/src/postgres/src/backend/catalog/namespace.c

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/*-------------------------------------------------------------------------
 *
 * namespace.c
 *    code to support accessing and searching namespaces
 *
 * This is separate from pg_namespace.c, which contains the routines that
 * directly manipulate the pg_namespace system catalog.  This module
 * provides routines associated with defining a "namespace search path"
 * and implementing search-path-controlled searches.
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/catalog/namespace.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "access/parallel.h"
#include "access/xact.h"
#include "access/xlog.h"
#include "catalog/dependency.h"
#include "catalog/namespace.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_conversion.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_opfamily.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_ts_config.h"
#include "catalog/pg_ts_dict.h"
#include "catalog/pg_ts_parser.h"
#include "catalog/pg_ts_template.h"
#include "catalog/pg_type.h"
#include "commands/dbcommands.h"
#include "common/hashfn_unstable.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "storage/ipc.h"
#include "storage/lmgr.h"
#include "storage/procarray.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/guc_hooks.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/varlena.h"


/*
 * The namespace search path is a possibly-empty list of namespace OIDs.
 * In addition to the explicit list, implicitly-searched namespaces
 * may be included:
 *
 * 1. If a TEMP table namespace has been initialized in this session, it
 * is implicitly searched first.
 *
 * 2. The system catalog namespace is always searched.  If the system
 * namespace is present in the explicit path then it will be searched in
 * the specified order; otherwise it will be searched after TEMP tables and
 * *before* the explicit list.  (It might seem that the system namespace
 * should be implicitly last, but this behavior appears to be required by
 * SQL99.  Also, this provides a way to search the system namespace first
 * without thereby making it the default creation target namespace.)
 *
 * For security reasons, searches using the search path will ignore the temp
 * namespace when searching for any object type other than relations and
 * types.  (We must allow types since temp tables have rowtypes.)
 *
 * The default creation target namespace is always the first element of the
 * explicit list.  If the explicit list is empty, there is no default target.
 *
 * The textual specification of search_path can include "$user" to refer to
 * the namespace named the same as the current user, if any.  (This is just
 * ignored if there is no such namespace.)  Also, it can include "pg_temp"
 * to refer to the current backend's temp namespace.  This is usually also
 * ignorable if the temp namespace hasn't been set up, but there's a special
 * case: if "pg_temp" appears first then it should be the default creation
 * target.  We kluge this case a little bit so that the temp namespace isn't
 * set up until the first attempt to create something in it.  (The reason for
 * klugery is that we can't create the temp namespace outside a transaction,
 * but initial GUC processing of search_path happens outside a transaction.)
 * activeTempCreationPending is true if "pg_temp" appears first in the string
 * but is not reflected in activeCreationNamespace because the namespace isn't
 * set up yet.
 *
 * In bootstrap mode, the search path is set equal to "pg_catalog", so that
 * the system namespace is the only one searched or inserted into.
 * initdb is also careful to set search_path to "pg_catalog" for its
 * post-bootstrap standalone backend runs.  Otherwise the default search
 * path is determined by GUC.  The factory default path contains the PUBLIC
 * namespace (if it exists), preceded by the user's personal namespace
 * (if one exists).
 *
 * activeSearchPath is always the actually active path; it points to
 * baseSearchPath which is the list derived from namespace_search_path.
 *
 * If baseSearchPathValid is false, then baseSearchPath (and other derived
 * variables) need to be recomputed from namespace_search_path, or retrieved
 * from the search path cache if there haven't been any syscache
 * invalidations.  We mark it invalid upon an assignment to
 * namespace_search_path or receipt of a syscache invalidation event for
 * pg_namespace or pg_authid.  The recomputation is done during the next
 * lookup attempt.
 *
 * Any namespaces mentioned in namespace_search_path that are not readable
 * by the current user ID are simply left out of baseSearchPath; so
 * we have to be willing to recompute the path when current userid changes.
 * namespaceUser is the userid the path has been computed for.
 *
 * Note: all data pointed to by these List variables is in TopMemoryContext.
 *
 * activePathGeneration is incremented whenever the effective values of
 * activeSearchPath/activeCreationNamespace/activeTempCreationPending change.
 * This can be used to quickly detect whether any change has happened since
 * a previous examination of the search path state.
 */

/* These variables define the actually active state: */

static List *activeSearchPath = NIL;

/* default place to create stuff; if InvalidOid, no default */
static Oid  activeCreationNamespace = InvalidOid;

/* if true, activeCreationNamespace is wrong, it should be temp namespace */
static bool activeTempCreationPending = false;

/* current generation counter; make sure this is never zero */
static uint64 activePathGeneration = 1;

/* These variables are the values last derived from namespace_search_path: */

static List *baseSearchPath = NIL;

static Oid  baseCreationNamespace = InvalidOid;

static bool baseTempCreationPending = false;

static Oid  namespaceUser = InvalidOid;

/* The above four values are valid only if baseSearchPathValid */
static bool baseSearchPathValid = true;

/*
 * Storage for search path cache.  Clear searchPathCacheValid as a simple
 * way to invalidate *all* the cache entries, not just the active one.
 */
static bool searchPathCacheValid = false;
static MemoryContext SearchPathCacheContext = NULL;

typedef struct SearchPathCacheKey
{
  const char *searchPath;
  Oid     roleid;
} SearchPathCacheKey;

typedef struct SearchPathCacheEntry
{
  SearchPathCacheKey key;
  List     *oidlist;    /* namespace OIDs that pass ACL checks */
  List     *finalPath;    /* cached final computed search path */
  Oid     firstNS;    /* first explicitly-listed namespace */
  bool    temp_missing;
  bool    forceRecompute; /* force recompute of finalPath */

  /* needed for simplehash */
  char    status;
} SearchPathCacheEntry;

/*
 * myTempNamespace is InvalidOid until and unless a TEMP namespace is set up
 * in a particular backend session (this happens when a CREATE TEMP TABLE
 * command is first executed).  Thereafter it's the OID of the temp namespace.
 *
 * myTempToastNamespace is the OID of the namespace for my temp tables' toast
 * tables.  It is set when myTempNamespace is, and is InvalidOid before that.
 *
 * myTempNamespaceSubID shows whether we've created the TEMP namespace in the
 * current subtransaction.  The flag propagates up the subtransaction tree,
 * so the main transaction will correctly recognize the flag if all
 * intermediate subtransactions commit.  When it is InvalidSubTransactionId,
 * we either haven't made the TEMP namespace yet, or have successfully
 * committed its creation, depending on whether myTempNamespace is valid.
 */
static Oid  myTempNamespace = InvalidOid;

static Oid  myTempToastNamespace = InvalidOid;

static SubTransactionId myTempNamespaceSubID = InvalidSubTransactionId;

/*
 * This is the user's textual search path specification --- it's the value
 * of the GUC variable 'search_path'.
 */
char     *namespace_search_path = NULL;


/* Local functions */
static bool RelationIsVisibleExt(Oid relid, bool *is_missing);
static bool TypeIsVisibleExt(Oid typid, bool *is_missing);
static bool FunctionIsVisibleExt(Oid funcid, bool *is_missing);
static bool OperatorIsVisibleExt(Oid oprid, bool *is_missing);
static bool OpclassIsVisibleExt(Oid opcid, bool *is_missing);
static bool OpfamilyIsVisibleExt(Oid opfid, bool *is_missing);
static bool CollationIsVisibleExt(Oid collid, bool *is_missing);
static bool ConversionIsVisibleExt(Oid conid, bool *is_missing);
static bool StatisticsObjIsVisibleExt(Oid stxid, bool *is_missing);
static bool TSParserIsVisibleExt(Oid prsId, bool *is_missing);
static bool TSDictionaryIsVisibleExt(Oid dictId, bool *is_missing);
static bool TSTemplateIsVisibleExt(Oid tmplId, bool *is_missing);
static bool TSConfigIsVisibleExt(Oid cfgid, bool *is_missing);
static void recomputeNamespacePath(void);
static void AccessTempTableNamespace(bool force);
static void InitTempTableNamespace(void);
static void RemoveTempRelations(Oid tempNamespaceId);
static void RemoveTempRelationsCallback(int code, Datum arg);
static void InvalidationCallback(Datum arg, int cacheid, uint32 hashvalue);
static bool MatchNamedCall(HeapTuple proctup, int nargs, List *argnames,
               bool include_out_arguments, int pronargs,
               int **argnumbers);

/*
 * Recomputing the namespace path can be costly when done frequently, such as
 * when a function has search_path set in proconfig. Add a search path cache
 * that can be used by recomputeNamespacePath().
 *
 * The cache is also used to remember already-validated strings in
 * check_search_path() to avoid the need to call SplitIdentifierString()
 * repeatedly.
 *
 * The search path cache is based on a wrapper around a simplehash hash table
 * (nsphash, defined below). The spcache wrapper deals with OOM while trying
 * to initialize a key, optimizes repeated lookups of the same key, and also
 * offers a more convenient API.
 */

static inline uint32
spcachekey_hash(SearchPathCacheKey key)
{
  fasthash_state hs;
  int     sp_len;

  fasthash_init(&hs, 0);

  hs.accum = key.roleid;
  fasthash_combine(&hs);

  /*
   * Combine search path into the hash and save the length for tweaking the
   * final mix.
   */
  sp_len = fasthash_accum_cstring(&hs, key.searchPath);

  return fasthash_final32(&hs, sp_len);
}

static inline bool
spcachekey_equal(SearchPathCacheKey a, SearchPathCacheKey b)
{
  return a.roleid == b.roleid &&
    strcmp(a.searchPath, b.searchPath) == 0;
}

#define SH_PREFIX   nsphash
#define SH_ELEMENT_TYPE SearchPathCacheEntry
#define SH_KEY_TYPE   SearchPathCacheKey
#define SH_KEY      key
#define SH_HASH_KEY(tb, key)    spcachekey_hash(key)
#define SH_EQUAL(tb, a, b)    spcachekey_equal(a, b)
#define SH_SCOPE    static inline
#define SH_DECLARE
#define SH_DEFINE
#include "lib/simplehash.h"

/*
 * We only expect a small number of unique search_path strings to be used. If
 * this cache grows to an unreasonable size, reset it to avoid steady-state
 * memory growth. Most likely, only a few of those entries will benefit from
 * the cache, and the cache will be quickly repopulated with such entries.
 */
#define SPCACHE_RESET_THRESHOLD   256

static nsphash_hash *SearchPathCache = NULL;
static SearchPathCacheEntry *LastSearchPathCacheEntry = NULL;

/*
 * Create or reset search_path cache as necessary.
 */
static void
spcache_init(void)
{
  if (SearchPathCache && searchPathCacheValid &&
    SearchPathCache->members < SPCACHE_RESET_THRESHOLD)
    return;

  searchPathCacheValid = false;
  baseSearchPathValid = false;

