%s\" requires a Boolean value",
                item->name)));
    }
    else if (strcmp(item->name, "trusted") == 0)
    {
      if (!parse_bool(item->value, &control->trusted))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
             errmsg("parameter \"%s\" requires a Boolean value",
                item->name)));
    }
    else if (strcmp(item->name, "encoding") == 0)
    {
      control->encoding = pg_valid_server_encoding(item->value);
      if (control->encoding < 0)
        ereport(ERROR,
            (errcode(ERRCODE_UNDEFINED_OBJECT),
             errmsg("\"%s\" is not a valid encoding name",
                item->value)));
    }
    else if (strcmp(item->name, "requires") == 0)
    {
      /* Need a modifiable copy of string */
      char     *rawnames = pstrdup(item->value);

      /* Parse string into list of identifiers */
      if (!SplitIdentifierString(rawnames, ',', &control->requires))
      {
        /* syntax error in name list */
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
             errmsg("parameter \"%s\" must be a list of extension names",
                item->name)));
      }
    }
    else if (strcmp(item->name, "no_relocate") == 0)
    {
      /* Need a modifiable copy of string */
      char     *rawnames = pstrdup(item->value);

      /* Parse string into list of identifiers */
      if (!SplitIdentifierString(rawnames, ',', &control->no_relocate))
      {
        /* syntax error in name list */
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
             errmsg("parameter \"%s\" must be a list of extension names",
                item->name)));
      }
    }
    else
      ereport(ERROR,
          (errcode(ERRCODE_SYNTAX_ERROR),
           errmsg("unrecognized parameter \"%s\" in file \"%s\"",
              item->name, filename)));
  }

  FreeConfigVariables(head);

  if (control->relocatable && control->schema != NULL)
    ereport(ERROR,
        (errcode(ERRCODE_SYNTAX_ERROR),
         errmsg("parameter \"schema\" cannot be specified when \"relocatable\" is true")));

  pfree(filename);
}

/*
 * Read the primary control file for the specified extension.
 */
static ExtensionControlFile *
read_extension_control_file(const char *extname)
{
  ExtensionControlFile *control = new_ExtensionControlFile(extname);

  /*
   * Parse the primary control file.
   */
  parse_extension_control_file(control, NULL);

  return control;
}

/*
 * Read the auxiliary control file for the specified extension and version.
 *
 * Returns a new modified ExtensionControlFile struct; the original struct
 * (reflecting just the primary control file) is not modified.
 */
static ExtensionControlFile *
read_extension_aux_control_file(const ExtensionControlFile *pcontrol,
                const char *version)
{
  ExtensionControlFile *acontrol;

  /*
   * Flat-copy the struct.  Pointer fields share values with original.
   */
  acontrol = (ExtensionControlFile *) palloc(sizeof(ExtensionControlFile));
  memcpy(acontrol, pcontrol, sizeof(ExtensionControlFile));

  /*
   * Parse the auxiliary control file, overwriting struct fields
   */
  parse_extension_control_file(acontrol, version);

  return acontrol;
}

/*
 * Read an SQL script file into a string, and convert to database encoding
 */
static char *
read_extension_script_file(const ExtensionControlFile *control,
               const char *filename)
{
  int     src_encoding;
  char     *src_str;
  char     *dest_str;
  int     len;

  src_str = read_whole_file(filename, &len);

  /* use database encoding if not given */
  if (control->encoding < 0)
    src_encoding = GetDatabaseEncoding();
  else
    src_encoding = control->encoding;

  /* make sure that source string is valid in the expected encoding */
  (void) pg_verify_mbstr(src_encoding, src_str, len, false);

  /*
   * Convert the encoding to the database encoding. read_whole_file
   * null-terminated the string, so if no conversion happens the string is
   * valid as is.
   */
  dest_str = pg_any_to_server(src_str, len, src_encoding);

  return dest_str;
}

/*
 * error context callback for failures in script-file execution
 */
static void
script_error_callback(void *arg)
{
  script_error_callback_arg *callback_arg = (script_error_callback_arg *) arg;
  const char *query = callback_arg->sql;
  int     location = callback_arg->stmt_location;
  int     len = callback_arg->stmt_len;
  int     syntaxerrposition;
  const char *lastslash;

  /*
   * If there is a syntax error position, convert to internal syntax error;
   * otherwise report the current query as an item of context stack.
   *
   * Note: we'll provide no context except the filename if there's neither
   * an error position nor any known current query.  That shouldn't happen
   * though: all errors reported during raw parsing should come with an
   * error position.
   */
  syntaxerrposition = geterrposition();
  if (syntaxerrposition > 0)
  {
    /*
     * If we do not know the bounds of the current statement (as would
     * happen for an error occurring during initial raw parsing), we have
     * to use a heuristic to decide how much of the script to show.  We'll
     * also use the heuristic in the unlikely case that syntaxerrposition
     * is outside what we think the statement bounds are.
     */
    if (location < 0 || syntaxerrposition < location ||
      (len > 0 && syntaxerrposition > location + len))
    {
      /*
       * Our heuristic is pretty simple: look for semicolon-newline
       * sequences, and break at the last one strictly before
       * syntaxerrposition and the first one strictly after.  It's
       * certainly possible to fool this with semicolon-newline embedded
       * in a string literal, but it seems better to do this than to
       * show the entire extension script.
       *
       * Notice we cope with Windows-style newlines (\r\n) regardless of
       * platform.  This is because there might be such newlines in
       * script files on other platforms.
       */
      int     slen = strlen(query);

      location = len = 0;
      for (int loc = 0; loc < slen; loc++)
      {
        if (query[loc] != ';')
          continue;
        if (query[loc + 1] == '\r')
          loc++;
        if (query[loc + 1] == '\n')
        {
          int     bkpt = loc + 2;

          if (bkpt < syntaxerrposition)
            location = bkpt;
          else if (bkpt > syntaxerrposition)
          {
            len = bkpt - location;
            break;  /* no need to keep searching */
          }
        }
      }
    }

    /* Trim leading/trailing whitespace, for consistency */
    query = CleanQuerytext(query, &location, &len);

    /*
     * Adjust syntaxerrposition.  It shouldn't be pointing into the
     * whitespace we just trimmed, but cope if it is.
     */
    syntaxerrposition -= location;
    if (syntaxerrposition < 0)
      syntaxerrposition = 0;
    else if (syntaxerrposition > len)
      syntaxerrposition = len;

    /* And report. */
    errposition(0);
    internalerrposition(syntaxerrposition);
    internalerrquery(pnstrdup(query, len));
  }
  else if (location >= 0)
  {
    /*
     * Since no syntax cursor will be shown, it's okay and helpful to trim
     * the reported query string to just the current statement.
     */
    query = CleanQuerytext(query, &location, &len);
    errcontext("SQL statement \"%.*s\"", len, query);
  }

  /*
   * Trim the reported file name to remove the path.  We know that
   * get_extension_script_filename() inserted a '/', regardless of whether
   * we're on Windows.
   */
  lastslash = strrchr(callback_arg->filename, '/');
  if (lastslash)
    lastslash++;
  else
    lastslash = callback_arg->filename; /* shouldn't happen, but cope */

  /*
   * If we have a location (which, as said above, we really always should)
   * then report a line number to aid in localizing problems in big scripts.
   */
  if (location >= 0)
  {
    int     linenumber = 1;

    for (query = callback_arg->sql; *query; query++)
    {
      if (--location < 0)
        break;
      if (*query == '\n')
        linenumber++;
    }
    errcontext("extension script file \"%s\", near line %d",
           lastslash, linenumber);
  }
  else
    errcontext("extension script file \"%s\"", lastslash);
}

/*
 * Execute given SQL string.
 *
 * The filename the string came from is also provided, for error reporting.
 *
 * Note: it's tempting to just use SPI to execute the string, but that does
 * not work very well.  The really serious problem is that SPI will parse,
 * analyze, and plan the whole string before executing any of it; of course
 * this fails if there are any plannable statements referring to objects
 * created earlier in the script.  A lesser annoyance is that SPI insists
 * on printing the whole string as errcontext in case of any error, and that
 * could be very long.
 */
static void
execute_sql_string(const char *sql, const char *filename)
{
  script_error_callback_arg callback_arg;
  ErrorContextCallback scripterrcontext;
  List     *raw_parsetree_list;
  DestReceiver *dest;
  ListCell   *lc1;

  /*
   * Setup error traceback support for ereport().
   */
  callback_arg.sql = sql;
  callback_arg.filename = filename;
  callback_arg.stmt_location = -1;
  callback_arg.stmt_len = -1;

  scripterrcontext.callback = script_error_callback;
  scripterrcontext.arg = (void *) &callback_arg;
  scripterrcontext.previous = error_context_stack;
  error_context_stack = &scripterrcontext;

  /*
   * Parse the SQL string into a list of raw parse trees.
   */
  raw_parsetree_list = pg_parse_query(sql);

  /* All output from SELECTs goes to the bit bucket */
  dest = CreateDestReceiver(DestNone);

  /*
   * Do parse analysis, rule rewrite, planning, and execution for each raw
   * parsetree.  We must fully execute each query before beginning parse
   * analysis on the next one, since there may be interdependencies.
   */
  foreach(lc1, raw_parsetree_list)
  {
    RawStmt    *parsetree = lfirst_node(RawStmt, lc1);
    MemoryContext per_parsetree_context,
          oldcontext;
    List     *stmt_list;
    ListCell   *lc2;

    /* Report location of this query for error context callback */
    callback_arg.stmt_location = parsetree->stmt_location;
    callback_arg.stmt_len = parsetree->stmt_len;

    /*
     * We do the work for each parsetree in a short-lived context, to
     * limit the memory used when there are many commands in the string.
     */
    per_parsetree_context =
      AllocSetContextCreate(CurrentMemoryContext,
                  "execute_sql_string per-statement context",
                  ALLOCSET_DEFAULT_SIZES);
    oldcontext = MemoryContextSwitchTo(per_parsetree_context);

    /* Be sure parser can see any DDL done so far */
    CommandCounterIncrement();

    stmt_list = pg_analyze_and_rewrite_fixedparams(parsetree,
                             sql,
                             NULL,
                             0,
                             NULL);
    stmt_list = pg_plan_queries(stmt_list, sql, CURSOR_OPT_PARALLEL_OK, NULL);

    foreach(lc2, stmt_list)
    {
      PlannedStmt *stmt = lfirst_node(PlannedStmt, lc2);

      CommandCounterIncrement();

      PushActiveSnapshot(GetTransactionSnapshot());

      if (stmt->utilityStmt == NULL)
      {
        QueryDesc  *qdesc;

        qdesc = CreateQueryDesc(stmt,
                    sql,
                    GetActiveSnapshot(), NULL,
                    dest, NULL, NULL, 0);

        ExecutorStart(qdesc, 0);
        ExecutorRun(qdesc, ForwardScanDirection, 0);
        ExecutorFinish(qdesc);
        ExecutorEnd(qdesc);

        FreeQueryDesc(qdesc);
      }
      else
      {
        if (IsA(stmt->utilityStmt, TransactionStmt))
          ereport(ERROR,
              (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
               errmsg("transaction control statements are not allowed within an extension script")));

        ProcessUtility(stmt,
                 sql,
                 false,
                 PROCESS_UTILITY_QUERY,
                 NULL,
                 NULL,
                 dest,
                 NULL);
      }

      PopActiveSnapshot();
    }

    /* Clean up per-parsetree context. */
    MemoryContextSwitchTo(oldcontext);
    MemoryContextDelete(per_parsetree_context);
  }

  error_context_stack = scripterrcontext.previous;

  /* Be sure to advance the command counter after the last script command */
  CommandCounterIncrement();
}

/*
 * Policy function: is the given extension trusted for installation by a
 * non-superuser?
 *
 * (Update the errhint logic below if you change this.)
 */
static bool
extension_is_trusted(ExtensionControlFile *control)
{
  AclResult aclresult;

  /* Never trust unless extension's control file says it's okay */
  if (!control->trusted)
    return false;
  /* Allow if user has CREATE privilege on current database */
  aclresult = object_aclcheck(DatabaseRelationId, MyDatabaseId, GetUserId(), ACL_CREATE);
  if (aclresult == ACLCHECK_OK)
    return true;
  return false;
}