  /*
   * Make sure we don't leave dangling pointers if a failure happens during
   * initialization.
   */
  SearchPathCache = NULL;
  LastSearchPathCacheEntry = NULL;

  if (SearchPathCacheContext == NULL)
  {
    /* Make the context we'll keep search path cache hashtable in */
    SearchPathCacheContext = AllocSetContextCreate(TopMemoryContext,
                             "search_path processing cache",
                             ALLOCSET_DEFAULT_SIZES);
  }
  else
  {
    MemoryContextReset(SearchPathCacheContext);
  }

  /* arbitrary initial starting size of 16 elements */
  SearchPathCache = nsphash_create(SearchPathCacheContext, 16, NULL);
  searchPathCacheValid = true;
}

/*
 * Look up entry in search path cache without inserting. Returns NULL if not
 * present.
 */
static SearchPathCacheEntry *
spcache_lookup(const char *searchPath, Oid roleid)
{
  if (LastSearchPathCacheEntry &&
    LastSearchPathCacheEntry->key.roleid == roleid &&
    strcmp(LastSearchPathCacheEntry->key.searchPath, searchPath) == 0)
  {
    return LastSearchPathCacheEntry;
  }
  else
  {
    SearchPathCacheEntry *entry;
    SearchPathCacheKey cachekey = {
      .searchPath = searchPath,
      .roleid = roleid
    };

    entry = nsphash_lookup(SearchPathCache, cachekey);
    if (entry)
      LastSearchPathCacheEntry = entry;
    return entry;
  }
}

/*
 * Look up or insert entry in search path cache.
 *
 * Initialize key safely, so that OOM does not leave an entry without a valid
 * key. Caller must ensure that non-key contents are properly initialized.
 */
static SearchPathCacheEntry *
spcache_insert(const char *searchPath, Oid roleid)
{
  if (LastSearchPathCacheEntry &&
    LastSearchPathCacheEntry->key.roleid == roleid &&
    strcmp(LastSearchPathCacheEntry->key.searchPath, searchPath) == 0)
  {
    return LastSearchPathCacheEntry;
  }
  else
  {
    SearchPathCacheEntry *entry;
    SearchPathCacheKey cachekey = {
      .searchPath = searchPath,
      .roleid = roleid
    };

    /*
     * searchPath is not saved in SearchPathCacheContext. First perform a
     * lookup, and copy searchPath only if we need to create a new entry.
     */
    entry = nsphash_lookup(SearchPathCache, cachekey);

    if (!entry)
    {
      bool    found;

      cachekey.searchPath = MemoryContextStrdup(SearchPathCacheContext, searchPath);
      entry = nsphash_insert(SearchPathCache, cachekey, &found);
      Assert(!found);

      entry->oidlist = NIL;
      entry->finalPath = NIL;
      entry->firstNS = InvalidOid;
      entry->temp_missing = false;
      entry->forceRecompute = false;
      /* do not touch entry->status, used by simplehash */
    }

    LastSearchPathCacheEntry = entry;
    return entry;
  }
}

/*
 * RangeVarGetRelidExtended
 *    Given a RangeVar describing an existing relation,
 *    select the proper namespace and look up the relation OID.
 *
 * If the schema or relation is not found, return InvalidOid if flags contains
 * RVR_MISSING_OK, otherwise raise an error.
 *
 * If flags contains RVR_NOWAIT, throw an error if we'd have to wait for a
 * lock.
 *
 * If flags contains RVR_SKIP_LOCKED, return InvalidOid if we'd have to wait
 * for a lock.
 *
 * flags cannot contain both RVR_NOWAIT and RVR_SKIP_LOCKED.
 *
 * Note that if RVR_MISSING_OK and RVR_SKIP_LOCKED are both specified, a
 * return value of InvalidOid could either mean the relation is missing or it
 * could not be locked.
 *
 * Callback allows caller to check permissions or acquire additional locks
 * prior to grabbing the relation lock.
 */
Oid
RangeVarGetRelidExtended(const RangeVar *relation, LOCKMODE lockmode,
             uint32 flags,
             RangeVarGetRelidCallback callback, void *callback_arg)
{
  uint64    inval_count;
  Oid     relId;
  Oid     oldRelId = InvalidOid;
  bool    retry = false;
  bool    missing_ok = (flags & RVR_MISSING_OK) != 0;

  /* verify that flags do no conflict */
  Assert(!((flags & RVR_NOWAIT) && (flags & RVR_SKIP_LOCKED)));

  /*
   * We check the catalog name and then ignore it.
   */
  if (relation->catalogname)
  {
    if (strcmp(relation->catalogname, get_database_name(MyDatabaseId)) != 0)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("cross-database references are not implemented: \"%s.%s.%s\"",
              relation->catalogname, relation->schemaname,
              relation->relname)));
  }

  /*
   * DDL operations can change the results of a name lookup.  Since all such
   * operations will generate invalidation messages, we keep track of
   * whether any such messages show up while we're performing the operation,
   * and retry until either (1) no more invalidation messages show up or (2)
   * the answer doesn't change.
   *
   * But if lockmode = NoLock, then we assume that either the caller is OK
   * with the answer changing under them, or that they already hold some
   * appropriate lock, and therefore return the first answer we get without
   * checking for invalidation messages.  Also, if the requested lock is
   * already held, LockRelationOid will not AcceptInvalidationMessages, so
   * we may fail to notice a change.  We could protect against that case by
   * calling AcceptInvalidationMessages() before beginning this loop, but
   * that would add a significant amount overhead, so for now we don't.
   */
  for (;;)
  {
    /*
     * Remember this value, so that, after looking up the relation name
     * and locking its OID, we can check whether any invalidation messages
     * have been processed that might require a do-over.
     */
    inval_count = SharedInvalidMessageCounter;

    /*
     * Some non-default relpersistence value may have been specified.  The
     * parser never generates such a RangeVar in simple DML, but it can
     * happen in contexts such as "CREATE TEMP TABLE foo (f1 int PRIMARY
     * KEY)".  Such a command will generate an added CREATE INDEX
     * operation, which must be careful to find the temp table, even when
     * pg_temp is not first in the search path.
     */
    if (relation->relpersistence == RELPERSISTENCE_TEMP)
    {
      if (!OidIsValid(myTempNamespace))
        relId = InvalidOid; /* this probably can't happen? */
      else
      {
        if (relation->schemaname)
        {
          Oid     namespaceId;

          namespaceId = LookupExplicitNamespace(relation->schemaname, missing_ok);

          /*
           * For missing_ok, allow a non-existent schema name to
           * return InvalidOid.
           */
          if (namespaceId != myTempNamespace)
            ereport(ERROR,
                (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
                 errmsg("temporary tables cannot specify a schema name")));
        }

        relId = get_relname_relid(relation->relname, myTempNamespace);
      }
    }
    else if (relation->schemaname)
    {
      Oid     namespaceId;

      /* use exact schema given */
      namespaceId = LookupExplicitNamespace(relation->schemaname, missing_ok);
      if (missing_ok && !OidIsValid(namespaceId))
        relId = InvalidOid;
      else
        relId = get_relname_relid(relation->relname, namespaceId);
    }
    else
    {
      /* search the namespace path */
      relId = RelnameGetRelid(relation->relname);
    }

    /*
     * Invoke caller-supplied callback, if any.
     *
     * This callback is a good place to check permissions: we haven't
     * taken the table lock yet (and it's really best to check permissions
     * before locking anything!), but we've gotten far enough to know what
     * OID we think we should lock.  Of course, concurrent DDL might
     * change things while we're waiting for the lock, but in that case
     * the callback will be invoked again for the new OID.
     */
    if (callback)
      callback(relation, relId, oldRelId, callback_arg);

    /*
     * If no lock requested, we assume the caller knows what they're
     * doing.  They should have already acquired a heavyweight lock on
     * this relation earlier in the processing of this same statement, so
     * it wouldn't be appropriate to AcceptInvalidationMessages() here, as
     * that might pull the rug out from under them.
     */
    if (lockmode == NoLock)
      break;

    /*
     * If, upon retry, we get back the same OID we did last time, then the
     * invalidation messages we processed did not change the final answer.
     * So we're done.
     *
     * If we got a different OID, we've locked the relation that used to
     * have this name rather than the one that does now.  So release the
     * lock.
     */
    if (retry)
    {
      if (relId == oldRelId)
        break;
      if (OidIsValid(oldRelId))
        UnlockRelationOid(oldRelId, lockmode);
    }

    /*
     * Lock relation.  This will also accept any pending invalidation
     * messages.  If we got back InvalidOid, indicating not found, then
     * there's nothing to lock, but we accept invalidation messages
     * anyway, to flush any negative catcache entries that may be
     * lingering.
     */
    if (!OidIsValid(relId))
      AcceptInvalidationMessages();
    else if (!(flags & (RVR_NOWAIT | RVR_SKIP_LOCKED)))
      LockRelationOid(relId, lockmode);
    else if (!ConditionalLockRelationOid(relId, lockmode))
    {
      int     elevel = (flags & RVR_SKIP_LOCKED) ? DEBUG1 : ERROR;

      if (relation->schemaname)
        ereport(elevel,
            (errcode(ERRCODE_LOCK_NOT_AVAILABLE),
             errmsg("could not obtain lock on relation \"%s.%s\"",
                relation->schemaname, relation->relname)));
      else
        ereport(elevel,
            (errcode(ERRCODE_LOCK_NOT_AVAILABLE),
             errmsg("could not obtain lock on relation \"%s\"",
                relation->relname)));

      return InvalidOid;
    }

    /*
     * If no invalidation message were processed, we're done!
     */
    if (inval_count == SharedInvalidMessageCounter)
      break;

    /*
     * Something may have changed.  Let's repeat the name lookup, to make
     * sure this name still references the same relation it did
     * previously.
     */
    retry = true;
    oldRelId = relId;
  }

  if (!OidIsValid(relId))
  {
    int     elevel = missing_ok ? DEBUG1 : ERROR;

    if (relation->schemaname)
      ereport(elevel,
          (errcode(ERRCODE_UNDEFINED_TABLE),
           errmsg("relation \"%s.%s\" does not exist",
              relation->schemaname, relation->relname)));
    else
      ereport(elevel,
          (errcode(ERRCODE_UNDEFINED_TABLE),
           errmsg("relation \"%s\" does not exist",
              relation->relname)));
  }
  return relId;
}

/*
 * RangeVarGetCreationNamespace
 *    Given a RangeVar describing a to-be-created relation,
 *    choose which namespace to create it in.
 *
 * Note: calling this may result in a CommandCounterIncrement operation.
 * That will happen on the first request for a temp table in any particular
 * backend run; we will need to either create or clean out the temp schema.
 */
Oid
RangeVarGetCreationNamespace(const RangeVar *newRelation)
{
  Oid     namespaceId;

  /*
   * We check the catalog name and then ignore it.
   */
  if (newRelation->catalogname)
  {
    if (strcmp(newRelation->catalogname, get_database_name(MyDatabaseId)) != 0)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("cross-database references are not implemented: \"%s.%s.%s\"",
              newRelation->catalogname, newRelation->schemaname,
              newRelation->relname)));
  }

  if (newRelation->schemaname)
  {
    /* check for pg_temp alias */
    if (strcmp(newRelation->schemaname, "pg_temp") == 0)
    {
      /* Initialize temp namespace */
      AccessTempTableNamespace(false);
      return myTempNamespace;
    }
    /* use exact schema given */
    namespaceId = get_namespace_oid(newRelation->schemaname, false);
    /* we do not check for USAGE rights here! */
  }
  else if (newRelation->relpersistence == RELPERSISTENCE_TEMP)
  {
    /* Initialize temp namespace */
    AccessTempTableNamespace(false);
    return myTempNamespace;
  }
  else
  {
    /* use the default creation namespace */
    recomputeNamespacePath();
    if (activeTempCreationPending)
    {
      /* Need to initialize temp namespace */
      AccessTempTableNamespace(true);
      return myTempNamespace;
    }
    namespaceId = activeCreationNamespace;
    if (!OidIsValid(namespaceId))
      ereport(ERROR,
          (errcode(ERRCODE_UNDEFINED_SCHEMA),
           errmsg("no schema has been selected to create in")));
  }

  /* Note: callers will check for CREATE rights when appropriate */

  return namespaceId;
}

/*
 * RangeVarGetAndCheckCreationNamespace
 *
 * This function returns the OID of the namespace in which a new relation
 * with a given name should be created.  If the user does not have CREATE
 * permission on the target namespace, this function will instead signal
 * an ERROR.
 *
 * If non-NULL, *existing_relation_id is set to the OID of any existing relation
 * with the same name which already exists in that namespace, or to InvalidOid
 * if no such relation exists.
 *
 * If lockmode != NoLock, the specified lock mode is acquired on the existing
 * relation, if any, provided that the current user owns the target relation.
 * However, if lockmode != NoLock and the user does not own the target
 * relation, we throw an ERROR, as we must not try to lock relations the
 * user does not have permissions on.
 *
 * As a side effect, this function acquires AccessShareLock on the target
 * namespace.  Without this, the namespace could be dropped before our
 * transaction commits, leaving behind relations with relnamespace pointing
 * to a no-longer-existent namespace.
 *
 * As a further side-effect, if the selected namespace is a temporary namespace,
 * we mark the RangeVar as RELPERSISTENCE_TEMP.
 */
Oid
RangeVarGetAndCheckCreationNamespace(RangeVar *relation,
                   LOCKMODE lockmode,
                   Oid *existing_relation_id)
{
  uint64    inval_count;
  Oid     relid;
  Oid     oldrelid = InvalidOid;
  Oid     nspid;
  Oid     oldnspid = InvalidOid;
  bool    retry = false;

  /*
   * We check the catalog name and then ignore it.
   */
  if (relation->catalogname)
  {
    if (strcmp(relation->catalogname, get_database_name(MyDatabaseId)) != 0)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("cross-database references are not implemented: \"%s.%s.%s\"",
              relation->catalogname, relation->schemaname,
              relation->relname)));
  }

  /*
   * As in RangeVarGetRelidExtended(), we guard against concurrent DDL
   * operations by tracking whether any invalidation messages are processed
   * while we're doing the name lookups and acquiring locks.  See comments
   * in that function for a more detailed explanation of this logic.
   */
  for (;;)
  {
    AclResult aclresult;

    inval_count = SharedInvalidMessageCounter;

    /* Look up creation namespace and check for existing relation. */
    nspid = RangeVarGetCreationNamespace(relation);
    Assert(OidIsValid(nspid));
    if (existing_relation_id != NULL)
      relid = get_relname_relid(relation->relname, nspid);
    else
      relid = InvalidOid;

    /*
     * In bootstrap processing mode, we don't bother with permissions or
     * locking.  Permissions might not be working yet, and locking is
     * unnecessary.
     */
    if (IsBootstrapProcessingMode())
      break;

    /* Check namespace permissions. */
    aclresult = object_aclcheck(NamespaceRelationId, nspid, GetUserId(), ACL_CREATE);
    if (aclresult != ACLCHECK_OK)
      aclcheck_error(aclresult, OBJECT_SCHEMA,
               get_namespace_name(nspid));

    if (retry)
    {
      /* If nothing changed, we're done. */
      if (relid == oldrelid && nspid == oldnspid)
        break;
      /* If creation namespace has changed, give up old lock. */
      if (nspid != oldnspid)
        UnlockDatabaseObject(NamespaceRelationId, oldnspid, 0,
                   AccessShareLock);
      /* If name points to something different, give up old lock. */
      if (relid != oldrelid && OidIsValid(oldrelid) && lockmode != NoLock)
        UnlockRelationOid(oldrelid, lockmode);
    }

    /* Lock namespace. */
    if (nspid != oldnspid)
      LockDatabaseObject(NamespaceRelationId, nspid, 0, AccessShareLock);

    /* Lock relation, if required if and we have permission. */
    if (lockmode != NoLock && OidIsValid(relid))
    {
      if (!object_ownercheck(RelationRelationId, relid, GetUserId()))
        aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relid)),
                 relation->relname);
      if (relid != oldrelid)
        LockRelationOid(relid, lockmode);
    }

    /* If no invalidation message were processed, we're done! */
    if (inval_count == SharedInvalidMessageCounter)
      break;

    /* Something may have changed, so recheck our work. */
    retry = true;
    oldrelid = relid;
    oldnspid = nspid;
  }

  RangeVarAdjustRelationPersistence(relation, nspid);
  if (existing_relation_id != NULL)
    *existing_relation_id = relid;
  return nspid;
}

/*
 * Adjust the relpersistence for an about-to-be-created relation based on the
 * creation namespace, and throw an error for invalid combinations.
 */
void
RangeVarAdjustRelationPersistence(RangeVar *newRelation, Oid nspid)
{
  switch (newRelation->relpersistence)
  {
    case RELPERSISTENCE_TEMP:
      if (!isTempOrTempToastNamespace(nspid))
      {
        if (isAnyTempNamespace(nspid))
          ereport(ERROR,
              (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
               errmsg("cannot create relations in temporary schemas of other sessions")));
        else
          ereport(ERROR,
              (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
               errmsg("cannot create temporary relation in non-temporary schema")));
      }
      break;
    case RELPERSISTENCE_PERMANENT:
      if (isTempOrTempToastNamespace(nspid))
        newRelation->relpersistence = RELPERSISTENCE_TEMP;
      else if (isAnyTempNamespace(nspid))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
             errmsg("cannot create relations in temporary schemas of other sessions")));
      break;
    default:
      if (isAnyTempNamespace(nspid))
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
             errmsg("only temporary relations may be created in temporary schemas")));
  }
}

/*
 * RelnameGetRelid
 *    Try to resolve an unqualified relation name.
 *    Returns OID if relation found in search path, else InvalidOid.
 */
Oid
RelnameGetRelid(const char *relname)
{
  Oid     relid;
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);

    relid = get_relname_relid(relname, namespaceId);
    if (OidIsValid(relid))
      return relid;
  }

  /* Not found in path */
  return InvalidOid;
}


/*
 * RelationIsVisible
 *    Determine whether a relation (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified relation name".
 */
bool
RelationIsVisible(Oid relid)
{
  return RelationIsVisibleExt(relid, NULL);
}

/*
 * RelationIsVisibleExt
 *    As above, but if the relation isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
RelationIsVisibleExt(Oid relid, bool *is_missing)
{
  HeapTuple reltup;
  Form_pg_class relform;
  Oid     relnamespace;
  bool    visible;

  reltup = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
  if (!HeapTupleIsValid(reltup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for relation %u", relid);
  }
  relform = (Form_pg_class) GETSTRUCT(reltup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  relnamespace = relform->relnamespace;
  if (relnamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, relnamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another relation of the same name earlier in the path. So
     * we must do a slow check for conflicting relations.
     */
    char     *relname = NameStr(relform->relname);
    ListCell   *l;

    visible = false;
    foreach(l, activeSearchPath)
    {
      Oid     namespaceId = lfirst_oid(l);

      if (namespaceId == relnamespace)
      {
        /* Found it first in path */
        visible = true;
        break;
      }
      if (OidIsValid(get_relname_relid(relname, namespaceId)))
      {
        /* Found something else first in path */
        break;
      }
    }
  }

  ReleaseSysCache(reltup);

  return visible;
}


/*
 * TypenameGetTypid
 *    Wrapper for binary compatibility.
 */
Oid
TypenameGetTypid(const char *typname)
{
  return TypenameGetTypidExtended(typname, true);
}

/*
 * TypenameGetTypidExtended
 *    Try to resolve an unqualified datatype name.
 *    Returns OID if type found in search path, else InvalidOid.
 *
 * This is essentially the same as RelnameGetRelid.
 */
Oid
TypenameGetTypidExtended(const char *typname, bool temp_ok)
{
  Oid     typid;
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);

    if (!temp_ok && namespaceId == myTempNamespace)
      continue;     /* do not look in temp namespace */

    typid = GetSysCacheOid2(TYPENAMENSP, Anum_pg_type_oid,
                PointerGetDatum(typname),
                ObjectIdGetDatum(namespaceId));
    if (OidIsValid(typid))
      return typid;
  }

  /* Not found in path */
  return InvalidOid;
}

/*
 * TypeIsVisible
 *    Determine whether a type (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified type name".
 */
bool
TypeIsVisible(Oid typid)
{
  return TypeIsVisibleExt(typid, NULL);
}

/*
 * TypeIsVisibleExt
 *    As above, but if the type isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
TypeIsVisibleExt(Oid typid, bool *is_missing)
{
  HeapTuple typtup;
  Form_pg_type typform;
  Oid     typnamespace;
  bool    visible;

  typtup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
  if (!HeapTupleIsValid(typtup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for type %u", typid);
  }
  typform = (Form_pg_type) GETSTRUCT(typtup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  typnamespace = typform->typnamespace;
  if (typnamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, typnamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another type of the same name earlier in the path. So we
     * must do a slow check for conflicting types.
     */
    char     *typname = NameStr(typform->typname);
    ListCell   *l;

    visible = false;
    foreach(l, activeSearchPath)
    {
      Oid     namespaceId = lfirst_oid(l);

      if (namespaceId == typnamespace)
      {
        /* Found it first in path */
        visible = true;
        break;
      }
      if (SearchSysCacheExists2(TYPENAMENSP,
                    PointerGetDatum(typname),
                    ObjectIdGetDatum(namespaceId)))
      {
        /* Found something else first in path */
        break;
      }
    }
  }