/*
 * Execute the appropriate script file for installing or updating the extension
 *
 * If from_version isn't NULL, it's an update
 *
 * Note: requiredSchemas must be one-for-one with the control->requires list
 */
static void
execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
             const char *from_version,
             const char *version,
             List *requiredSchemas,
             const char *schemaName)
{
  bool    switch_to_superuser = false;
  char     *filename;
  Oid     save_userid = 0;
  int     save_sec_context = 0;
  int     save_nestlevel;
  StringInfoData pathbuf;
  ListCell   *lc;
  ListCell   *lc2;

  /*
   * Enforce superuser-ness if appropriate.  We postpone these checks until
   * here so that the control flags are correctly associated with the right
   * script(s) if they happen to be set in secondary control files.
   */
  if (control->superuser && !superuser())
  {
    if (extension_is_trusted(control))
      switch_to_superuser = true;
    else if (from_version == NULL)
      ereport(ERROR,
          (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
           errmsg("permission denied to create extension \"%s\"",
              control->name),
           control->trusted
           ? errhint("Must have CREATE privilege on current database to create this extension.")
           : errhint("Must be superuser to create this extension.")));
    else
      ereport(ERROR,
          (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
           errmsg("permission denied to update extension \"%s\"",
              control->name),
           control->trusted
           ? errhint("Must have CREATE privilege on current database to update this extension.")
           : errhint("Must be superuser to update this extension.")));
  }

  filename = get_extension_script_filename(control, from_version, version);

  if (from_version == NULL)
    elog(DEBUG1, "executing extension script for \"%s\" version '%s'", control->name, version);
  else
    elog(DEBUG1, "executing extension script for \"%s\" update from version '%s' to '%s'", control->name, from_version, version);

  /*
   * If installing a trusted extension on behalf of a non-superuser, become
   * the bootstrap superuser.  (This switch will be cleaned up automatically
   * if the transaction aborts, as will the GUC changes below.)
   */
  if (switch_to_superuser)
  {
    GetUserIdAndSecContext(&save_userid, &save_sec_context);
    SetUserIdAndSecContext(BOOTSTRAP_SUPERUSERID,
                 save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
  }

  /*
   * Force client_min_messages and log_min_messages to be at least WARNING,
   * so that we won't spam the user with useless NOTICE messages from common
   * script actions like creating shell types.
   *
   * We use the equivalent of a function SET option to allow the setting to
   * persist for exactly the duration of the script execution.  guc.c also
   * takes care of undoing the setting on error.
   *
   * log_min_messages can't be set by ordinary users, so for that one we
   * pretend to be superuser.
   */
  save_nestlevel = NewGUCNestLevel();

  if (client_min_messages < WARNING)
    (void) set_config_option("client_min_messages", "warning",
                 PGC_USERSET, PGC_S_SESSION,
                 GUC_ACTION_SAVE, true, 0, false);
  if (log_min_messages < WARNING)
    (void) set_config_option_ext("log_min_messages", "warning",
                   PGC_SUSET, PGC_S_SESSION,
                   BOOTSTRAP_SUPERUSERID,
                   GUC_ACTION_SAVE, true, 0, false);

  /*
   * Similarly disable check_function_bodies, to ensure that SQL functions
   * won't be parsed during creation.
   */
  if (check_function_bodies)
    (void) set_config_option("check_function_bodies", "off",
                 PGC_USERSET, PGC_S_SESSION,
                 GUC_ACTION_SAVE, true, 0, false);

  /*
   * Set up the search path to have the target schema first, making it be
   * the default creation target namespace.  Then add the schemas of any
   * prerequisite extensions, unless they are in pg_catalog which would be
   * searched anyway.  (Listing pg_catalog explicitly in a non-first
   * position would be bad for security.)  Finally add pg_temp to ensure
   * that temp objects can't take precedence over others.
   */
  initStringInfo(&pathbuf);
  appendStringInfoString(&pathbuf, quote_identifier(schemaName));
  foreach(lc, requiredSchemas)
  {
    Oid     reqschema = lfirst_oid(lc);
    char     *reqname = get_namespace_name(reqschema);

    if (reqname && strcmp(reqname, "pg_catalog") != 0)
      appendStringInfo(&pathbuf, ", %s", quote_identifier(reqname));
  }
  appendStringInfoString(&pathbuf, ", pg_temp");

  (void) set_config_option("search_path", pathbuf.data,
               PGC_USERSET, PGC_S_SESSION,
               GUC_ACTION_SAVE, true, 0, false);

  /*
   * Set creating_extension and related variables so that
   * recordDependencyOnCurrentExtension and other functions do the right
   * things.  On failure, ensure we reset these variables.
   */
  creating_extension = true;
  CurrentExtensionObject = extensionOid;
  PG_TRY();
  {
    char     *c_sql = read_extension_script_file(control, filename);
    Datum   t_sql;

    /*
     * We filter each substitution through quote_identifier().  When the
     * arg contains one of the following characters, no one collection of
     * quoting can work inside $$dollar-quoted string literals$$,
     * 'single-quoted string literals', and outside of any literal.  To
     * avoid a security snare for extension authors, error on substitution
     * for arguments containing these.
     */
    const char *quoting_relevant_chars = "\"$'\\";

    /* We use various functions that want to operate on text datums */
    t_sql = CStringGetTextDatum(c_sql);

    /*
     * Reduce any lines beginning with "\echo" to empty.  This allows
     * scripts to contain messages telling people not to run them via
     * psql, which has been found to be necessary due to old habits.
     */
    t_sql = DirectFunctionCall4Coll(textregexreplace,
                    C_COLLATION_OID,
                    t_sql,
                    CStringGetTextDatum("^\\\\echo.*$"),
                    CStringGetTextDatum(""),
                    CStringGetTextDatum("ng"));

    /*
     * If the script uses @extowner@, substitute the calling username.
     */
    if (strstr(c_sql, "@extowner@"))
    {
      Oid     uid = switch_to_superuser ? save_userid : GetUserId();
      const char *userName = GetUserNameFromId(uid, false);
      const char *qUserName = quote_identifier(userName);

      t_sql = DirectFunctionCall3Coll(replace_text,
                      C_COLLATION_OID,
                      t_sql,
                      CStringGetTextDatum("@extowner@"),
                      CStringGetTextDatum(qUserName));
      if (strpbrk(userName, quoting_relevant_chars))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
             errmsg("invalid character in extension owner: must not contain any of \"%s\"",
                quoting_relevant_chars)));
    }

    /*
     * If it's not relocatable, substitute the target schema name for
     * occurrences of @extschema@.
     *
     * For a relocatable extension, we needn't do this.  There cannot be
     * any need for @extschema@, else it wouldn't be relocatable.
     */
    if (!control->relocatable)
    {
      Datum   old = t_sql;
      const char *qSchemaName = quote_identifier(schemaName);

      t_sql = DirectFunctionCall3Coll(replace_text,
                      C_COLLATION_OID,
                      t_sql,
                      CStringGetTextDatum("@extschema@"),
                      CStringGetTextDatum(qSchemaName));
      if (t_sql != old && strpbrk(schemaName, quoting_relevant_chars))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
             errmsg("invalid character in extension \"%s\" schema: must not contain any of \"%s\"",
                control->name, quoting_relevant_chars)));
    }

    /*
     * Likewise, substitute required extensions' schema names for
     * occurrences of @extschema:extension_name@.
     */
    Assert(list_length(control->requires) == list_length(requiredSchemas));
    forboth(lc, control->requires, lc2, requiredSchemas)
    {
      Datum   old = t_sql;
      char     *reqextname = (char *) lfirst(lc);
      Oid     reqschema = lfirst_oid(lc2);
      char     *schemaName = get_namespace_name(reqschema);
      const char *qSchemaName = quote_identifier(schemaName);
      char     *repltoken;

      repltoken = psprintf("@extschema:%s@", reqextname);
      t_sql = DirectFunctionCall3Coll(replace_text,
                      C_COLLATION_OID,
                      t_sql,
                      CStringGetTextDatum(repltoken),
                      CStringGetTextDatum(qSchemaName));
      if (t_sql != old && strpbrk(schemaName, quoting_relevant_chars))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
             errmsg("invalid character in extension \"%s\" schema: must not contain any of \"%s\"",
                reqextname, quoting_relevant_chars)));
    }

    /*
     * If module_pathname was set in the control file, substitute its
     * value for occurrences of MODULE_PATHNAME.
     */
    if (control->module_pathname)
    {
      t_sql = DirectFunctionCall3Coll(replace_text,
                      C_COLLATION_OID,
                      t_sql,
                      CStringGetTextDatum("MODULE_PATHNAME"),
                      CStringGetTextDatum(control->module_pathname));
    }

    /* And now back to C string */
    c_sql = text_to_cstring(DatumGetTextPP(t_sql));

    execute_sql_string(c_sql, filename);
  }
  PG_FINALLY();
  {
    creating_extension = false;
    CurrentExtensionObject = InvalidOid;
  }
  PG_END_TRY();

  /*
   * Restore the GUC variables we set above.
   */
  AtEOXact_GUC(true, save_nestlevel);

  /*
   * Restore authentication state if needed.
   */
  if (switch_to_superuser)
    SetUserIdAndSecContext(save_userid, save_sec_context);
}

/*
 * Find or create an ExtensionVersionInfo for the specified version name
 *
 * Currently, we just use a List of the ExtensionVersionInfo's.  Searching
 * for them therefore uses about O(N^2) time when there are N versions of
 * the extension.  We could change the data structure to a hash table if
 * this ever becomes a bottleneck.
 */
static ExtensionVersionInfo *
get_ext_ver_info(const char *versionname, List **evi_list)
{
  ExtensionVersionInfo *evi;
  ListCell   *lc;

  foreach(lc, *evi_list)
  {
    evi = (ExtensionVersionInfo *) lfirst(lc);
    if (strcmp(evi->name, versionname) == 0)
      return evi;
  }

  evi = (ExtensionVersionInfo *) palloc(sizeof(ExtensionVersionInfo));
  evi->name = pstrdup(versionname);
  evi->reachable = NIL;
  evi->installable = false;
  /* initialize for later application of Dijkstra's algorithm */
  evi->distance_known = false;
  evi->distance = INT_MAX;
  evi->previous = NULL;

  *evi_list = lappend(*evi_list, evi);

  return evi;
}

/*
 * Locate the nearest unprocessed ExtensionVersionInfo
 *
 * This part of the algorithm is also about O(N^2).  A priority queue would
 * make it much faster, but for now there's no need.
 */
static ExtensionVersionInfo *
get_nearest_unprocessed_vertex(List *evi_list)
{
  ExtensionVersionInfo *evi = NULL;
  ListCell   *lc;

  foreach(lc, evi_list)
  {
    ExtensionVersionInfo *evi2 = (ExtensionVersionInfo *) lfirst(lc);

    /* only vertices whose distance is still uncertain are candidates */
    if (evi2->distance_known)
      continue;
    /* remember the closest such vertex */
    if (evi == NULL ||
      evi->distance > evi2->distance)
      evi = evi2;
  }

  return evi;
}

/*
 * Obtain information about the set of update scripts available for the
 * specified extension.  The result is a List of ExtensionVersionInfo
 * structs, each with a subsidiary list of the ExtensionVersionInfos for
 * the versions that can be reached in one step from that version.
 */
static List *
get_ext_ver_list(ExtensionControlFile *control)
{
  List     *evi_list = NIL;
  int     extnamelen = strlen(control->name);
  char     *location;
  DIR      *dir;
  struct dirent *de;

  location = get_extension_script_directory(control);
  dir = AllocateDir(location);
  while ((de = ReadDir(dir, location)) != NULL)
  {
    char     *vername;
    char     *vername2;
    ExtensionVersionInfo *evi;
    ExtensionVersionInfo *evi2;

    /* must be a .sql file ... */
    if (!is_extension_script_filename(de->d_name))
      continue;

    /* ... matching extension name followed by separator */
    if (strncmp(de->d_name, control->name, extnamelen) != 0 ||
      de->d_name[extnamelen] != '-' ||
      de->d_name[extnamelen + 1] != '-')
      continue;