  ReleaseSysCache(typtup);

  return visible;
}


/*
 * FuncnameGetCandidates
 *    Given a possibly-qualified function name and argument count,
 *    retrieve a list of the possible matches.
 *
 * If nargs is -1, we return all functions matching the given name,
 * regardless of argument count.  (argnames must be NIL, and expand_variadic
 * and expand_defaults must be false, in this case.)
 *
 * If argnames isn't NIL, we are considering a named- or mixed-notation call,
 * and only functions having all the listed argument names will be returned.
 * (We assume that length(argnames) <= nargs and all the passed-in names are
 * distinct.)  The returned structs will include an argnumbers array showing
 * the actual argument index for each logical argument position.
 *
 * If expand_variadic is true, then variadic functions having the same number
 * or fewer arguments will be retrieved, with the variadic argument and any
 * additional argument positions filled with the variadic element type.
 * nvargs in the returned struct is set to the number of such arguments.
 * If expand_variadic is false, variadic arguments are not treated specially,
 * and the returned nvargs will always be zero.
 *
 * If expand_defaults is true, functions that could match after insertion of
 * default argument values will also be retrieved.  In this case the returned
 * structs could have nargs > passed-in nargs, and ndargs is set to the number
 * of additional args (which can be retrieved from the function's
 * proargdefaults entry).
 *
 * If include_out_arguments is true, then OUT-mode arguments are considered to
 * be included in the argument list.  Their types are included in the returned
 * arrays, and argnumbers are indexes in proallargtypes not proargtypes.
 * We also set nominalnargs to be the length of proallargtypes not proargtypes.
 * Otherwise OUT-mode arguments are ignored.
 *
 * It is not possible for nvargs and ndargs to both be nonzero in the same
 * list entry, since default insertion allows matches to functions with more
 * than nargs arguments while the variadic transformation requires the same
 * number or less.
 *
 * When argnames isn't NIL, the returned args[] type arrays are not ordered
 * according to the functions' declarations, but rather according to the call:
 * first any positional arguments, then the named arguments, then defaulted
 * arguments (if needed and allowed by expand_defaults).  The argnumbers[]
 * array can be used to map this back to the catalog information.
 * argnumbers[k] is set to the proargtypes or proallargtypes index of the
 * k'th call argument.
 *
 * We search a single namespace if the function name is qualified, else
 * all namespaces in the search path.  In the multiple-namespace case,
 * we arrange for entries in earlier namespaces to mask identical entries in
 * later namespaces.
 *
 * When expanding variadics, we arrange for non-variadic functions to mask
 * variadic ones if the expanded argument list is the same.  It is still
 * possible for there to be conflicts between different variadic functions,
 * however.
 *
 * It is guaranteed that the return list will never contain multiple entries
 * with identical argument lists.  When expand_defaults is true, the entries
 * could have more than nargs positions, but we still guarantee that they are
 * distinct in the first nargs positions.  However, if argnames isn't NIL or
 * either expand_variadic or expand_defaults is true, there might be multiple
 * candidate functions that expand to identical argument lists.  Rather than
 * throw error here, we report such situations by returning a single entry
 * with oid = 0 that represents a set of such conflicting candidates.
 * The caller might end up discarding such an entry anyway, but if it selects
 * such an entry it should react as though the call were ambiguous.
 *
 * If missing_ok is true, an empty list (NULL) is returned if the name was
 * schema-qualified with a schema that does not exist.  Likewise if no
 * candidate is found for other reasons.
 */
FuncCandidateList
FuncnameGetCandidates(List *names, int nargs, List *argnames,
            bool expand_variadic, bool expand_defaults,
            bool include_out_arguments, bool missing_ok)
{
  FuncCandidateList resultList = NULL;
  bool    any_special = false;
  char     *schemaname;
  char     *funcname;
  Oid     namespaceId;
  CatCList   *catlist;
  int     i;

  /* check for caller error */
  Assert(nargs >= 0 || !(expand_variadic | expand_defaults));

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &funcname);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (!OidIsValid(namespaceId))
      return NULL;
  }
  else
  {
    /* flag to indicate we need namespace search */
    namespaceId = InvalidOid;
    recomputeNamespacePath();
  }

  /* Search syscache by name only */
  catlist = SearchSysCacheList1(PROCNAMEARGSNSP, CStringGetDatum(funcname));

  for (i = 0; i < catlist->n_members; i++)
  {
    HeapTuple proctup = &catlist->members[i]->tuple;
    Form_pg_proc procform = (Form_pg_proc) GETSTRUCT(proctup);
    Oid      *proargtypes = procform->proargtypes.values;
    int     pronargs = procform->pronargs;
    int     effective_nargs;
    int     pathpos = 0;
    bool    variadic;
    bool    use_defaults;
    Oid     va_elem_type;
    int      *argnumbers = NULL;
    FuncCandidateList newResult;

    if (OidIsValid(namespaceId))
    {
      /* Consider only procs in specified namespace */
      if (procform->pronamespace != namespaceId)
        continue;
    }
    else
    {
      /*
       * Consider only procs that are in the search path and are not in
       * the temp namespace.
       */
      ListCell   *nsp;

      foreach(nsp, activeSearchPath)
      {
        if (procform->pronamespace == lfirst_oid(nsp) &&
          procform->pronamespace != myTempNamespace)
          break;
        pathpos++;
      }
      if (nsp == NULL)
        continue;   /* proc is not in search path */
    }

    /*
     * If we are asked to match to OUT arguments, then use the
     * proallargtypes array (which includes those); otherwise use
     * proargtypes (which doesn't).  Of course, if proallargtypes is null,
     * we always use proargtypes.
     */
    if (include_out_arguments)
    {
      Datum   proallargtypes;
      bool    isNull;

      proallargtypes = SysCacheGetAttr(PROCNAMEARGSNSP, proctup,
                       Anum_pg_proc_proallargtypes,
                       &isNull);
      if (!isNull)
      {
        ArrayType  *arr = DatumGetArrayTypeP(proallargtypes);

        pronargs = ARR_DIMS(arr)[0];
        if (ARR_NDIM(arr) != 1 ||
          pronargs < 0 ||
          ARR_HASNULL(arr) ||
          ARR_ELEMTYPE(arr) != OIDOID)
          elog(ERROR, "proallargtypes is not a 1-D Oid array or it contains nulls");
        Assert(pronargs >= procform->pronargs);
        proargtypes = (Oid *) ARR_DATA_PTR(arr);
      }
    }

    if (argnames != NIL)
    {
      /*
       * Call uses named or mixed notation
       *
       * Named or mixed notation can match a variadic function only if
       * expand_variadic is off; otherwise there is no way to match the
       * presumed-nameless parameters expanded from the variadic array.
       */
      if (OidIsValid(procform->provariadic) && expand_variadic)
        continue;
      va_elem_type = InvalidOid;
      variadic = false;

      /*
       * Check argument count.
       */
      Assert(nargs >= 0); /* -1 not supported with argnames */

      if (pronargs > nargs && expand_defaults)
      {
        /* Ignore if not enough default expressions */
        if (nargs + procform->pronargdefaults < pronargs)
          continue;
        use_defaults = true;
      }
      else
        use_defaults = false;

      /* Ignore if it doesn't match requested argument count */
      if (pronargs != nargs && !use_defaults)
        continue;

      /* Check for argument name match, generate positional mapping */
      if (!MatchNamedCall(proctup, nargs, argnames,
                include_out_arguments, pronargs,
                &argnumbers))
        continue;

      /* Named argument matching is always "special" */
      any_special = true;
    }
    else
    {
      /*
       * Call uses positional notation
       *
       * Check if function is variadic, and get variadic element type if
       * so.  If expand_variadic is false, we should just ignore
       * variadic-ness.
       */
      if (pronargs <= nargs && expand_variadic)
      {
        va_elem_type = procform->provariadic;
        variadic = OidIsValid(va_elem_type);
        any_special |= variadic;
      }
      else
      {
        va_elem_type = InvalidOid;
        variadic = false;
      }

      /*
       * Check if function can match by using parameter defaults.
       */
      if (pronargs > nargs && expand_defaults)
      {
        /* Ignore if not enough default expressions */
        if (nargs + procform->pronargdefaults < pronargs)
          continue;
        use_defaults = true;
        any_special = true;
      }
      else
        use_defaults = false;

      /* Ignore if it doesn't match requested argument count */
      if (nargs >= 0 && pronargs != nargs && !variadic && !use_defaults)
        continue;
    }

    /*
     * We must compute the effective argument list so that we can easily
     * compare it to earlier results.  We waste a palloc cycle if it gets
     * masked by an earlier result, but really that's a pretty infrequent
     * case so it's not worth worrying about.
     */
    effective_nargs = Max(pronargs, nargs);
    newResult = (FuncCandidateList)
      palloc(offsetof(struct _FuncCandidateList, args) +
           effective_nargs * sizeof(Oid));
    newResult->pathpos = pathpos;
    newResult->oid = procform->oid;
    newResult->nominalnargs = pronargs;
    newResult->nargs = effective_nargs;
    newResult->argnumbers = argnumbers;
    if (argnumbers)
    {
      /* Re-order the argument types into call's logical order */
      for (int j = 0; j < pronargs; j++)
        newResult->args[j] = proargtypes[argnumbers[j]];
    }
    else
    {
      /* Simple positional case, just copy proargtypes as-is */
      memcpy(newResult->args, proargtypes, pronargs * sizeof(Oid));
    }
    if (variadic)
    {
      newResult->nvargs = effective_nargs - pronargs + 1;
      /* Expand variadic argument into N copies of element type */
      for (int j = pronargs - 1; j < effective_nargs; j++)
        newResult->args[j] = va_elem_type;
    }
    else
      newResult->nvargs = 0;
    newResult->ndargs = use_defaults ? pronargs - nargs : 0;

    /*
     * Does it have the same arguments as something we already accepted?
     * If so, decide what to do to avoid returning duplicate argument
     * lists.  We can skip this check for the single-namespace case if no
     * special (named, variadic or defaults) match has been made, since
     * then the unique index on pg_proc guarantees all the matches have
     * different argument lists.
     */
    if (resultList != NULL &&
      (any_special || !OidIsValid(namespaceId)))
    {
      /*
       * If we have an ordered list from SearchSysCacheList (the normal
       * case), then any conflicting proc must immediately adjoin this
       * one in the list, so we only need to look at the newest result
       * item.  If we have an unordered list, we have to scan the whole
       * result list.  Also, if either the current candidate or any
       * previous candidate is a special match, we can't assume that
       * conflicts are adjacent.
       *
       * We ignore defaulted arguments in deciding what is a match.
       */
      FuncCandidateList prevResult;

      if (catlist->ordered && !any_special)
      {
        /* ndargs must be 0 if !any_special */
        if (effective_nargs == resultList->nargs &&
          memcmp(newResult->args,
               resultList->args,
               effective_nargs * sizeof(Oid)) == 0)
          prevResult = resultList;
        else
          prevResult = NULL;
      }
      else
      {
        int     cmp_nargs = newResult->nargs - newResult->ndargs;

        for (prevResult = resultList;
           prevResult;
           prevResult = prevResult->next)
        {
          if (cmp_nargs == prevResult->nargs - prevResult->ndargs &&
            memcmp(newResult->args,
                 prevResult->args,
                 cmp_nargs * sizeof(Oid)) == 0)
            break;
        }
      }

      if (prevResult)
      {
        /*
         * We have a match with a previous result.  Decide which one
         * to keep, or mark it ambiguous if we can't decide.  The
         * logic here is preference > 0 means prefer the old result,
         * preference < 0 means prefer the new, preference = 0 means
         * ambiguous.
         */
        int     preference;

        if (pathpos != prevResult->pathpos)
        {
          /*
           * Prefer the one that's earlier in the search path.
           */
          preference = pathpos - prevResult->pathpos;
        }
        else if (variadic && prevResult->nvargs == 0)
        {
          /*
           * With variadic functions we could have, for example,
           * both foo(numeric) and foo(variadic numeric[]) in the
           * same namespace; if so we prefer the non-variadic match
           * on efficiency grounds.
           */
          preference = 1;
        }
        else if (!variadic && prevResult->nvargs > 0)
        {
          preference = -1;
        }
        else
        {
          /*----------
           * We can't decide.  This can happen with, for example,
           * both foo(numeric, variadic numeric[]) and
           * foo(variadic numeric[]) in the same namespace, or
           * both foo(int) and foo (int, int default something)
           * in the same namespace, or both foo(a int, b text)
           * and foo(b text, a int) in the same namespace.
           *----------
           */
          preference = 0;
        }

        if (preference > 0)
        {
          /* keep previous result */
          pfree(newResult);
          continue;
        }
        else if (preference < 0)
        {
          /* remove previous result from the list */
          if (prevResult == resultList)
            resultList = prevResult->next;
          else
          {
            FuncCandidateList prevPrevResult;

            for (prevPrevResult = resultList;
               prevPrevResult;
               prevPrevResult = prevPrevResult->next)
            {
              if (prevResult == prevPrevResult->next)
              {
                prevPrevResult->next = prevResult->next;
                break;
              }
            }
            Assert(prevPrevResult); /* assert we found it */
          }
          pfree(prevResult);
          /* fall through to add newResult to list */
        }
        else
        {
          /* mark old result as ambiguous, discard new */
          prevResult->oid = InvalidOid;
          pfree(newResult);
          continue;
        }
      }
    }

    /*
     * Okay to add it to result list
     */
    newResult->next = resultList;
    resultList = newResult;
  }

  ReleaseSysCacheList(catlist);

  return resultList;
}

/*
 * MatchNamedCall
 *    Given a pg_proc heap tuple and a call's list of argument names,
 *    check whether the function could match the call.
 *
 * The call could match if all supplied argument names are accepted by
 * the function, in positions after the last positional argument, and there
 * are defaults for all unsupplied arguments.
 *
 * If include_out_arguments is true, we are treating OUT arguments as
 * included in the argument list.  pronargs is the number of arguments
 * we're considering (the length of either proargtypes or proallargtypes).
 *
 * The number of positional arguments is nargs - list_length(argnames).
 * Note caller has already done basic checks on argument count.
 *
 * On match, return true and fill *argnumbers with a palloc'd array showing
 * the mapping from call argument positions to actual function argument
 * numbers.  Defaulted arguments are included in this map, at positions
 * after the last supplied argument.
 */
static bool
MatchNamedCall(HeapTuple proctup, int nargs, List *argnames,
         bool include_out_arguments, int pronargs,
         int **argnumbers)
{
  Form_pg_proc procform = (Form_pg_proc) GETSTRUCT(proctup);
  int     numposargs = nargs - list_length(argnames);
  int     pronallargs;
  Oid      *p_argtypes;
  char    **p_argnames;
  char     *p_argmodes;
  bool    arggiven[FUNC_MAX_ARGS];
  bool    isnull;
  int     ap;       /* call args position */
  int     pp;       /* proargs position */
  ListCell   *lc;

  Assert(argnames != NIL);
  Assert(numposargs >= 0);
  Assert(nargs <= pronargs);

  /* Ignore this function if its proargnames is null */
  (void) SysCacheGetAttr(PROCOID, proctup, Anum_pg_proc_proargnames,
               &isnull);
  if (isnull)
    return false;

  /* OK, let's extract the argument names and types */
  pronallargs = get_func_arg_info(proctup,
                  &p_argtypes, &p_argnames, &p_argmodes);
  Assert(p_argnames != NULL);

  Assert(include_out_arguments ? (pronargs == pronallargs) : (pronargs <= pronallargs));

  /* initialize state for matching */
  *argnumbers = (int *) palloc(pronargs * sizeof(int));
  memset(arggiven, false, pronargs * sizeof(bool));

  /* there are numposargs positional args before the named args */
  for (ap = 0; ap < numposargs; ap++)
  {
    (*argnumbers)[ap] = ap;
    arggiven[ap] = true;
  }

  /* now examine the named args */
  foreach(lc, argnames)
  {
    char     *argname = (char *) lfirst(lc);
    bool    found;
    int     i;

    pp = 0;
    found = false;
    for (i = 0; i < pronallargs; i++)
    {
      /* consider only input params, except with include_out_arguments */
      if (!include_out_arguments &&
        p_argmodes &&
        (p_argmodes[i] != FUNC_PARAM_IN &&
         p_argmodes[i] != FUNC_PARAM_INOUT &&
         p_argmodes[i] != FUNC_PARAM_VARIADIC))
        continue;
      if (p_argnames[i] && strcmp(p_argnames[i], argname) == 0)
      {
        /* fail if argname matches a positional argument */
        if (arggiven[pp])
          return false;
        arggiven[pp] = true;
        (*argnumbers)[ap] = pp;
        found = true;
        break;
      }
      /* increase pp only for considered parameters */
      pp++;
    }
    /* if name isn't in proargnames, fail */
    if (!found)
      return false;
    ap++;
  }

  Assert(ap == nargs);    /* processed all actual parameters */

  /* Check for default arguments */
  if (nargs < pronargs)
  {
    int     first_arg_with_default = pronargs - procform->pronargdefaults;

    for (pp = numposargs; pp < pronargs; pp++)
    {
      if (arggiven[pp])
        continue;
      /* fail if arg not given and no default available */
      if (pp < first_arg_with_default)
        return false;
      (*argnumbers)[ap++] = pp;
    }
  }

  Assert(ap == pronargs);   /* processed all function parameters */

  return true;
}

/*
 * FunctionIsVisible
 *    Determine whether a function (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified function name with exact argument matches".
 */
bool
FunctionIsVisible(Oid funcid)
{
  return FunctionIsVisibleExt(funcid, NULL);
}

/*
 * FunctionIsVisibleExt
 *    As above, but if the function isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
FunctionIsVisibleExt(Oid funcid, bool *is_missing)
{
  HeapTuple proctup;
  Form_pg_proc procform;
  Oid     pronamespace;
  bool    visible;

  proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
  if (!HeapTupleIsValid(proctup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for function %u", funcid);
  }
  procform = (Form_pg_proc) GETSTRUCT(proctup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  pronamespace = procform->pronamespace;
  if (pronamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, pronamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another proc of the same name and arguments earlier in
     * the path.  So we must do a slow check to see if this is the same
     * proc that would be found by FuncnameGetCandidates.
     */
    char     *proname = NameStr(procform->proname);
    int     nargs = procform->pronargs;
    FuncCandidateList clist;

    visible = false;

    clist = FuncnameGetCandidates(list_make1(makeString(proname)),
                    nargs, NIL, false, false, false, false);

    for (; clist; clist = clist->next)
    {
      if (memcmp(clist->args, procform->proargtypes.values,
             nargs * sizeof(Oid)) == 0)
      {
        /* Found the expected entry; is it the right proc? */
        visible = (clist->oid == funcid);
        break;
      }
    }
  }

  ReleaseSysCache(proctup);

  return visible;
}


/*
 * OpernameGetOprid
 *    Given a possibly-qualified operator name and exact input datatypes,
 *    look up the operator.  Returns InvalidOid if not found.
 *
 * Pass oprleft = InvalidOid for a prefix op.
 *
 * If the operator name is not schema-qualified, it is sought in the current
 * namespace search path.  If the name is schema-qualified and the given
 * schema does not exist, InvalidOid is returned.
 */
Oid
OpernameGetOprid(List *names, Oid oprleft, Oid oprright)
{
  char     *schemaname;
  char     *opername;
  CatCList   *catlist;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &opername);

  if (schemaname)
  {
    /* search only in exact schema given */
    Oid     namespaceId;

    namespaceId = LookupExplicitNamespace(schemaname, true);
    if (OidIsValid(namespaceId))
    {
      HeapTuple opertup;

      opertup = SearchSysCache4(OPERNAMENSP,
                    CStringGetDatum(opername),
                    ObjectIdGetDatum(oprleft),
                    ObjectIdGetDatum(oprright),
                    ObjectIdGetDatum(namespaceId));
      if (HeapTupleIsValid(opertup))
      {
        Form_pg_operator operclass = (Form_pg_operator) GETSTRUCT(opertup);
        Oid     result = operclass->oid;

        ReleaseSysCache(opertup);
        return result;
      }
    }

    return InvalidOid;
  }

  /* Search syscache by name and argument types */
  catlist = SearchSysCacheList3(OPERNAMENSP,
                  CStringGetDatum(opername),
                  ObjectIdGetDatum(oprleft),
                  ObjectIdGetDatum(oprright));

  if (catlist->n_members == 0)
  {
    /* no hope, fall out early */
    ReleaseSysCacheList(catlist);
    return InvalidOid;
  }

  /*
   * We have to find the list member that is first in the search path, if
   * there's more than one.  This doubly-nested loop looks ugly, but in
   * practice there should usually be few catlist members.
   */
  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);
    int     i;

    if (namespaceId == myTempNamespace)
      continue;     /* do not look in temp namespace */

    for (i = 0; i < catlist->n_members; i++)
    {
      HeapTuple opertup = &catlist->members[i]->tuple;
      Form_pg_operator operform = (Form_pg_operator) GETSTRUCT(opertup);

      if (operform->oprnamespace == namespaceId)
      {
        Oid     result = operform->oid;