    /* extract version name(s) from 'extname--something.sql' filename */
    vername = pstrdup(de->d_name + extnamelen + 2);
    *strrchr(vername, '.') = '\0';
    vername2 = strstr(vername, "--");
    if (!vername2)
    {
      /* It's an install, not update, script; record its version name */
      evi = get_ext_ver_info(vername, &evi_list);
      evi->installable = true;
      continue;
    }
    *vername2 = '\0';   /* terminate first version */
    vername2 += 2;      /* and point to second */

    /* if there's a third --, it's bogus, ignore it */
    if (strstr(vername2, "--"))
      continue;

    /* Create ExtensionVersionInfos and link them together */
    evi = get_ext_ver_info(vername, &evi_list);
    evi2 = get_ext_ver_info(vername2, &evi_list);
    evi->reachable = lappend(evi->reachable, evi2);
  }
  FreeDir(dir);

  return evi_list;
}

/*
 * Given an initial and final version name, identify the sequence of update
 * scripts that have to be applied to perform that update.
 *
 * Result is a List of names of versions to transition through (the initial
 * version is *not* included).
 */
static List *
identify_update_path(ExtensionControlFile *control,
           const char *oldVersion, const char *newVersion)
{
  List     *result;
  List     *evi_list;
  ExtensionVersionInfo *evi_start;
  ExtensionVersionInfo *evi_target;

  /* Extract the version update graph from the script directory */
  evi_list = get_ext_ver_list(control);

  /* Initialize start and end vertices */
  evi_start = get_ext_ver_info(oldVersion, &evi_list);
  evi_target = get_ext_ver_info(newVersion, &evi_list);

  /* Find shortest path */
  result = find_update_path(evi_list, evi_start, evi_target, false, false);

  if (result == NIL)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("extension \"%s\" has no update path from version \"%s\" to version \"%s\"",
            control->name, oldVersion, newVersion)));

  return result;
}

/*
 * Apply Dijkstra's algorithm to find the shortest path from evi_start to
 * evi_target.
 *
 * If reject_indirect is true, ignore paths that go through installable
 * versions.  This saves work when the caller will consider starting from
 * all installable versions anyway.
 *
 * If reinitialize is false, assume the ExtensionVersionInfo list has not
 * been used for this before, and the initialization done by get_ext_ver_info
 * is still good.  Otherwise, reinitialize all transient fields used here.
 *
 * Result is a List of names of versions to transition through (the initial
 * version is *not* included).  Returns NIL if no such path.
 */
static List *
find_update_path(List *evi_list,
         ExtensionVersionInfo *evi_start,
         ExtensionVersionInfo *evi_target,
         bool reject_indirect,
         bool reinitialize)
{
  List     *result;
  ExtensionVersionInfo *evi;
  ListCell   *lc;

  /* Caller error if start == target */
  Assert(evi_start != evi_target);
  /* Caller error if reject_indirect and target is installable */
  Assert(!(reject_indirect && evi_target->installable));

  if (reinitialize)
  {
    foreach(lc, evi_list)
    {
      evi = (ExtensionVersionInfo *) lfirst(lc);
      evi->distance_known = false;
      evi->distance = INT_MAX;
      evi->previous = NULL;
    }
  }

  evi_start->distance = 0;

  while ((evi = get_nearest_unprocessed_vertex(evi_list)) != NULL)
  {
    if (evi->distance == INT_MAX)
      break;       /* all remaining vertices are unreachable */
    evi->distance_known = true;
    if (evi == evi_target)
      break;       /* found shortest path to target */
    foreach(lc, evi->reachable)
    {
      ExtensionVersionInfo *evi2 = (ExtensionVersionInfo *) lfirst(lc);
      int     newdist;

      /* if reject_indirect, treat installable versions as unreachable */
      if (reject_indirect && evi2->installable)
        continue;
      newdist = evi->distance + 1;
      if (newdist < evi2->distance)
      {
        evi2->distance = newdist;
        evi2->previous = evi;
      }
      else if (newdist == evi2->distance &&
           evi2->previous != NULL &&
           strcmp(evi->name, evi2->previous->name) < 0)
      {
        /*
         * Break ties in favor of the version name that comes first
         * according to strcmp().  This behavior is undocumented and
         * users shouldn't rely on it.  We do it just to ensure that
         * if there is a tie, the update path that is chosen does not
         * depend on random factors like the order in which directory
         * entries get visited.
         */
        evi2->previous = evi;
      }
    }
  }

  /* Return NIL if target is not reachable from start */
  if (!evi_target->distance_known)
    return NIL;

  /* Build and return list of version names representing the update path */
  result = NIL;
  for (evi = evi_target; evi != evi_start; evi = evi->previous)
    result = lcons(evi->name, result);

  return result;
}

/*
 * Given a target version that is not directly installable, find the
 * best installation sequence starting from a directly-installable version.
 *
 * evi_list: previously-collected version update graph
 * evi_target: member of that list that we want to reach
 *
 * Returns the best starting-point version, or NULL if there is none.
 * On success, *best_path is set to the path from the start point.
 *
 * If there's more than one possible start point, prefer shorter update paths,
 * and break any ties arbitrarily on the basis of strcmp'ing the starting
 * versions' names.
 */
static ExtensionVersionInfo *
find_install_path(List *evi_list, ExtensionVersionInfo *evi_target,
          List **best_path)
{
  ExtensionVersionInfo *evi_start = NULL;
  ListCell   *lc;

  *best_path = NIL;

  /*
   * We don't expect to be called for an installable target, but if we are,
   * the answer is easy: just start from there, with an empty update path.
   */
  if (evi_target->installable)
    return evi_target;

  /* Consider all installable versions as start points */
  foreach(lc, evi_list)
  {
    ExtensionVersionInfo *evi1 = (ExtensionVersionInfo *) lfirst(lc);
    List     *path;

    if (!evi1->installable)
      continue;

    /*
     * Find shortest path from evi1 to evi_target; but no need to consider
     * paths going through other installable versions.
     */
    path = find_update_path(evi_list, evi1, evi_target, true, true);
    if (path == NIL)
      continue;

    /* Remember best path */
    if (evi_start == NULL ||
      list_length(path) < list_length(*best_path) ||
      (list_length(path) == list_length(*best_path) &&
       strcmp(evi_start->name, evi1->name) < 0))
    {
      evi_start = evi1;
      *best_path = path;
    }
  }

  return evi_start;
}

/*
 * CREATE EXTENSION worker
 *
 * When CASCADE is specified, CreateExtensionInternal() recurses if required
 * extensions need to be installed.  To sanely handle cyclic dependencies,
 * the "parents" list contains a list of names of extensions already being
 * installed, allowing us to error out if we recurse to one of those.
 */
static ObjectAddress
CreateExtensionInternal(char *extensionName,
            char *schemaName,
            const char *versionName,
            bool cascade,
            List *parents,
            bool is_create)
{
  char     *origSchemaName = schemaName;
  Oid     schemaOid = InvalidOid;
  Oid     extowner = GetUserId();
  ExtensionControlFile *pcontrol;
  ExtensionControlFile *control;
  char     *filename;
  struct stat fst;
  List     *updateVersions;
  List     *requiredExtensions;
  List     *requiredSchemas;
  Oid     extensionOid;
  ObjectAddress address;
  ListCell   *lc;

  /*
   * Read the primary control file.  Note we assume that it does not contain
   * any non-ASCII data, so there is no need to worry about encoding at this
   * point.
   */
  pcontrol = read_extension_control_file(extensionName);

  /*
   * Determine the version to install
   */
  if (versionName == NULL)
  {
    if (pcontrol->default_version)
      versionName = pcontrol->default_version;
    else
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
           errmsg("version to install must be specified")));
  }
  check_valid_version_name(versionName);

  /*
   * Figure out which script(s) we need to run to install the desired
   * version of the extension.  If we do not have a script that directly
   * does what is needed, we try to find a sequence of update scripts that
   * will get us there.
   */
  filename = get_extension_script_filename(pcontrol, NULL, versionName);
  if (stat(filename, &fst) == 0)
  {
    /* Easy, no extra scripts */
    updateVersions = NIL;
  }
  else
  {
    /* Look for best way to install this version */
    List     *evi_list;
    ExtensionVersionInfo *evi_start;
    ExtensionVersionInfo *evi_target;

    /* Extract the version update graph from the script directory */
    evi_list = get_ext_ver_list(pcontrol);

    /* Identify the target version */
    evi_target = get_ext_ver_info(versionName, &evi_list);

    /* Identify best path to reach target */
    evi_start = find_install_path(evi_list, evi_target,
                    &updateVersions);

    /* Fail if no path ... */
    if (evi_start == NULL)
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
           errmsg("extension \"%s\" has no installation script nor update path for version \"%s\"",
              pcontrol->name, versionName)));

    /* Otherwise, install best starting point and then upgrade */
    versionName = evi_start->name;
  }

  /*
   * Fetch control parameters for installation target version
   */
  control = read_extension_aux_control_file(pcontrol, versionName);

  /*
   * Determine the target schema to install the extension into
   */
  if (schemaName)
  {
    /* If the user is giving us the schema name, it must exist already. */
    schemaOid = get_namespace_oid(schemaName, false);
  }

  if (control->schema != NULL)
  {
    /*
     * The extension is not relocatable and the author gave us a schema
     * for it.
     *
     * Unless CASCADE parameter was given, it's an error to give a schema
     * different from control->schema if control->schema is specified.
     */
    if (schemaName && strcmp(control->schema, schemaName) != 0 &&
      !cascade)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("extension \"%s\" must be installed in schema \"%s\"",
              control->name,
              control->schema)));

    /* Always use the schema from control file for current extension. */
    schemaName = control->schema;

    /* Find or create the schema in case it does not exist. */
    schemaOid = get_namespace_oid(schemaName, true);

    if (!OidIsValid(schemaOid))
    {
      CreateSchemaStmt *csstmt = makeNode(CreateSchemaStmt);

      csstmt->schemaname = schemaName;
      csstmt->authrole = NULL;  /* will be created by current user */
      csstmt->schemaElts = NIL;
      csstmt->if_not_exists = false;
      CreateSchemaCommand(csstmt, "(generated CREATE SCHEMA command)",
                -1, -1);

      /*
       * CreateSchemaCommand includes CommandCounterIncrement, so new
       * schema is now visible.
       */
      schemaOid = get_namespace_oid(schemaName, false);
    }
  }
  else if (!OidIsValid(schemaOid))
  {
    /*
     * Neither user nor author of the extension specified schema; use the
     * current default creation namespace, which is the first explicit
     * entry in the search_path.
     */
    List     *search_path = fetch_search_path(false);

    if (search_path == NIL) /* nothing valid in search_path? */
      ereport(ERROR,
          (errcode(ERRCODE_UNDEFINED_SCHEMA),
           errmsg("no schema has been selected to create in")));
    schemaOid = linitial_oid(search_path);
    schemaName = get_namespace_name(schemaOid);
    if (schemaName == NULL) /* recently-deleted namespace? */
      ereport(ERROR,
          (errcode(ERRCODE_UNDEFINED_SCHEMA),
           errmsg("no schema has been selected to create in")));

    list_free(search_path);
  }

  /*
   * Make note if a temporary namespace has been accessed in this
   * transaction.
   */
  if (isTempNamespace(schemaOid))
    MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPNAMESPACE;

  /*
   * We don't check creation rights on the target namespace here.  If the
   * extension script actually creates any objects there, it will fail if
   * the user doesn't have such permissions.  But there are cases such as
   * procedural languages where it's convenient to set schema = pg_catalog
   * yet we don't want to restrict the command to users with ACL_CREATE for
   * pg_catalog.
   */

  /*
   * Look up the prerequisite extensions, install them if necessary, and
   * build lists of their OIDs and the OIDs of their target schemas.
   */
  requiredExtensions = NIL;
  requiredSchemas = NIL;
  foreach(lc, control->requires)
  {
    char     *curreq = (char *) lfirst(lc);
    Oid     reqext;
    Oid     reqschema;

    reqext = get_required_extension(curreq,
                    extensionName,
                    origSchemaName,
                    cascade,
                    parents,
                    is_create);
    reqschema = get_extension_schema(reqext);
    requiredExtensions = lappend_oid(requiredExtensions, reqext);
    requiredSchemas = lappend_oid(requiredSchemas, reqschema);
  }