        ReleaseSysCacheList(catlist);
        return result;
      }
    }
  }

  ReleaseSysCacheList(catlist);
  return InvalidOid;
}

/*
 * OpernameGetCandidates
 *    Given a possibly-qualified operator name and operator kind,
 *    retrieve a list of the possible matches.
 *
 * If oprkind is '\0', we return all operators matching the given name,
 * regardless of arguments.
 *
 * We search a single namespace if the operator name is qualified, else
 * all namespaces in the search path.  The return list will never contain
 * multiple entries with identical argument lists --- in the multiple-
 * namespace case, we arrange for entries in earlier namespaces to mask
 * identical entries in later namespaces.
 *
 * The returned items always have two args[] entries --- the first will be
 * InvalidOid for a prefix oprkind.  nargs is always 2, too.
 */
FuncCandidateList
OpernameGetCandidates(List *names, char oprkind, bool missing_schema_ok)
{
  FuncCandidateList resultList = NULL;
  char     *resultSpace = NULL;
  int     nextResult = 0;
  char     *schemaname;
  char     *opername;
  Oid     namespaceId;
  CatCList   *catlist;
  int     i;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &opername);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_schema_ok);
    if (missing_schema_ok && !OidIsValid(namespaceId))
      return NULL;
  }
  else
  {
    /* flag to indicate we need namespace search */
    namespaceId = InvalidOid;
    recomputeNamespacePath();
  }

  /* Search syscache by name only */
  catlist = SearchSysCacheList1(OPERNAMENSP, CStringGetDatum(opername));

  /*
   * In typical scenarios, most if not all of the operators found by the
   * catcache search will end up getting returned; and there can be quite a
   * few, for common operator names such as '=' or '+'.  To reduce the time
   * spent in palloc, we allocate the result space as an array large enough
   * to hold all the operators.  The original coding of this routine did a
   * separate palloc for each operator, but profiling revealed that the
   * pallocs used an unreasonably large fraction of parsing time.
   */
#define SPACE_PER_OP MAXALIGN(offsetof(struct _FuncCandidateList, args) + \
                2 * sizeof(Oid))

  if (catlist->n_members > 0)
    resultSpace = palloc(catlist->n_members * SPACE_PER_OP);

  for (i = 0; i < catlist->n_members; i++)
  {
    HeapTuple opertup = &catlist->members[i]->tuple;
    Form_pg_operator operform = (Form_pg_operator) GETSTRUCT(opertup);
    int     pathpos = 0;
    FuncCandidateList newResult;

    /* Ignore operators of wrong kind, if specific kind requested */
    if (oprkind && operform->oprkind != oprkind)
      continue;

    if (OidIsValid(namespaceId))
    {
      /* Consider only opers in specified namespace */
      if (operform->oprnamespace != namespaceId)
        continue;
      /* No need to check args, they must all be different */
    }
    else
    {
      /*
       * Consider only opers that are in the search path and are not in
       * the temp namespace.
       */
      ListCell   *nsp;

      foreach(nsp, activeSearchPath)
      {
        if (operform->oprnamespace == lfirst_oid(nsp) &&
          operform->oprnamespace != myTempNamespace)
          break;
        pathpos++;
      }
      if (nsp == NULL)
        continue;   /* oper is not in search path */

      /*
       * Okay, it's in the search path, but does it have the same
       * arguments as something we already accepted?  If so, keep only
       * the one that appears earlier in the search path.
       *
       * If we have an ordered list from SearchSysCacheList (the normal
       * case), then any conflicting oper must immediately adjoin this
       * one in the list, so we only need to look at the newest result
       * item.  If we have an unordered list, we have to scan the whole
       * result list.
       */
      if (resultList)
      {
        FuncCandidateList prevResult;

        if (catlist->ordered)
        {
          if (operform->oprleft == resultList->args[0] &&
            operform->oprright == resultList->args[1])
            prevResult = resultList;
          else
            prevResult = NULL;
        }
        else
        {
          for (prevResult = resultList;
             prevResult;
             prevResult = prevResult->next)
          {
            if (operform->oprleft == prevResult->args[0] &&
              operform->oprright == prevResult->args[1])
              break;
          }
        }
        if (prevResult)
        {
          /* We have a match with a previous result */
          Assert(pathpos != prevResult->pathpos);
          if (pathpos > prevResult->pathpos)
            continue; /* keep previous result */
          /* replace previous result */
          prevResult->pathpos = pathpos;
          prevResult->oid = operform->oid;
          continue; /* args are same, of course */
        }
      }
    }

    /*
     * Okay to add it to result list
     */
    newResult = (FuncCandidateList) (resultSpace + nextResult);
    nextResult += SPACE_PER_OP;

    newResult->pathpos = pathpos;
    newResult->oid = operform->oid;
    newResult->nominalnargs = 2;
    newResult->nargs = 2;
    newResult->nvargs = 0;
    newResult->ndargs = 0;
    newResult->argnumbers = NULL;
    newResult->args[0] = operform->oprleft;
    newResult->args[1] = operform->oprright;
    newResult->next = resultList;
    resultList = newResult;
  }

  ReleaseSysCacheList(catlist);

  return resultList;
}

/*
 * OperatorIsVisible
 *    Determine whether an operator (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified operator name with exact argument matches".
 */
bool
OperatorIsVisible(Oid oprid)
{
  return OperatorIsVisibleExt(oprid, NULL);
}

/*
 * OperatorIsVisibleExt
 *    As above, but if the operator isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
OperatorIsVisibleExt(Oid oprid, bool *is_missing)
{
  HeapTuple oprtup;
  Form_pg_operator oprform;
  Oid     oprnamespace;
  bool    visible;

  oprtup = SearchSysCache1(OPEROID, ObjectIdGetDatum(oprid));
  if (!HeapTupleIsValid(oprtup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for operator %u", oprid);
  }
  oprform = (Form_pg_operator) GETSTRUCT(oprtup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  oprnamespace = oprform->oprnamespace;
  if (oprnamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, oprnamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another operator of the same name and arguments earlier
     * in the path.  So we must do a slow check to see if this is the same
     * operator that would be found by OpernameGetOprid.
     */
    char     *oprname = NameStr(oprform->oprname);

    visible = (OpernameGetOprid(list_make1(makeString(oprname)),
                  oprform->oprleft, oprform->oprright)
           == oprid);
  }

  ReleaseSysCache(oprtup);

  return visible;
}


/*
 * OpclassnameGetOpcid
 *    Try to resolve an unqualified index opclass name.
 *    Returns OID if opclass found in search path, else InvalidOid.
 *
 * This is essentially the same as TypenameGetTypid, but we have to have
 * an extra argument for the index AM OID.
 */
Oid
OpclassnameGetOpcid(Oid amid, const char *opcname)
{
  Oid     opcid;
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);

    if (namespaceId == myTempNamespace)
      continue;     /* do not look in temp namespace */

    opcid = GetSysCacheOid3(CLAAMNAMENSP, Anum_pg_opclass_oid,
                ObjectIdGetDatum(amid),
                PointerGetDatum(opcname),
                ObjectIdGetDatum(namespaceId));
    if (OidIsValid(opcid))
      return opcid;
  }

  /* Not found in path */
  return InvalidOid;
}

/*
 * OpclassIsVisible
 *    Determine whether an opclass (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified opclass name".
 */
bool
OpclassIsVisible(Oid opcid)
{
  return OpclassIsVisibleExt(opcid, NULL);
}

/*
 * OpclassIsVisibleExt
 *    As above, but if the opclass isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
OpclassIsVisibleExt(Oid opcid, bool *is_missing)
{
  HeapTuple opctup;
  Form_pg_opclass opcform;
  Oid     opcnamespace;
  bool    visible;

  opctup = SearchSysCache1(CLAOID, ObjectIdGetDatum(opcid));
  if (!HeapTupleIsValid(opctup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for opclass %u", opcid);
  }
  opcform = (Form_pg_opclass) GETSTRUCT(opctup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  opcnamespace = opcform->opcnamespace;
  if (opcnamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, opcnamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another opclass of the same name earlier in the path. So
     * we must do a slow check to see if this opclass would be found by
     * OpclassnameGetOpcid.
     */
    char     *opcname = NameStr(opcform->opcname);

    visible = (OpclassnameGetOpcid(opcform->opcmethod, opcname) == opcid);
  }

  ReleaseSysCache(opctup);

  return visible;
}

/*
 * OpfamilynameGetOpfid
 *    Try to resolve an unqualified index opfamily name.
 *    Returns OID if opfamily found in search path, else InvalidOid.
 *
 * This is essentially the same as TypenameGetTypid, but we have to have
 * an extra argument for the index AM OID.
 */
Oid
OpfamilynameGetOpfid(Oid amid, const char *opfname)
{
  Oid     opfid;
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);

    if (namespaceId == myTempNamespace)
      continue;     /* do not look in temp namespace */

    opfid = GetSysCacheOid3(OPFAMILYAMNAMENSP, Anum_pg_opfamily_oid,
                ObjectIdGetDatum(amid),
                PointerGetDatum(opfname),
                ObjectIdGetDatum(namespaceId));
    if (OidIsValid(opfid))
      return opfid;
  }

  /* Not found in path */
  return InvalidOid;
}

/*
 * OpfamilyIsVisible
 *    Determine whether an opfamily (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified opfamily name".
 */
bool
OpfamilyIsVisible(Oid opfid)
{
  return OpfamilyIsVisibleExt(opfid, NULL);
}

/*
 * OpfamilyIsVisibleExt
 *    As above, but if the opfamily isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
OpfamilyIsVisibleExt(Oid opfid, bool *is_missing)
{
  HeapTuple opftup;
  Form_pg_opfamily opfform;
  Oid     opfnamespace;
  bool    visible;

  opftup = SearchSysCache1(OPFAMILYOID, ObjectIdGetDatum(opfid));
  if (!HeapTupleIsValid(opftup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for opfamily %u", opfid);
  }
  opfform = (Form_pg_opfamily) GETSTRUCT(opftup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  opfnamespace = opfform->opfnamespace;
  if (opfnamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, opfnamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another opfamily of the same name earlier in the path. So
     * we must do a slow check to see if this opfamily would be found by
     * OpfamilynameGetOpfid.
     */
    char     *opfname = NameStr(opfform->opfname);

    visible = (OpfamilynameGetOpfid(opfform->opfmethod, opfname) == opfid);
  }

  ReleaseSysCache(opftup);

  return visible;
}

/*
 * lookup_collation
 *    If there's a collation of the given name/namespace, and it works
 *    with the given encoding, return its OID.  Else return InvalidOid.
 */
static Oid
lookup_collation(const char *collname, Oid collnamespace, int32 encoding)
{
  Oid     collid;
  HeapTuple colltup;
  Form_pg_collation collform;

  /* Check for encoding-specific entry (exact match) */
  collid = GetSysCacheOid3(COLLNAMEENCNSP, Anum_pg_collation_oid,
               PointerGetDatum(collname),
               Int32GetDatum(encoding),
               ObjectIdGetDatum(collnamespace));
  if (OidIsValid(collid))
    return collid;

  /*
   * Check for any-encoding entry.  This takes a bit more work: while libc
   * collations with collencoding = -1 do work with all encodings, ICU
   * collations only work with certain encodings, so we have to check that
   * aspect before deciding it's a match.
   */
  colltup = SearchSysCache3(COLLNAMEENCNSP,
                PointerGetDatum(collname),
                Int32GetDatum(-1),
                ObjectIdGetDatum(collnamespace));
  if (!HeapTupleIsValid(colltup))
    return InvalidOid;
  collform = (Form_pg_collation) GETSTRUCT(colltup);
  if (collform->collprovider == COLLPROVIDER_ICU)
  {
    if (is_encoding_supported_by_icu(encoding))
      collid = collform->oid;
    else
      collid = InvalidOid;
  }
  else
  {
    collid = collform->oid;
  }
  ReleaseSysCache(colltup);
  return collid;
}

/*
 * CollationGetCollid
 *    Try to resolve an unqualified collation name.
 *    Returns OID if collation found in search path, else InvalidOid.
 *
 * Note that this will only find collations that work with the current
 * database's encoding.
 */
Oid
CollationGetCollid(const char *collname)
{
  int32   dbencoding = GetDatabaseEncoding();
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);
    Oid     collid;

    if (namespaceId == myTempNamespace)
      continue;     /* do not look in temp namespace */

    collid = lookup_collation(collname, namespaceId, dbencoding);
    if (OidIsValid(collid))
      return collid;
  }

  /* Not found in path */
  return InvalidOid;
}

/*
 * CollationIsVisible
 *    Determine whether a collation (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified collation name".
 *
 * Note that only collations that work with the current database's encoding
 * will be considered visible.
 */
bool
CollationIsVisible(Oid collid)
{
  return CollationIsVisibleExt(collid, NULL);
}

/*
 * CollationIsVisibleExt
 *    As above, but if the collation isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
CollationIsVisibleExt(Oid collid, bool *is_missing)
{
  HeapTuple colltup;
  Form_pg_collation collform;
  Oid     collnamespace;
  bool    visible;

  colltup = SearchSysCache1(COLLOID, ObjectIdGetDatum(collid));
  if (!HeapTupleIsValid(colltup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for collation %u", collid);
  }
  collform = (Form_pg_collation) GETSTRUCT(colltup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  collnamespace = collform->collnamespace;
  if (collnamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, collnamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another collation of the same name earlier in the path,
     * or it might not work with the current DB encoding.  So we must do a
     * slow check to see if this collation would be found by
     * CollationGetCollid.
     */
    char     *collname = NameStr(collform->collname);

    visible = (CollationGetCollid(collname) == collid);
  }

  ReleaseSysCache(colltup);

  return visible;
}


/*
 * ConversionGetConid
 *    Try to resolve an unqualified conversion name.
 *    Returns OID if conversion found in search path, else InvalidOid.
 *
 * This is essentially the same as RelnameGetRelid.
 */
Oid
ConversionGetConid(const char *conname)
{
  Oid     conid;
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);

    if (namespaceId == myTempNamespace)
      continue;     /* do not look in temp namespace */

    conid = GetSysCacheOid2(CONNAMENSP, Anum_pg_conversion_oid,
                PointerGetDatum(conname),
                ObjectIdGetDatum(namespaceId));
    if (OidIsValid(conid))
      return conid;
  }

  /* Not found in path */
  return InvalidOid;
}

/*
 * ConversionIsVisible
 *    Determine whether a conversion (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified conversion name".
 */
bool
ConversionIsVisible(Oid conid)
{
  return ConversionIsVisibleExt(conid, NULL);
}

/*
 * ConversionIsVisibleExt
 *    As above, but if the conversion isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
ConversionIsVisibleExt(Oid conid, bool *is_missing)
{
  HeapTuple contup;
  Form_pg_conversion conform;
  Oid     connamespace;
  bool    visible;

  contup = SearchSysCache1(CONVOID, ObjectIdGetDatum(conid));
  if (!HeapTupleIsValid(contup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for conversion %u", conid);
  }
  conform = (Form_pg_conversion) GETSTRUCT(contup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  connamespace = conform->connamespace;
  if (connamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, connamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another conversion of the same name earlier in the path.
     * So we must do a slow check to see if this conversion would be found
     * by ConversionGetConid.
     */
    char     *conname = NameStr(conform->conname);

    visible = (ConversionGetConid(conname) == conid);
  }

  ReleaseSysCache(contup);

  return visible;
}

/*
 * get_statistics_object_oid - find a statistics object by possibly qualified name
 *
 * If not found, returns InvalidOid if missing_ok, else throws error
 */
Oid
get_statistics_object_oid(List *names, bool missing_ok)
{
  char     *schemaname;
  char     *stats_name;
  Oid     namespaceId;
  Oid     stats_oid = InvalidOid;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &stats_name);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (missing_ok && !OidIsValid(namespaceId))
      stats_oid = InvalidOid;
    else
      stats_oid = GetSysCacheOid2(STATEXTNAMENSP, Anum_pg_statistic_ext_oid,
                    PointerGetDatum(stats_name),
                    ObjectIdGetDatum(namespaceId));
  }
  else
  {
    /* search for it in search path */
    recomputeNamespacePath();

    foreach(l, activeSearchPath)
    {
      namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */
      stats_oid = GetSysCacheOid2(STATEXTNAMENSP, Anum_pg_statistic_ext_oid,
                    PointerGetDatum(stats_name),
                    ObjectIdGetDatum(namespaceId));
      if (OidIsValid(stats_oid))
        break;
    }
  }

  if (!OidIsValid(stats_oid) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("statistics object \"%s\" does not exist",
            NameListToString(names))));

  return stats_oid;
}

/*
 * StatisticsObjIsVisible
 *    Determine whether a statistics object (identified by OID) is visible in
 *    the current search path.  Visible means "would be found by searching
 *    for the unqualified statistics object name".
 */
bool
StatisticsObjIsVisible(Oid stxid)
{
  return StatisticsObjIsVisibleExt(stxid, NULL);
}

/*
 * StatisticsObjIsVisibleExt
 *    As above, but if the statistics object isn't found and is_missing is
 *    not NULL, then set *is_missing = true and return false instead of
 *    throwing an error.  (Caller must initialize *is_missing = false.)
 */
static bool
StatisticsObjIsVisibleExt(Oid stxid, bool *is_missing)
{
  HeapTuple stxtup;
  Form_pg_statistic_ext stxform;
  Oid     stxnamespace;
  bool    visible;

  stxtup = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
  if (!HeapTupleIsValid(stxtup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for statistics object %u", stxid);
  }
  stxform = (Form_pg_statistic_ext) GETSTRUCT(stxtup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  stxnamespace = stxform->stxnamespace;
  if (stxnamespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, stxnamespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another statistics object of the same name earlier in the
     * path. So we must do a slow check for conflicting objects.
     */
    char     *stxname = NameStr(stxform->stxname);
    ListCell   *l;

    visible = false;
    foreach(l, activeSearchPath)
    {
      Oid     namespaceId = lfirst_oid(l);

      if (namespaceId == stxnamespace)
      {
        /* Found it first in path */
        visible = true;
        break;
      }
      if (SearchSysCacheExists2(STATEXTNAMENSP,
                    PointerGetDatum(stxname),
                    ObjectIdGetDatum(namespaceId)))
      {
        /* Found something else first in path */
        break;
      }
    }
  }

  ReleaseSysCache(stxtup);

  return visible;
}

/*
 * get_ts_parser_oid - find a TS parser by possibly qualified name
 *
 * If not found, returns InvalidOid if missing_ok, else throws error
 */
Oid
get_ts_parser_oid(List *names, bool missing_ok)
{
  char     *schemaname;
  char     *parser_name;
  Oid     namespaceId;
  Oid     prsoid = InvalidOid;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &parser_name);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (missing_ok && !OidIsValid(namespaceId))
      prsoid = InvalidOid;
    else
      prsoid = GetSysCacheOid2(TSPARSERNAMENSP, Anum_pg_ts_parser_oid,
                   PointerGetDatum(parser_name),
                   ObjectIdGetDatum(namespaceId));
  }
  else
  {
    /* search for it in search path */
    recomputeNamespacePath();

    foreach(l, activeSearchPath)
    {
      namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      prsoid = GetSysCacheOid2(TSPARSERNAMENSP, Anum_pg_ts_parser_oid,
                   PointerGetDatum(parser_name),
                   ObjectIdGetDatum(namespaceId));
      if (OidIsValid(prsoid))
        break;
    }
  }

  if (!OidIsValid(prsoid) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("text search parser \"%s\" does not exist",
            NameListToString(names))));

  return prsoid;
}

/*
 * TSParserIsVisible
 *    Determine whether a parser (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified parser name".
 */
bool
TSParserIsVisible(Oid prsId)
{
  return TSParserIsVisibleExt(prsId, NULL);
}

/*
 * TSParserIsVisibleExt
 *    As above, but if the parser isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
TSParserIsVisibleExt(Oid prsId, bool *is_missing)
{
  HeapTuple tup;
  Form_pg_ts_parser form;
  Oid     namespace;
  bool    visible;

  tup = SearchSysCache1(TSPARSEROID, ObjectIdGetDatum(prsId));
  if (!HeapTupleIsValid(tup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for text search parser %u", prsId);
  }
  form = (Form_pg_ts_parser) GETSTRUCT(tup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  namespace = form->prsnamespace;
  if (namespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, namespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another parser of the same name earlier in the path. So
     * we must do a slow check for conflicting parsers.
     */
    char     *name = NameStr(form->prsname);
    ListCell   *l;

    visible = false;
    foreach(l, activeSearchPath)
    {
      Oid     namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      if (namespaceId == namespace)
      {
        /* Found it first in path */
        visible = true;
        break;
      }
      if (SearchSysCacheExists2(TSPARSERNAMENSP,
                    PointerGetDatum(name),
                    ObjectIdGetDatum(namespaceId)))
      {
        /* Found something else first in path */
        break;
      }
    }
  }

  ReleaseSysCache(tup);

  return visible;
}

/*
 * get_ts_dict_oid - find a TS dictionary by possibly qualified name
 *
 * If not found, returns InvalidOid if missing_ok, else throws error
 */
Oid
get_ts_dict_oid(List *names, bool missing_ok)
{
  char     *schemaname;
  char     *dict_name;
  Oid     namespaceId;
  Oid     dictoid = InvalidOid;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &dict_name);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (missing_ok && !OidIsValid(namespaceId))
      dictoid = InvalidOid;
    else
      dictoid = GetSysCacheOid2(TSDICTNAMENSP, Anum_pg_ts_dict_oid,
                    PointerGetDatum(dict_name),
                    ObjectIdGetDatum(namespaceId));
  }
  else
  {
    /* search for it in search path */
    recomputeNamespacePath();

    foreach(l, activeSearchPath)
    {
      namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      dictoid = GetSysCacheOid2(TSDICTNAMENSP, Anum_pg_ts_dict_oid,
                    PointerGetDatum(dict_name),
                    ObjectIdGetDatum(namespaceId));
      if (OidIsValid(dictoid))
        break;
    }
  }

  if (!OidIsValid(dictoid) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("text search dictionary \"%s\" does not exist",
            NameListToString(names))));

  return dictoid;
}

/*
 * TSDictionaryIsVisible
 *    Determine whether a dictionary (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified dictionary name".
 */
bool
TSDictionaryIsVisible(Oid dictId)
{
  return TSDictionaryIsVisibleExt(dictId, NULL);
}