  /*
   * Insert new tuple into pg_extension, and create dependency entries.
   */
  address = InsertExtensionTuple(control->name, extowner,
                   schemaOid, control->relocatable,
                   versionName,
                   PointerGetDatum(NULL),
                   PointerGetDatum(NULL),
                   requiredExtensions);
  extensionOid = address.objectId;

  /*
   * Apply any control-file comment on extension
   */
  if (control->comment != NULL)
    CreateComments(extensionOid, ExtensionRelationId, 0, control->comment);

  /*
   * Execute the installation script file
   */
  execute_extension_script(extensionOid, control,
               NULL, versionName,
               requiredSchemas,
               schemaName);

  /*
   * If additional update scripts have to be executed, apply the updates as
   * though a series of ALTER EXTENSION UPDATE commands were given
   */
  ApplyExtensionUpdates(extensionOid, pcontrol,
              versionName, updateVersions,
              origSchemaName, cascade, is_create);

  return address;
}

/*
 * Get the OID of an extension listed in "requires", possibly creating it.
 */
static Oid
get_required_extension(char *reqExtensionName,
             char *extensionName,
             char *origSchemaName,
             bool cascade,
             List *parents,
             bool is_create)
{
  Oid     reqExtensionOid;

  reqExtensionOid = get_extension_oid(reqExtensionName, true);
  if (!OidIsValid(reqExtensionOid))
  {
    if (cascade)
    {
      /* Must install it. */
      ObjectAddress addr;
      List     *cascade_parents;
      ListCell   *lc;

      /* Check extension name validity before trying to cascade. */
      check_valid_extension_name(reqExtensionName);

      /* Check for cyclic dependency between extensions. */
      foreach(lc, parents)
      {
        char     *pname = (char *) lfirst(lc);

        if (strcmp(pname, reqExtensionName) == 0)
          ereport(ERROR,
              (errcode(ERRCODE_INVALID_RECURSION),
               errmsg("cyclic dependency detected between extensions \"%s\" and \"%s\"",
                  reqExtensionName, extensionName)));
      }

      ereport(NOTICE,
          (errmsg("installing required extension \"%s\"",
              reqExtensionName)));

      /* Add current extension to list of parents to pass down. */
      cascade_parents = lappend(list_copy(parents), extensionName);

      /*
       * Create the required extension.  We propagate the SCHEMA option
       * if any, and CASCADE, but no other options.
       */
      addr = CreateExtensionInternal(reqExtensionName,
                       origSchemaName,
                       NULL,
                       cascade,
                       cascade_parents,
                       is_create);

      /* Get its newly-assigned OID. */
      reqExtensionOid = addr.objectId;
    }
    else
      ereport(ERROR,
          (errcode(ERRCODE_UNDEFINED_OBJECT),
           errmsg("required extension \"%s\" is not installed",
              reqExtensionName),
           is_create ?
           errhint("Use CREATE EXTENSION ... CASCADE to install required extensions too.") : 0));
  }

  return reqExtensionOid;
}

/*
 * CREATE EXTENSION
 */
ObjectAddress
CreateExtension(ParseState *pstate, CreateExtensionStmt *stmt)
{
  DefElem    *d_schema = NULL;
  DefElem    *d_new_version = NULL;
  DefElem    *d_cascade = NULL;
  char     *schemaName = NULL;
  char     *versionName = NULL;
  bool    cascade = false;
  ListCell   *lc;

  /* Check extension name validity before any filesystem access */
  check_valid_extension_name(stmt->extname);

  /*
   * Check for duplicate extension name.  The unique index on
   * pg_extension.extname would catch this anyway, and serves as a backstop
   * in case of race conditions; but this is a friendlier error message, and
   * besides we need a check to support IF NOT EXISTS.
   */
  if (get_extension_oid(stmt->extname, true) != InvalidOid)
  {
    if (stmt->if_not_exists)
    {
      ereport(NOTICE,
          (errcode(ERRCODE_DUPLICATE_OBJECT),
           errmsg("extension \"%s\" already exists, skipping",
              stmt->extname)));
      return InvalidObjectAddress;
    }
    else
      ereport(ERROR,
          (errcode(ERRCODE_DUPLICATE_OBJECT),
           errmsg("extension \"%s\" already exists",
              stmt->extname)));
  }

  /*
   * We use global variables to track the extension being created, so we can
   * create only one extension at the same time.
   */
  if (creating_extension)
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("nested CREATE EXTENSION is not supported")));

  /* Deconstruct the statement option list */
  foreach(lc, stmt->options)
  {
    DefElem    *defel = (DefElem *) lfirst(lc);

    if (strcmp(defel->defname, "schema") == 0)
    {
      if (d_schema)
        errorConflictingDefElem(defel, pstate);
      d_schema = defel;
      schemaName = defGetString(d_schema);
    }
    else if (strcmp(defel->defname, "new_version") == 0)
    {
      if (d_new_version)
        errorConflictingDefElem(defel, pstate);
      d_new_version = defel;
      versionName = defGetString(d_new_version);
    }
    else if (strcmp(defel->defname, "cascade") == 0)
    {
      if (d_cascade)
        errorConflictingDefElem(defel, pstate);
      d_cascade = defel;
      cascade = defGetBoolean(d_cascade);
    }
    else
      elog(ERROR, "unrecognized option: %s", defel->defname);
  }

  /* Call CreateExtensionInternal to do the real work. */
  return CreateExtensionInternal(stmt->extname,
                   schemaName,
                   versionName,
                   cascade,
                   NIL,
                   true);
}

/*
 * InsertExtensionTuple
 *
 * Insert the new pg_extension row, and create extension's dependency entries.
 * Return the OID assigned to the new row.
 *
 * This is exported for the benefit of pg_upgrade, which has to create a
 * pg_extension entry (and the extension-level dependencies) without
 * actually running the extension's script.
 *
 * extConfig and extCondition should be arrays or PointerGetDatum(NULL).
 * We declare them as plain Datum to avoid needing array.h in extension.h.
 */
ObjectAddress
InsertExtensionTuple(const char *extName, Oid extOwner,
           Oid schemaOid, bool relocatable, const char *extVersion,
           Datum extConfig, Datum extCondition,
           List *requiredExtensions)
{
  Oid     extensionOid;
  Relation  rel;
  Datum   values[Natts_pg_extension];
  bool    nulls[Natts_pg_extension];
  HeapTuple tuple;
  ObjectAddress myself;
  ObjectAddress nsp;
  ObjectAddresses *refobjs;
  ListCell   *lc;

  /*
   * Build and insert the pg_extension tuple
   */
  rel = table_open(ExtensionRelationId, RowExclusiveLock);

  memset(values, 0, sizeof(values));
  memset(nulls, 0, sizeof(nulls));

  extensionOid = GetNewOidWithIndex(rel, ExtensionOidIndexId,
                    Anum_pg_extension_oid);
  values[Anum_pg_extension_oid - 1] = ObjectIdGetDatum(extensionOid);
  values[Anum_pg_extension_extname - 1] =
    DirectFunctionCall1(namein, CStringGetDatum(extName));
  values[Anum_pg_extension_extowner - 1] = ObjectIdGetDatum(extOwner);
  values[Anum_pg_extension_extnamespace - 1] = ObjectIdGetDatum(schemaOid);
  values[Anum_pg_extension_extrelocatable - 1] = BoolGetDatum(relocatable);
  values[Anum_pg_extension_extversion - 1] = CStringGetTextDatum(extVersion);

  if (extConfig == PointerGetDatum(NULL))
    nulls[Anum_pg_extension_extconfig - 1] = true;
  else
    values[Anum_pg_extension_extconfig - 1] = extConfig;

  if (extCondition == PointerGetDatum(NULL))
    nulls[Anum_pg_extension_extcondition - 1] = true;
  else
    values[Anum_pg_extension_extcondition - 1] = extCondition;

  tuple = heap_form_tuple(rel->rd_att, values, nulls);

  CatalogTupleInsert(rel, tuple);

  heap_freetuple(tuple);
  table_close(rel, RowExclusiveLock);

  /*
   * Record dependencies on owner, schema, and prerequisite extensions
   */
  recordDependencyOnOwner(ExtensionRelationId, extensionOid, extOwner);

  refobjs = new_object_addresses();

  ObjectAddressSet(myself, ExtensionRelationId, extensionOid);

  ObjectAddressSet(nsp, NamespaceRelationId, schemaOid);
  add_exact_object_address(&nsp, refobjs);

  foreach(lc, requiredExtensions)
  {
    Oid     reqext = lfirst_oid(lc);
    ObjectAddress otherext;

    ObjectAddressSet(otherext, ExtensionRelationId, reqext);
    add_exact_object_address(&otherext, refobjs);
  }

  /* Record all of them (this includes duplicate elimination) */
  record_object_address_dependencies(&myself, refobjs, DEPENDENCY_NORMAL);
  free_object_addresses(refobjs);

  /* Post creation hook for new extension */
  InvokeObjectPostCreateHook(ExtensionRelationId, extensionOid, 0);

  return myself;
}

/*
 * Guts of extension deletion.
 *
 * All we need do here is remove the pg_extension tuple itself.  Everything
 * else is taken care of by the dependency infrastructure.
 */
void
RemoveExtensionById(Oid extId)
{
  Relation  rel;
  SysScanDesc scandesc;
  HeapTuple tuple;
  ScanKeyData entry[1];

  /*
   * Disallow deletion of any extension that's currently open for insertion;
   * else subsequent executions of recordDependencyOnCurrentExtension()
   * could create dangling pg_depend records that refer to a no-longer-valid
   * pg_extension OID.  This is needed not so much because we think people
   * might write "DROP EXTENSION foo" in foo's own script files, as because
   * errors in dependency management in extension script files could give
   * rise to cases where an extension is dropped as a result of recursing
   * from some contained object.  Because of that, we must test for the case
   * here, not at some higher level of the DROP EXTENSION command.
   */
  if (extId == CurrentExtensionObject)
    ereport(ERROR,
        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
         errmsg("cannot drop extension \"%s\" because it is being modified",
            get_extension_name(extId))));

  rel = table_open(ExtensionRelationId, RowExclusiveLock);

  ScanKeyInit(&entry[0],
        Anum_pg_extension_oid,
        BTEqualStrategyNumber, F_OIDEQ,
        ObjectIdGetDatum(extId));
  scandesc = systable_beginscan(rel, ExtensionOidIndexId, true,
                  NULL, 1, entry);

  tuple = systable_getnext(scandesc);

  /* We assume that there can be at most one matching tuple */
  if (HeapTupleIsValid(tuple))
    CatalogTupleDelete(rel, &tuple->t_self);

  systable_endscan(scandesc);

  table_close(rel, RowExclusiveLock);
}

/*
 * This function lists the available extensions (one row per primary control
 * file in the control directory).  We parse each control file and report the
 * interesting fields.
 *
 * The system view pg_available_extensions provides a user interface to this
 * SRF, adding information about whether the extensions are installed in the
 * current DB.
 */
Datum
pg_available_extensions(PG_FUNCTION_ARGS)
{
  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
  List     *locations;
  DIR      *dir;
  struct dirent *de;

  /* Build tuplestore to hold the result rows */
  InitMaterializedSRF(fcinfo, 0);

  locations = get_extension_control_directories();

  foreach_ptr(char, location, locations)
  {
    dir = AllocateDir(location);

    /*
     * If the control directory doesn't exist, we want to silently return
     * an empty set.  Any other error will be reported by ReadDir.
     */
    if (dir == NULL && errno == ENOENT)
    {
      /* do nothing */
    }
    else
    {
      while ((de = ReadDir(dir, location)) != NULL)
      {
        ExtensionControlFile *control;
        char     *extname;
        Datum   values[3];
        bool    nulls[3];

        if (!is_extension_control_filename(de->d_name))
          continue;

        /* extract extension name from 'name.control' filename */
        extname = pstrdup(de->d_name);
        *strrchr(extname, '.') = '\0';

        /* ignore it if it's an auxiliary control file */
        if (strstr(extname, "--"))
          continue;

        control = new_ExtensionControlFile(extname);
        control->control_dir = pstrdup(location);
        parse_extension_control_file(control, NULL);

        memset(values, 0, sizeof(values));
        memset(nulls, 0, sizeof(nulls));

        /* name */
        values[0] = DirectFunctionCall1(namein,
                        CStringGetDatum(control->name));
        /* default_version */
        if (control->default_version == NULL)
          nulls[1] = true;
        else
          values[1] = CStringGetTextDatum(control->default_version);
        /* comment */
        if (control->comment == NULL)
          nulls[2] = true;
        else
          values[2] = CStringGetTextDatum(control->comment);

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

      FreeDir(dir);
    }
  }

  return (Datum) 0;
}

/*
 * This function lists the available extension versions (one row per
 * extension installation script).  For each version, we parse the related
 * control file(s) and report the interesting fields.
 *
 * The system view pg_available_extension_versions provides a user interface
 * to this SRF, adding information about which versions are installed in the
 * current DB.
 */
Datum
pg_available_extension_versions(PG_FUNCTION_ARGS)
{
  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
  List     *locations;
  DIR      *dir;
  struct dirent *de;

  /* Build tuplestore to hold the result rows */
  InitMaterializedSRF(fcinfo, 0);

  locations = get_extension_control_directories();

  foreach_ptr(char, location, locations)
  {
    dir = AllocateDir(location);

    /*
     * If the control directory doesn't exist, we want to silently return
     * an empty set.  Any other error will be reported by ReadDir.
     */
    if (dir == NULL && errno == ENOENT)
    {
      /* do nothing */
    }
    else
    {
      while ((de = ReadDir(dir, location)) != NULL)
      {
        ExtensionControlFile *control;
        char     *extname;

        if (!is_extension_control_filename(de->d_name))
          continue;

        /* extract extension name from 'name.control' filename */
        extname = pstrdup(de->d_name);
        *strrchr(extname, '.') = '\0';

        /* ignore it if it's an auxiliary control file */
        if (strstr(extname, "--"))
          continue;

        /* read the control file */
        control = new_ExtensionControlFile(extname);
        control->control_dir = pstrdup(location);
        parse_extension_control_file(control, NULL);

        /* scan extension's script directory for install scripts */
        get_available_versions_for_extension(control, rsinfo->setResult,
                           rsinfo->setDesc);
      }

      FreeDir(dir);
    }
  }

  return (Datum) 0;
}

/*
 * Inner loop for pg_available_extension_versions:
 *    read versions of one extension, add rows to tupstore
 */
static void
get_available_versions_for_extension(ExtensionControlFile *pcontrol,
                   Tuplestorestate *tupstore,
                   TupleDesc tupdesc)
{
  List     *evi_list;
  ListCell   *lc;

  /* Extract the version update graph from the script directory */
  evi_list = get_ext_ver_list(pcontrol);

  /* For each installable version ... */
  foreach(lc, evi_list)
  {
    ExtensionVersionInfo *evi = (ExtensionVersionInfo *) lfirst(lc);
    ExtensionControlFile *control;
    Datum   values[8];
    bool    nulls[8];
    ListCell   *lc2;

    if (!evi->installable)
      continue;

    /*
     * Fetch parameters for specific version (pcontrol is not changed)
     */
    control = read_extension_aux_control_file(pcontrol, evi->name);

    memset(values, 0, sizeof(values));
    memset(nulls, 0, sizeof(nulls));

    /* name */
    values[0] = DirectFunctionCall1(namein,
                    CStringGetDatum(control->name));
    /* version */
    values[1] = CStringGetTextDatum(evi->name);
    /* superuser */
    values[2] = BoolGetDatum(control->superuser);
    /* trusted */
    values[3] = BoolGetDatum(control->trusted);
    /* relocatable */
    values[4] = BoolGetDatum(control->relocatable);
    /* schema */
    if (control->schema == NULL)
      nulls[5] = true;
    else
      values[5] = DirectFunctionCall1(namein,
                      CStringGetDatum(control->schema));
    /* requires */
    if (control->requires == NIL)
      nulls[6] = true;
    else
      values[6] = convert_requires_to_datum(control->requires);
    /* comment */
    if (control->comment == NULL)
      nulls[7] = true;
    else
      values[7] = CStringGetTextDatum(control->comment);

    tuplestore_putvalues(tupstore, tupdesc, values, nulls);

    /*
     * Find all non-directly-installable versions that would be installed
     * starting from this version, and report them, inheriting the
     * parameters that aren't changed in updates from this version.
     */
    foreach(lc2, evi_list)
    {
      ExtensionVersionInfo *evi2 = (ExtensionVersionInfo *) lfirst(lc2);
      List     *best_path;

      if (evi2->installable)
        continue;
      if (find_install_path(evi_list, evi2, &best_path) == evi)
      {
        /*
         * Fetch parameters for this version (pcontrol is not changed)
         */
        control = read_extension_aux_control_file(pcontrol, evi2->name);

        /* name stays the same */
        /* version */
        values[1] = CStringGetTextDatum(evi2->name);
        /* superuser */
        values[2] = BoolGetDatum(control->superuser);
        /* trusted */
        values[3] = BoolGetDatum(control->trusted);
        /* relocatable */
        values[4] = BoolGetDatum(control->relocatable);
        /* schema stays the same */
        /* requires */
        if (control->requires == NIL)
          nulls[6] = true;
        else
        {
          values[6] = convert_requires_to_datum(control->requires);
          nulls[6] = false;
        }
        /* comment stays the same */

        tuplestore_putvalues(tupstore, tupdesc, values, nulls);
      }
    }
  }
}

/*
 * Test whether the given extension exists (not whether it's installed)
 *
 * This checks for the existence of a matching control file in the extension
 * directory.  That's not a bulletproof check, since the file might be
 * invalid, but this is only used for hints so it doesn't have to be 100%
 * right.
 */
bool
extension_file_exists(const char *extensionName)
{
  bool    result = false;
  List     *locations;
  DIR      *dir;
  struct dirent *de;

  locations = get_extension_control_directories();

  foreach_ptr(char, location, locations)
  {
    dir = AllocateDir(location);

    /*
     * If the control directory doesn't exist, we want to silently return
     * false.  Any other error will be reported by ReadDir.
     */
    if (dir == NULL && errno == ENOENT)
    {
      /* do nothing */
    }
    else
    {
      while ((de = ReadDir(dir, location)) != NULL)
      {
        char     *extname;

        if (!is_extension_control_filename(de->d_name))
          continue;

        /* extract extension name from 'name.control' filename */
        extname = pstrdup(de->d_name);
        *strrchr(extname, '.') = '\0';

        /* ignore it if it's an auxiliary control file */
        if (strstr(extname, "--"))
          continue;

        /* done if it matches request */
        if (strcmp(extname, extensionName) == 0)
        {
          result = true;
          break;
        }
      }

      FreeDir(dir);
    }
    if (result)
      break;
  }

  return result;
}

/*
 * Convert a list of extension names to a name[] Datum
 */
static Datum
convert_requires_to_datum(List *requires)
{
  Datum    *datums;
  int     ndatums;
  ArrayType  *a;
  ListCell   *lc;

  ndatums = list_length(requires);
  datums = (Datum *) palloc(ndatums * sizeof(Datum));
  ndatums = 0;
  foreach(lc, requires)
  {
    char     *curreq = (char *) lfirst(lc);

    datums[ndatums++] =
      DirectFunctionCall1(namein, CStringGetDatum(curreq));
  }
  a = construct_array_builtin(datums, ndatums, NAMEOID);
  return PointerGetDatum(a);
}

/*
 * This function reports the version update paths that exist for the
 * specified extension.
 */
Datum
pg_extension_update_paths(PG_FUNCTION_ARGS)
{
  Name    extname = PG_GETARG_NAME(0);
  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
  List     *evi_list;
  ExtensionControlFile *control;
  ListCell   *lc1;

  /* Check extension name validity before any filesystem access */
  check_valid_extension_name(NameStr(*extname));

  /* Build tuplestore to hold the result rows */
  InitMaterializedSRF(fcinfo, 0);

  /* Read the extension's control file */
  control = read_extension_control_file(NameStr(*extname));

  /* Extract the version update graph from the script directory */
  evi_list = get_ext_ver_list(control);

  /* Iterate over all pairs of versions */
  foreach(lc1, evi_list)
  {
    ExtensionVersionInfo *evi1 = (ExtensionVersionInfo *) lfirst(lc1);
    ListCell   *lc2;

    foreach(lc2, evi_list)
    {
      ExtensionVersionInfo *evi2 = (ExtensionVersionInfo *) lfirst(lc2);
      List     *path;
      Datum   values[3];
      bool    nulls[3];

      if (evi1 == evi2)
        continue;

      /* Find shortest path from evi1 to evi2 */
      path = find_update_path(evi_list, evi1, evi2, false, true);

      /* Emit result row */
      memset(values, 0, sizeof(values));
      memset(nulls, 0, sizeof(nulls));

      /* source */
      values[0] = CStringGetTextDatum(evi1->name);
      /* target */
      values[1] = CStringGetTextDatum(evi2->name);
      /* path */
      if (path == NIL)
        nulls[2] = true;
      else
      {
        StringInfoData pathbuf;
        ListCell   *lcv;

        initStringInfo(&pathbuf);
        /* The path doesn't include start vertex, but show it */
        appendStringInfoString(&pathbuf, evi1->name);
        foreach(lcv, path)
        {
          char     *versionName = (char *) lfirst(lcv);

          appendStringInfoString(&pathbuf, "--");
          appendStringInfoString(&pathbuf, versionName);
        }
        values[2] = CStringGetTextDatum(pathbuf.data);
        pfree(pathbuf.data);
      }

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

  return (Datum) 0;
}

/*
 * pg_extension_config_dump
 *
 * Record information about a configuration table that belongs to an
 * extension being created, but whose contents should be dumped in whole
 * or in part during pg_dump.
 */
Datum
pg_extension_config_dump(PG_FUNCTION_ARGS)
{
  Oid     tableoid = PG_GETARG_OID(0);
  text     *wherecond = PG_GETARG_TEXT_PP(1);
  char     *tablename;
  Relation  extRel;
  ScanKeyData key[1];
  SysScanDesc extScan;
  HeapTuple extTup;
  Datum   arrayDatum;
  Datum   elementDatum;
  int     arrayLength;
  int     arrayIndex;
  bool    isnull;
  Datum   repl_val[Natts_pg_extension];
  bool    repl_null[Natts_pg_extension];
  bool    repl_repl[Natts_pg_extension];
  ArrayType  *a;

  /*
   * We only allow this to be called from an extension's SQL script. We
   * shouldn't need any permissions check beyond that.
   */
  if (!creating_extension)
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("%s can only be called from an SQL script executed by CREATE EXTENSION",
            "pg_extension_config_dump()")));

  /*
   * Check that the table exists and is a member of the extension being
   * created.  This ensures that we don't need to register an additional
   * dependency to protect the extconfig entry.
   */
  tablename = get_rel_name(tableoid);
  if (tablename == NULL)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_TABLE),
         errmsg("OID %u does not refer to a table", tableoid)));
  if (getExtensionOfObject(RelationRelationId, tableoid) !=
    CurrentExtensionObject)
    ereport(ERROR,
        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
         errmsg("table \"%s\" is not a member of the extension being created",
            tablename)));

  /*
   * Add the table OID and WHERE condition to the extension's extconfig and
   * extcondition arrays.
   *
   * If the table is already in extconfig, treat this as an update of the
   * WHERE condition.
   */

  /* Find the pg_extension tuple */
  extRel = table_open(ExtensionRelationId, RowExclusiveLock);

  ScanKeyInit(&key[0],
        Anum_pg_extension_oid,
        BTEqualStrategyNumber, F_OIDEQ,
        ObjectIdGetDatum(CurrentExtensionObject));

  extScan = systable_beginscan(extRel, ExtensionOidIndexId, true,
                 NULL, 1, key);

  extTup = systable_getnext(extScan);

  if (!HeapTupleIsValid(extTup)) /* should not happen */
    elog(ERROR, "could not find tuple for extension %u",
       CurrentExtensionObject);

  memset(repl_val, 0, sizeof(repl_val));
  memset(repl_null, false, sizeof(repl_null));
  memset(repl_repl, false, sizeof(repl_repl));

  /* Build or modify the extconfig value */
  elementDatum = ObjectIdGetDatum(tableoid);

  arrayDatum = heap_getattr(extTup, Anum_pg_extension_extconfig,
                RelationGetDescr(extRel), &isnull);
  if (isnull)
  {
    /* Previously empty extconfig, so build 1-element array */
    arrayLength = 0;
    arrayIndex = 1;

    a = construct_array_builtin(&elementDatum, 1, OIDOID);
  }
  else
  {
    /* Modify or extend existing extconfig array */
    Oid      *arrayData;
    int     i;

    a = DatumGetArrayTypeP(arrayDatum);

    arrayLength = ARR_DIMS(a)[0];
    if (ARR_NDIM(a) != 1 ||
      ARR_LBOUND(a)[0] != 1 ||
      arrayLength < 0 ||
      ARR_HASNULL(a) ||
      ARR_ELEMTYPE(a) != OIDOID)
      elog(ERROR, "extconfig is not a 1-D Oid array");
    arrayData = (Oid *) ARR_DATA_PTR(a);

    arrayIndex = arrayLength + 1; /* set up to add after end */

    for (i = 0; i < arrayLength; i++)
    {
      if (arrayData[i] == tableoid)
      {
        arrayIndex = i + 1; /* replace this element instead */
        break;
      }
    }

    a = array_set(a, 1, &arrayIndex,
            elementDatum,
            false,
            -1 /* varlena array */ ,
            sizeof(Oid) /* OID's typlen */ ,
            true /* OID's typbyval */ ,
            TYPALIGN_INT /* OID's typalign */ );
  }
  repl_val[Anum_pg_extension_extconfig - 1] = PointerGetDatum(a);
  repl_repl[Anum_pg_extension_extconfig - 1] = true;

  /* Build or modify the extcondition value */
  elementDatum = PointerGetDatum(wherecond);

  arrayDatum = heap_getattr(extTup, Anum_pg_extension_extcondition,
                RelationGetDescr(extRel), &isnull);
  if (isnull)
  {
    if (arrayLength != 0)
      elog(ERROR, "extconfig and extcondition arrays do not match");

    a = construct_array_builtin(&elementDatum, 1, TEXTOID);
  }
  else
  {
    a = DatumGetArrayTypeP(arrayDatum);

    if (ARR_NDIM(a) != 1 ||
      ARR_LBOUND(a)[0] != 1 ||
      ARR_HASNULL(a) ||
      ARR_ELEMTYPE(a) != TEXTOID)
      elog(ERROR, "extcondition is not a 1-D text array");
    if (ARR_DIMS(a)[0] != arrayLength)
      elog(ERROR, "extconfig and extcondition arrays do not match");

    /* Add or replace at same index as in extconfig */
    a = array_set(a, 1, &arrayIndex,
            elementDatum,
            false,
            -1 /* varlena array */ ,
            -1 /* TEXT's typlen */ ,
            false /* TEXT's typbyval */ ,
            TYPALIGN_INT /* TEXT's typalign */ );
  }
  repl_val[Anum_pg_extension_extcondition - 1] = PointerGetDatum(a);
  repl_repl[Anum_pg_extension_extcondition - 1] = true;

  extTup = heap_modify_tuple(extTup, RelationGetDescr(extRel),
                 repl_val, repl_null, repl_repl);

  CatalogTupleUpdate(extRel, &extTup->t_self, extTup);

  systable_endscan(extScan);

  table_close(extRel, RowExclusiveLock);

  PG_RETURN_VOID();
}

/*
 * pg_get_loaded_modules
 *
 * SQL-callable function to get per-loaded-module information.  Modules
 * (shared libraries) aren't necessarily one-to-one with extensions, but
 * they're sufficiently closely related to make this file a good home.
 */
Datum
pg_get_loaded_modules(PG_FUNCTION_ARGS)
{
  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
  DynamicFileList *file_scanner;

  /* Build tuplestore to hold the result rows */
  InitMaterializedSRF(fcinfo, 0);

  for (file_scanner = get_first_loaded_module(); file_scanner != NULL;
     file_scanner = get_next_loaded_module(file_scanner))
  {
    const char *library_path,
           *module_name,
           *module_version;
    const char *sep;
    Datum   values[3] = {0};
    bool    nulls[3] = {0};

    get_loaded_module_details(file_scanner,
                  &library_path,
                  &module_name,
                  &module_version);

    if (module_name == NULL)
      nulls[0] = true;
    else
      values[0] = CStringGetTextDatum(module_name);
    if (module_version == NULL)
      nulls[1] = true;
    else
      values[1] = CStringGetTextDatum(module_version);

    /* For security reasons, we don't show the directory path */
    sep = last_dir_separator(library_path);
    if (sep)
      library_path = sep + 1;
    values[2] = CStringGetTextDatum(library_path);

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

  return (Datum) 0;
}

/*
 * extension_config_remove
 *
 * Remove the specified table OID from extension's extconfig, if present.
 * This is not currently exposed as a function, but it could be;
 * for now, we just invoke it from ALTER EXTENSION DROP.
 */
static void
extension_config_remove(Oid extensionoid, Oid tableoid)
{
  Relation  extRel;
  ScanKeyData key[1];
  SysScanDesc extScan;
  HeapTuple extTup;
  Datum   arrayDatum;
  int     arrayLength;
  int     arrayIndex;
  bool    isnull;
  Datum   repl_val[Natts_pg_extension];
  bool    repl_null[Natts_pg_extension];
  bool    repl_repl[Natts_pg_extension];
  ArrayType  *a;

  /* Find the pg_extension tuple */
  extRel = table_open(ExtensionRelationId, RowExclusiveLock);

  ScanKeyInit(&key[0],
        Anum_pg_extension_oid,
        BTEqualStrategyNumber, F_OIDEQ,
        ObjectIdGetDatum(extensionoid));

  extScan = systable_beginscan(extRel, ExtensionOidIndexId, true,
                 NULL, 1, key);

  extTup = systable_getnext(extScan);

  if (!HeapTupleIsValid(extTup)) /* should not happen */
    elog(ERROR, "could not find tuple for extension %u",
       extensionoid);

  /* Search extconfig for the tableoid */
  arrayDatum = heap_getattr(extTup, Anum_pg_extension_extconfig,
                RelationGetDescr(extRel), &isnull);
  if (isnull)
  {
    /* nothing to do */
    a = NULL;
    arrayLength = 0;
    arrayIndex = -1;
  }
  else
  {
    Oid      *arrayData;
    int     i;

    a = DatumGetArrayTypeP(arrayDatum);

    arrayLength = ARR_DIMS(a)[0];
    if (ARR_NDIM(a) != 1 ||
      ARR_LBOUND(a)[0] != 1 ||
      arrayLength < 0 ||
      ARR_HASNULL(a) ||
      ARR_ELEMTYPE(a) != OIDOID)
      elog(ERROR, "extconfig is not a 1-D Oid array");
    arrayData = (Oid *) ARR_DATA_PTR(a);

    arrayIndex = -1;    /* flag for no deletion needed */

    for (i = 0; i < arrayLength; i++)
    {
      if (arrayData[i] == tableoid)
      {
        arrayIndex = i; /* index to remove */
        break;
      }
    }
  }

  /* If tableoid is not in extconfig, nothing to do */
  if (arrayIndex < 0)
  {
    systable_endscan(extScan);
    table_close(extRel, RowExclusiveLock);
    return;
  }

  /* Modify or delete the extconfig value */
  memset(repl_val, 0, sizeof(repl_val));
  memset(repl_null, false, sizeof(repl_null));
  memset(repl_repl, false, sizeof(repl_repl));

  if (arrayLength <= 1)
  {
    /* removing only element, just set array to null */
    repl_null[Anum_pg_extension_extconfig - 1] = true;
  }
  else
  {
    /* squeeze out the target element */
    Datum    *dvalues;
    int     nelems;
    int     i;

    /* We already checked there are no nulls */
    deconstruct_array_builtin(a, OIDOID, &dvalues, NULL, &nelems);

    for (i = arrayIndex; i < arrayLength - 1; i++)
      dvalues[i] = dvalues[i + 1];

    a = construct_array_builtin(dvalues, arrayLength - 1, OIDOID);

    repl_val[Anum_pg_extension_extconfig - 1] = PointerGetDatum(a);
  }
  repl_repl[Anum_pg_extension_extconfig - 1] = true;

  /* Modify or delete the extcondition value */
  arrayDatum = heap_getattr(extTup, Anum_pg_extension_extcondition,
                RelationGetDescr(extRel), &isnull);
  if (isnull)
  {
    elog(ERROR, "extconfig and extcondition arrays do not match");
  }
  else
  {
    a = DatumGetArrayTypeP(arrayDatum);

    if (ARR_NDIM(a) != 1 ||
      ARR_LBOUND(a)[0] != 1 ||
      ARR_HASNULL(a) ||
      ARR_ELEMTYPE(a) != TEXTOID)
      elog(ERROR, "extcondition is not a 1-D text array");
    if (ARR_DIMS(a)[0] != arrayLength)
      elog(ERROR, "extconfig and extcondition arrays do not match");
  }

  if (arrayLength <= 1)
  {
    /* removing only element, just set array to null */
    repl_null[Anum_pg_extension_extcondition - 1] = true;
  }
  else
  {
    /* squeeze out the target element */
    Datum    *dvalues;
    int     nelems;
    int     i;

    /* We already checked there are no nulls */
    deconstruct_array_builtin(a, TEXTOID, &dvalues, NULL, &nelems);

    for (i = arrayIndex; i < arrayLength - 1; i++)
      dvalues[i] = dvalues[i + 1];

    a = construct_array_builtin(dvalues, arrayLength - 1, TEXTOID);

    repl_val[Anum_pg_extension_extcondition - 1] = PointerGetDatum(a);
  }
  repl_repl[Anum_pg_extension_extcondition - 1] = true;

  extTup = heap_modify_tuple(extTup, RelationGetDescr(extRel),
                 repl_val, repl_null, repl_repl);

  CatalogTupleUpdate(extRel, &extTup->t_self, extTup);

  systable_endscan(extScan);

  table_close(extRel, RowExclusiveLock);
}

/*
 * Execute ALTER EXTENSION SET SCHEMA
 */
ObjectAddress
AlterExtensionNamespace(const char *extensionName, const char *newschema, Oid *oldschema)
{
  Oid     extensionOid;
  Oid     nspOid;
  Oid     oldNspOid;
  AclResult aclresult;
  Relation  extRel;
  ScanKeyData key[2];
  SysScanDesc extScan;
  HeapTuple extTup;
  Form_pg_extension extForm;
  Relation  depRel;
  SysScanDesc depScan;
  HeapTuple depTup;
  ObjectAddresses *objsMoved;
  ObjectAddress extAddr;

  extensionOid = get_extension_oid(extensionName, false);

  nspOid = LookupCreationNamespace(newschema);

  /*
   * Permission check: must own extension.  Note that we don't bother to
   * check ownership of the individual member objects ...
   */
  if (!object_ownercheck(ExtensionRelationId, extensionOid, GetUserId()))
    aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_EXTENSION,
             extensionName);

  /* Permission check: must have creation rights in target namespace */
  aclresult = object_aclcheck(NamespaceRelationId, nspOid, GetUserId(), ACL_CREATE);
  if (aclresult != ACLCHECK_OK)
    aclcheck_error(aclresult, OBJECT_SCHEMA, newschema);

  /*
   * If the schema is currently a member of the extension, disallow moving
   * the extension into the schema.  That would create a dependency loop.
   */
  if (getExtensionOfObject(NamespaceRelationId, nspOid) == extensionOid)
    ereport(ERROR,
        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
         errmsg("cannot move extension \"%s\" into schema \"%s\" "
            "because the extension contains the schema",
            extensionName, newschema)));

  /* Locate the pg_extension tuple */
  extRel = table_open(ExtensionRelationId, RowExclusiveLock);

  ScanKeyInit(&key[0],
        Anum_pg_extension_oid,
        BTEqualStrategyNumber, F_OIDEQ,
        ObjectIdGetDatum(extensionOid));

  extScan = systable_beginscan(extRel, ExtensionOidIndexId, true,
                 NULL, 1, key);

  extTup = systable_getnext(extScan);

  if (!HeapTupleIsValid(extTup)) /* should not happen */
    elog(ERROR, "could not find tuple for extension %u",
       extensionOid);

  /* Copy tuple so we can modify it below */
  extTup = heap_copytuple(extTup);
  extForm = (Form_pg_extension) GETSTRUCT(extTup);

  systable_endscan(extScan);

  /*
   * If the extension is already in the target schema, just silently do
   * nothing.
   */
  if (extForm->extnamespace == nspOid)
  {
    table_close(extRel, RowExclusiveLock);
    return InvalidObjectAddress;
  }

  /* Check extension is supposed to be relocatable */
  if (!extForm->extrelocatable)
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("extension \"%s\" does not support SET SCHEMA",
            NameStr(extForm->extname))));

  objsMoved = new_object_addresses();

  /* store the OID of the namespace to-be-changed */
  oldNspOid = extForm->extnamespace;

  /*
   * Scan pg_depend to find objects that depend directly on the extension,
   * and alter each one's schema.
   */
  depRel = table_open(DependRelationId, AccessShareLock);

  ScanKeyInit(&key[0],
        Anum_pg_depend_refclassid,
        BTEqualStrategyNumber, F_OIDEQ,
        ObjectIdGetDatum(ExtensionRelationId));
  ScanKeyInit(&key[1],
        Anum_pg_depend_refobjid,
        BTEqualStrategyNumber, F_OIDEQ,
        ObjectIdGetDatum(extensionOid));

  depScan = systable_beginscan(depRel, DependReferenceIndexId, true,
                 NULL, 2, key);

  while (HeapTupleIsValid(depTup = systable_getnext(depScan)))
  {
    Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
    ObjectAddress dep;
    Oid     dep_oldNspOid;

    /*
     * If a dependent extension has a no_relocate request for this
     * extension, disallow SET SCHEMA.  (XXX it's a bit ugly to do this in
     * the same loop that's actually executing the renames: we may detect
     * the error condition only after having expended a fair amount of
     * work.  However, the alternative is to do two scans of pg_depend,
     * which seems like optimizing for failure cases.  The rename work
     * will all roll back cleanly enough if we do fail here.)
     */
    if (pg_depend->deptype == DEPENDENCY_NORMAL &&
      pg_depend->classid == ExtensionRelationId)
    {
      char     *depextname = get_extension_name(pg_depend->objid);
      ExtensionControlFile *dcontrol;
      ListCell   *lc;

      dcontrol = read_extension_control_file(depextname);
      foreach(lc, dcontrol->no_relocate)
      {
        char     *nrextname = (char *) lfirst(lc);

        if (strcmp(nrextname, NameStr(extForm->extname)) == 0)
        {
          ereport(ERROR,
              (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
               errmsg("cannot SET SCHEMA of extension \"%s\" because other extensions prevent it",
                  NameStr(extForm->extname)),
               errdetail("Extension \"%s\" requests no relocation of extension \"%s\".",
                     depextname,
                     NameStr(extForm->extname))));
        }
      }
    }

    /*
     * Otherwise, ignore non-membership dependencies.  (Currently, the
     * only other case we could see here is a normal dependency from
     * another extension.)
     */
    if (pg_depend->deptype != DEPENDENCY_EXTENSION)
      continue;

    dep.classId = pg_depend->classid;
    dep.objectId = pg_depend->objid;
    dep.objectSubId = pg_depend->objsubid;

    if (dep.objectSubId != 0) /* should not happen */
      elog(ERROR, "extension should not have a sub-object dependency");

    /* Relocate the object */
    dep_oldNspOid = AlterObjectNamespace_oid(dep.classId,
                         dep.objectId,
                         nspOid,
                         objsMoved);

    /*
     * If not all the objects had the same old namespace (ignoring any
     * that are not in namespaces or are dependent types), complain.
     */
    if (dep_oldNspOid != InvalidOid && dep_oldNspOid != oldNspOid)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("extension \"%s\" does not support SET SCHEMA",
              NameStr(extForm->extname)),
           errdetail("%s is not in the extension's schema \"%s\"",
                 getObjectDescription(&dep, false),
                 get_namespace_name(oldNspOid))));
  }

  /* report old schema, if caller wants it */
  if (oldschema)
    *oldschema = oldNspOid;

  systable_endscan(depScan);

  relation_close(depRel, AccessShareLock);

  /* Now adjust pg_extension.extnamespace */
  extForm->extnamespace = nspOid;

  CatalogTupleUpdate(extRel, &extTup->t_self, extTup);

  table_close(extRel, RowExclusiveLock);

  /* update dependency to point to the new schema */
  if (changeDependencyFor(ExtensionRelationId, extensionOid,
              NamespaceRelationId, oldNspOid, nspOid) != 1)
    elog(ERROR, "could not change schema dependency for extension %s",
       NameStr(extForm->extname));

  InvokeObjectPostAlterHook(ExtensionRelationId, extensionOid, 0);

  ObjectAddressSet(extAddr, ExtensionRelationId, extensionOid);

  return extAddr;
}

/*
 * Execute ALTER EXTENSION UPDATE
 */
ObjectAddress
ExecAlterExtensionStmt(ParseState *pstate, AlterExtensionStmt *stmt)
{
  DefElem    *d_new_version = NULL;
  char     *versionName;
  char     *oldVersionName;
  ExtensionControlFile *control;
  Oid     extensionOid;
  Relation  extRel;
  ScanKeyData key[1];
  SysScanDesc extScan;
  HeapTuple extTup;
  List     *updateVersions;
  Datum   datum;
  bool    isnull;
  ListCell   *lc;
  ObjectAddress address;

  /*
   * We use global variables to track the extension being created, so we can
   * create/update only one extension at the same time.
   */
  if (creating_extension)
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("nested ALTER EXTENSION is not supported")));

  /*
   * Look up the extension --- it must already exist in pg_extension
   */
  extRel = table_open(ExtensionRelationId, AccessShareLock);

  ScanKeyInit(&key[0],
        Anum_pg_extension_extname,
        BTEqualStrategyNumber, F_NAMEEQ,
        CStringGetDatum(stmt->extname));

  extScan = systable_beginscan(extRel, ExtensionNameIndexId, true,
                 NULL, 1, key);

  extTup = systable_getnext(extScan);

  if (!HeapTupleIsValid(extTup))
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("extension \"%s\" does not exist",
            stmt->extname)));

  extensionOid = ((Form_pg_extension) GETSTRUCT(extTup))->oid;

  /*
   * Determine the existing version we are updating from
   */
  datum = heap_getattr(extTup, Anum_pg_extension_extversion,
             RelationGetDescr(extRel), &isnull);
  if (isnull)
    elog(ERROR, "extversion is null");
  oldVersionName = text_to_cstring(DatumGetTextPP(datum));

  systable_endscan(extScan);

  table_close(extRel, AccessShareLock);

  /* Permission check: must own extension */
  if (!object_ownercheck(ExtensionRelationId, extensionOid, GetUserId()))
    aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_EXTENSION,
             stmt->extname);

  /*
   * Read the primary control file.  Note we assume that it does not contain
   * any non-ASCII data, so there is no need to worry about encoding at this
   * point.
   */
  control = read_extension_control_file(stmt->extname);

  /*
   * Read the statement option list
   */
  foreach(lc, stmt->options)
  {
    DefElem    *defel = (DefElem *) lfirst(lc);

    if (strcmp(defel->defname, "new_version") == 0)
    {
      if (d_new_version)
        errorConflictingDefElem(defel, pstate);
      d_new_version = defel;
    }
    else
      elog(ERROR, "unrecognized option: %s", defel->defname);
  }

  /*
   * Determine the version to update to
   */
  if (d_new_version && d_new_version->arg)
    versionName = strVal(d_new_version->arg);
  else if (control->default_version)
    versionName = control->default_version;
  else
  {
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("version to install must be specified")));
    versionName = NULL;   /* keep compiler quiet */
  }
  check_valid_version_name(versionName);

  /*
   * If we're already at that version, just say so
   */
  if (strcmp(oldVersionName, versionName) == 0)
  {
    ereport(NOTICE,
        (errmsg("version \"%s\" of extension \"%s\" is already installed",
            versionName, stmt->extname)));
    return InvalidObjectAddress;
  }

  /*
   * Identify the series of update script files we need to execute
   */
  updateVersions = identify_update_path(control,
                      oldVersionName,
                      versionName);

  /*
   * Update the pg_extension row and execute the update scripts, one at a
   * time
   */
  ApplyExtensionUpdates(extensionOid, control,
              oldVersionName, updateVersions,
              NULL, false, false);

  ObjectAddressSet(address, ExtensionRelationId, extensionOid);

  return address;
}

/*
 * Apply a series of update scripts as though individual ALTER EXTENSION
 * UPDATE commands had been given, including altering the pg_extension row
 * and dependencies each time.
 *
 * This might be more work than necessary, but it ensures that old update
 * scripts don't break if newer versions have different control parameters.
 */
static void
ApplyExtensionUpdates(Oid extensionOid,
            ExtensionControlFile *pcontrol,
            const char *initialVersion,
            List *updateVersions,
            char *origSchemaName,
            bool cascade,
            bool is_create)
{
  const char *oldVersionName = initialVersion;
  ListCell   *lcv;

  foreach(lcv, updateVersions)
  {
    char     *versionName = (char *) lfirst(lcv);
    ExtensionControlFile *control;
    char     *schemaName;
    Oid     schemaOid;
    List     *requiredExtensions;
    List     *requiredSchemas;
    Relation  extRel;
    ScanKeyData key[1];
    SysScanDesc extScan;
    HeapTuple extTup;
    Form_pg_extension extForm;
    Datum   values[Natts_pg_extension];
    bool    nulls[Natts_pg_extension];
    bool    repl[Natts_pg_extension];
    ObjectAddress myself;
    ListCell   *lc;

    /*
     * Fetch parameters for specific version (pcontrol is not changed)
     */
    control = read_extension_aux_control_file(pcontrol, versionName);

    /* Find the pg_extension tuple */
    extRel = table_open(ExtensionRelationId, RowExclusiveLock);

    ScanKeyInit(&key[0],
          Anum_pg_extension_oid,
          BTEqualStrategyNumber, F_OIDEQ,
          ObjectIdGetDatum(extensionOid));

    extScan = systable_beginscan(extRel, ExtensionOidIndexId, true,
                   NULL, 1, key);

    extTup = systable_getnext(extScan);

    if (!HeapTupleIsValid(extTup)) /* should not happen */
      elog(ERROR, "could not find tuple for extension %u",
         extensionOid);

    extForm = (Form_pg_extension) GETSTRUCT(extTup);

    /*
     * Determine the target schema (set by original install)
     */
    schemaOid = extForm->extnamespace;
    schemaName = get_namespace_name(schemaOid);

    /*
     * Modify extrelocatable and extversion in the pg_extension tuple
     */
    memset(values, 0, sizeof(values));
    memset(nulls, 0, sizeof(nulls));
    memset(repl, 0, sizeof(repl));

    values[Anum_pg_extension_extrelocatable - 1] =
      BoolGetDatum(control->relocatable);
    repl[Anum_pg_extension_extrelocatable - 1] = true;
    values[Anum_pg_extension_extversion - 1] =
      CStringGetTextDatum(versionName);
    repl[Anum_pg_extension_extversion - 1] = true;

    extTup = heap_modify_tuple(extTup, RelationGetDescr(extRel),
                   values, nulls, repl);

    CatalogTupleUpdate(extRel, &extTup->t_self, extTup);

    systable_endscan(extScan);

    table_close(extRel, RowExclusiveLock);

    /*
     * Look up the prerequisite extensions for this version, install them
     * if necessary, and build lists of their OIDs and the OIDs of their
     * target schemas.
     */
    requiredExtensions = NIL;
    requiredSchemas = NIL;
    foreach(lc, control->requires)
    {
      char     *curreq = (char *) lfirst(lc);
      Oid     reqext;
      Oid     reqschema;

      reqext = get_required_extension(curreq,
                      control->name,
                      origSchemaName,
                      cascade,
                      NIL,
                      is_create);
      reqschema = get_extension_schema(reqext);
      requiredExtensions = lappend_oid(requiredExtensions, reqext);
      requiredSchemas = lappend_oid(requiredSchemas, reqschema);
    }

    /*
     * Remove and recreate dependencies on prerequisite extensions
     */
    deleteDependencyRecordsForClass(ExtensionRelationId, extensionOid,
                    ExtensionRelationId,
                    DEPENDENCY_NORMAL);

    myself.classId = ExtensionRelationId;
    myself.objectId = extensionOid;
    myself.objectSubId = 0;

    foreach(lc, requiredExtensions)
    {
      Oid     reqext = lfirst_oid(lc);
      ObjectAddress otherext;

      otherext.classId = ExtensionRelationId;
      otherext.objectId = reqext;
      otherext.objectSubId = 0;

      recordDependencyOn(&myself, &otherext, DEPENDENCY_NORMAL);
    }

    InvokeObjectPostAlterHook(ExtensionRelationId, extensionOid, 0);

    /*
     * Finally, execute the update script file
     */
    execute_extension_script(extensionOid, control,
                 oldVersionName, versionName,
                 requiredSchemas,
                 schemaName);

    /*
     * Update prior-version name and loop around.  Since
     * execute_sql_string did a final CommandCounterIncrement, we can
     * update the pg_extension row again.
     */
    oldVersionName = versionName;
  }
}

/*
 * Execute ALTER EXTENSION ADD/DROP
 *
 * Return value is the address of the altered extension.
 *
 * objAddr is an output argument which, if not NULL, is set to the address of
 * the added/dropped object.
 */
ObjectAddress
ExecAlterExtensionContentsStmt(AlterExtensionContentsStmt *stmt,
                 ObjectAddress *objAddr)
{
  ObjectAddress extension;
  ObjectAddress object;
  Relation  relation;

  switch (stmt->objtype)
  {
    case OBJECT_DATABASE:
    case OBJECT_EXTENSION:
    case OBJECT_INDEX:
    case OBJECT_PUBLICATION:
    case OBJECT_ROLE:
    case OBJECT_STATISTIC_EXT:
    case OBJECT_SUBSCRIPTION:
    case OBJECT_TABLESPACE:
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
           errmsg("cannot add an object of this type to an extension")));
      break;
    default:
      /* OK */
      break;
  }

  /*
   * Find the extension and acquire a lock on it, to ensure it doesn't get
   * dropped concurrently.  A sharable lock seems sufficient: there's no
   * reason not to allow other sorts of manipulations, such as add/drop of
   * other objects, to occur concurrently.  Concurrently adding/dropping the
   * *same* object would be bad, but we prevent that by using a non-sharable
   * lock on the individual object, below.
   */
  extension = get_object_address(OBJECT_EXTENSION,
                   (Node *) makeString(stmt->extname),
                   &relation, AccessShareLock, false);

  /* Permission check: must own extension */
  if (!object_ownercheck(ExtensionRelationId, extension.objectId, GetUserId()))
    aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_EXTENSION,
             stmt->extname);

  /*
   * Translate the parser representation that identifies the object into an
   * ObjectAddress.  get_object_address() will throw an error if the object
   * does not exist, and will also acquire a lock on the object to guard
   * against concurrent DROP and ALTER EXTENSION ADD/DROP operations.
   */
  object = get_object_address(stmt->objtype, stmt->object,
                &relation, ShareUpdateExclusiveLock, false);

  Assert(object.objectSubId == 0);
  if (objAddr)
    *objAddr = object;

  /* Permission check: must own target object, too */
  check_object_ownership(GetUserId(), stmt->objtype, object,
               stmt->object, relation);

  /* Do the update, recursing to any dependent objects */
  ExecAlterExtensionContentsRecurse(stmt, extension, object);

  /* Finish up */
  InvokeObjectPostAlterHook(ExtensionRelationId, extension.objectId, 0);

  /*
   * If get_object_address() opened the relation for us, we close it to keep
   * the reference count correct - but we retain any locks acquired by
   * get_object_address() until commit time, to guard against concurrent
   * activity.
   */
  if (relation != NULL)
    relation_close(relation, NoLock);

  return extension;
}

/*
 * ExecAlterExtensionContentsRecurse
 *    Subroutine for ExecAlterExtensionContentsStmt
 *
 * Do the bare alteration of object's membership in extension,
 * without permission checks.  Recurse to dependent objects, if any.
 */
static void
ExecAlterExtensionContentsRecurse(AlterExtensionContentsStmt *stmt,
                  ObjectAddress extension,
                  ObjectAddress object)
{
  Oid     oldExtension;

  /*
   * Check existing extension membership.
   */
  oldExtension = getExtensionOfObject(object.classId, object.objectId);

  if (stmt->action > 0)
  {
    /*
     * ADD, so complain if object is already attached to some extension.
     */
    if (OidIsValid(oldExtension))
      ereport(ERROR,
          (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
           errmsg("%s is already a member of extension \"%s\"",
              getObjectDescription(&object, false),
              get_extension_name(oldExtension))));

    /*
     * Prevent a schema from being added to an extension if the schema
     * contains the extension.  That would create a dependency loop.
     */
    if (object.classId == NamespaceRelationId &&
      object.objectId == get_extension_schema(extension.objectId))
      ereport(ERROR,
          (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
           errmsg("cannot add schema \"%s\" to extension \"%s\" "
              "because the schema contains the extension",
              get_namespace_name(object.objectId),
              stmt->extname)));

    /*
     * OK, add the dependency.
     */
    recordDependencyOn(&object, &extension, DEPENDENCY_EXTENSION);

    /*
     * Also record the initial ACL on the object, if any.
     *
     * Note that this will handle the object's ACLs, as well as any ACLs
     * on object subIds.  (In other words, when the object is a table,
     * this will record the table's ACL and the ACLs for the columns on
     * the table, if any).
     */
    recordExtObjInitPriv(object.objectId, object.classId);
  }
  else
  {
    /*
     * DROP, so complain if it's not a member.
     */
    if (oldExtension != extension.objectId)
      ereport(ERROR,
          (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
           errmsg("%s is not a member of extension \"%s\"",
              getObjectDescription(&object, false),
              stmt->extname)));

    /*
     * OK, drop the dependency.
     */
    if (deleteDependencyRecordsForClass(object.classId, object.objectId,
                      ExtensionRelationId,
                      DEPENDENCY_EXTENSION) != 1)
      elog(ERROR, "unexpected number of extension dependency records");

    /*
     * If it's a relation, it might have an entry in the extension's
     * extconfig array, which we must remove.
     */
    if (object.classId == RelationRelationId)
      extension_config_remove(extension.objectId, object.objectId);

    /*
     * Remove all the initial ACLs, if any.
     *
     * Note that this will remove the object's ACLs, as well as any ACLs
     * on object subIds.  (In other words, when the object is a table,
     * this will remove the table's ACL and the ACLs for the columns on
     * the table, if any).
     */
    removeExtObjInitPriv(object.objectId, object.classId);
  }

  /*
   * Recurse to any dependent objects; currently, this includes the array
   * type of a base type, the multirange type associated with a range type,
   * and the rowtype of a table.
   */
  if (object.classId == TypeRelationId)
  {
    ObjectAddress depobject;

    depobject.classId = TypeRelationId;
    depobject.objectSubId = 0;

    /* If it has an array type, update that too */
    depobject.objectId = get_array_type(object.objectId);
    if (OidIsValid(depobject.objectId))
      ExecAlterExtensionContentsRecurse(stmt, extension, depobject);

    /* If it is a range type, update the associated multirange too */
    if (type_is_range(object.objectId))
    {
      depobject.objectId = get_range_multirange(object.objectId);
      if (!OidIsValid(depobject.objectId))
        ereport(ERROR,
            (errcode(ERRCODE_UNDEFINED_OBJECT),
             errmsg("could not find multirange type for data type %s",
                format_type_be(object.objectId))));
      ExecAlterExtensionContentsRecurse(stmt, extension, depobject);
    }
  }
  if (object.classId == RelationRelationId)
  {
    ObjectAddress depobject;

    depobject.classId = TypeRelationId;
    depobject.objectSubId = 0;

    /* It might not have a rowtype, but if it does, update that */
    depobject.objectId = get_rel_type_id(object.objectId);
    if (OidIsValid(depobject.objectId))
      ExecAlterExtensionContentsRecurse(stmt, extension, depobject);
  }
}

/*
 * Read the whole of file into memory.
 *
 * The file contents are returned as a single palloc'd chunk. For convenience
 * of the callers, an extra \0 byte is added to the end.  That is not counted
 * in the length returned into *length.
 */
static char *
read_whole_file(const char *filename, int *length)
{
  char     *buf;
  FILE     *file;
  size_t    bytes_to_read;
  struct stat fst;

  if (stat(filename, &fst) < 0)
    ereport(ERROR,
        (errcode_for_file_access(),
         errmsg("could not stat file \"%s\": %m", filename)));

  if (fst.st_size > (MaxAllocSize - 1))
    ereport(ERROR,
        (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
         errmsg("file \"%s\" is too large", filename)));
  bytes_to_read = (size_t) fst.st_size;

  if ((file = AllocateFile(filename, PG_BINARY_R)) == NULL)
    ereport(ERROR,
        (errcode_for_file_access(),
         errmsg("could not open file \"%s\" for reading: %m",
            filename)));

  buf = (char *) palloc(bytes_to_read + 1);

  bytes_to_read = fread(buf, 1, bytes_to_read, file);

  if (ferror(file))
    ereport(ERROR,
        (errcode_for_file_access(),
         errmsg("could not read file \"%s\": %m", filename)));

  FreeFile(file);

  buf[bytes_to_read] = '\0';

  /*
   * On Windows, manually convert Windows-style newlines (\r\n) to the Unix
   * convention of \n only.  This avoids gotchas due to script files
   * possibly getting converted when being transferred between platforms.
   * Ideally we'd do this by using text mode to read the file, but that also
   * causes control-Z to be treated as end-of-file.  Historically we've
   * allowed control-Z in script files, so breaking that seems unwise.
   */
#ifdef WIN32
  {
    char     *s,
           *d;

    for (s = d = buf; *s; s++)
    {
      if (!(*s == '\r' && s[1] == '\n'))
        *d++ = *s;
    }
    *d = '\0';
    bytes_to_read = d - buf;
  }
#endif

  *length = bytes_to_read;
  return buf;
}

static ExtensionControlFile *
new_ExtensionControlFile(const char *extname)
{
  /*
   * Set up default values.  Pointer fields are initially null.
   */
  ExtensionControlFile *control = palloc0_object(ExtensionControlFile);

  control->name = pstrdup(extname);
  control->relocatable = false;
  control->superuser = true;
  control->trusted = false;
  control->encoding = -1;

  return control;
}

/*
 * Work in a very similar way with find_in_path but it receives an already
 * parsed List of paths to search the basename and it do not support macro
 * replacement or custom error messages (for simplicity).
 *
 * By "already parsed List of paths" this function expected that paths already
 * have all macros replaced.
 */
char *
find_in_paths(const char *basename, List *paths)
{
  ListCell   *cell;

  foreach(cell, paths)
  {
    char     *path = lfirst(cell);
    char     *full;

    Assert(path != NULL);

    path = pstrdup(path);
    canonicalize_path(path);

    /* only absolute paths */
    if (!is_absolute_path(path))
      ereport(ERROR,
          errcode(ERRCODE_INVALID_NAME),
          errmsg("component in parameter \"%s\" is not an absolute path", "extension_control_path"));

    full = psprintf("%s/%s", path, basename);

    if (pg_file_exists(full))
      return full;

    pfree(path);
    pfree(full);
  }

  return NULL;
}

Coverage Report

Created: 2025-06-15 06:31