/*
 * TSDictionaryIsVisibleExt
 *    As above, but if the dictionary isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
TSDictionaryIsVisibleExt(Oid dictId, bool *is_missing)
{
  HeapTuple tup;
  Form_pg_ts_dict form;
  Oid     namespace;
  bool    visible;

  tup = SearchSysCache1(TSDICTOID, ObjectIdGetDatum(dictId));
  if (!HeapTupleIsValid(tup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for text search dictionary %u",
       dictId);
  }
  form = (Form_pg_ts_dict) GETSTRUCT(tup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  namespace = form->dictnamespace;
  if (namespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, namespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another dictionary of the same name earlier in the path.
     * So we must do a slow check for conflicting dictionaries.
     */
    char     *name = NameStr(form->dictname);
    ListCell   *l;

    visible = false;
    foreach(l, activeSearchPath)
    {
      Oid     namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      if (namespaceId == namespace)
      {
        /* Found it first in path */
        visible = true;
        break;
      }
      if (SearchSysCacheExists2(TSDICTNAMENSP,
                    PointerGetDatum(name),
                    ObjectIdGetDatum(namespaceId)))
      {
        /* Found something else first in path */
        break;
      }
    }
  }

  ReleaseSysCache(tup);

  return visible;
}

/*
 * get_ts_template_oid - find a TS template by possibly qualified name
 *
 * If not found, returns InvalidOid if missing_ok, else throws error
 */
Oid
get_ts_template_oid(List *names, bool missing_ok)
{
  char     *schemaname;
  char     *template_name;
  Oid     namespaceId;
  Oid     tmploid = InvalidOid;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &template_name);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (missing_ok && !OidIsValid(namespaceId))
      tmploid = InvalidOid;
    else
      tmploid = GetSysCacheOid2(TSTEMPLATENAMENSP, Anum_pg_ts_template_oid,
                    PointerGetDatum(template_name),
                    ObjectIdGetDatum(namespaceId));
  }
  else
  {
    /* search for it in search path */
    recomputeNamespacePath();

    foreach(l, activeSearchPath)
    {
      namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      tmploid = GetSysCacheOid2(TSTEMPLATENAMENSP, Anum_pg_ts_template_oid,
                    PointerGetDatum(template_name),
                    ObjectIdGetDatum(namespaceId));
      if (OidIsValid(tmploid))
        break;
    }
  }

  if (!OidIsValid(tmploid) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("text search template \"%s\" does not exist",
            NameListToString(names))));

  return tmploid;
}

/*
 * TSTemplateIsVisible
 *    Determine whether a template (identified by OID) is visible in the
 *    current search path.  Visible means "would be found by searching
 *    for the unqualified template name".
 */
bool
TSTemplateIsVisible(Oid tmplId)
{
  return TSTemplateIsVisibleExt(tmplId, NULL);
}

/*
 * TSTemplateIsVisibleExt
 *    As above, but if the template isn't found and is_missing is not NULL,
 *    then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
TSTemplateIsVisibleExt(Oid tmplId, bool *is_missing)
{
  HeapTuple tup;
  Form_pg_ts_template form;
  Oid     namespace;
  bool    visible;

  tup = SearchSysCache1(TSTEMPLATEOID, ObjectIdGetDatum(tmplId));
  if (!HeapTupleIsValid(tup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for text search template %u", tmplId);
  }
  form = (Form_pg_ts_template) GETSTRUCT(tup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  namespace = form->tmplnamespace;
  if (namespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, namespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another template of the same name earlier in the path. So
     * we must do a slow check for conflicting templates.
     */
    char     *name = NameStr(form->tmplname);
    ListCell   *l;

    visible = false;
    foreach(l, activeSearchPath)
    {
      Oid     namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      if (namespaceId == namespace)
      {
        /* Found it first in path */
        visible = true;
        break;
      }
      if (SearchSysCacheExists2(TSTEMPLATENAMENSP,
                    PointerGetDatum(name),
                    ObjectIdGetDatum(namespaceId)))
      {
        /* Found something else first in path */
        break;
      }
    }
  }

  ReleaseSysCache(tup);

  return visible;
}

/*
 * get_ts_config_oid - find a TS config by possibly qualified name
 *
 * If not found, returns InvalidOid if missing_ok, else throws error
 */
Oid
get_ts_config_oid(List *names, bool missing_ok)
{
  char     *schemaname;
  char     *config_name;
  Oid     namespaceId;
  Oid     cfgoid = InvalidOid;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, &config_name);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (missing_ok && !OidIsValid(namespaceId))
      cfgoid = InvalidOid;
    else
      cfgoid = GetSysCacheOid2(TSCONFIGNAMENSP, Anum_pg_ts_config_oid,
                   PointerGetDatum(config_name),
                   ObjectIdGetDatum(namespaceId));
  }
  else
  {
    /* search for it in search path */
    recomputeNamespacePath();

    foreach(l, activeSearchPath)
    {
      namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      cfgoid = GetSysCacheOid2(TSCONFIGNAMENSP, Anum_pg_ts_config_oid,
                   PointerGetDatum(config_name),
                   ObjectIdGetDatum(namespaceId));
      if (OidIsValid(cfgoid))
        break;
    }
  }

  if (!OidIsValid(cfgoid) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("text search configuration \"%s\" does not exist",
            NameListToString(names))));

  return cfgoid;
}

/*
 * TSConfigIsVisible
 *    Determine whether a text search configuration (identified by OID)
 *    is visible in the current search path.  Visible means "would be found
 *    by searching for the unqualified text search configuration name".
 */
bool
TSConfigIsVisible(Oid cfgid)
{
  return TSConfigIsVisibleExt(cfgid, NULL);
}

/*
 * TSConfigIsVisibleExt
 *    As above, but if the configuration isn't found and is_missing is not
 *    NULL, then set *is_missing = true and return false instead of throwing
 *    an error.  (Caller must initialize *is_missing = false.)
 */
static bool
TSConfigIsVisibleExt(Oid cfgid, bool *is_missing)
{
  HeapTuple tup;
  Form_pg_ts_config form;
  Oid     namespace;
  bool    visible;

  tup = SearchSysCache1(TSCONFIGOID, ObjectIdGetDatum(cfgid));
  if (!HeapTupleIsValid(tup))
  {
    if (is_missing != NULL)
    {
      *is_missing = true;
      return false;
    }
    elog(ERROR, "cache lookup failed for text search configuration %u",
       cfgid);
  }
  form = (Form_pg_ts_config) GETSTRUCT(tup);

  recomputeNamespacePath();

  /*
   * Quick check: if it ain't in the path at all, it ain't visible. Items in
   * the system namespace are surely in the path and so we needn't even do
   * list_member_oid() for them.
   */
  namespace = form->cfgnamespace;
  if (namespace != PG_CATALOG_NAMESPACE &&
    !list_member_oid(activeSearchPath, namespace))
    visible = false;
  else
  {
    /*
     * If it is in the path, it might still not be visible; it could be
     * hidden by another configuration of the same name earlier in the
     * path. So we must do a slow check for conflicting configurations.
     */
    char     *name = NameStr(form->cfgname);
    ListCell   *l;

    visible = false;
    foreach(l, activeSearchPath)
    {
      Oid     namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      if (namespaceId == namespace)
      {
        /* Found it first in path */
        visible = true;
        break;
      }
      if (SearchSysCacheExists2(TSCONFIGNAMENSP,
                    PointerGetDatum(name),
                    ObjectIdGetDatum(namespaceId)))
      {
        /* Found something else first in path */
        break;
      }
    }
  }

  ReleaseSysCache(tup);

  return visible;
}


/*
 * DeconstructQualifiedName
 *    Given a possibly-qualified name expressed as a list of String nodes,
 *    extract the schema name and object name.
 *
 * *nspname_p is set to NULL if there is no explicit schema name.
 */
void
DeconstructQualifiedName(const List *names,
             char **nspname_p,
             char **objname_p)
{
  char     *catalogname;
  char     *schemaname = NULL;
  char     *objname = NULL;

  switch (list_length(names))
  {
    case 1:
      objname = strVal(linitial(names));
      break;
    case 2:
      schemaname = strVal(linitial(names));
      objname = strVal(lsecond(names));
      break;
    case 3:
      catalogname = strVal(linitial(names));
      schemaname = strVal(lsecond(names));
      objname = strVal(lthird(names));

      /*
       * We check the catalog name and then ignore it.
       */
      if (strcmp(catalogname, get_database_name(MyDatabaseId)) != 0)
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("cross-database references are not implemented: %s",
                NameListToString(names))));
      break;
    default:
      ereport(ERROR,
          (errcode(ERRCODE_SYNTAX_ERROR),
           errmsg("improper qualified name (too many dotted names): %s",
              NameListToString(names))));
      break;
  }

  *nspname_p = schemaname;
  *objname_p = objname;
}

/*
 * LookupNamespaceNoError
 *    Look up a schema name.
 *
 * Returns the namespace OID, or InvalidOid if not found.
 *
 * Note this does NOT perform any permissions check --- callers are
 * responsible for being sure that an appropriate check is made.
 * In the majority of cases LookupExplicitNamespace is preferable.
 */
Oid
LookupNamespaceNoError(const char *nspname)
{
  /* check for pg_temp alias */
  if (strcmp(nspname, "pg_temp") == 0)
  {
    if (OidIsValid(myTempNamespace))
    {
      InvokeNamespaceSearchHook(myTempNamespace, true);
      return myTempNamespace;
    }

    /*
     * Since this is used only for looking up existing objects, there is
     * no point in trying to initialize the temp namespace here; and doing
     * so might create problems for some callers. Just report "not found".
     */
    return InvalidOid;
  }

  return get_namespace_oid(nspname, true);
}

/*
 * LookupExplicitNamespace
 *    Process an explicitly-specified schema name: look up the schema
 *    and verify we have USAGE (lookup) rights in it.
 *
 * Returns the namespace OID
 */
Oid
LookupExplicitNamespace(const char *nspname, bool missing_ok)
{
  Oid     namespaceId;
  AclResult aclresult;

  /* check for pg_temp alias */
  if (strcmp(nspname, "pg_temp") == 0)
  {
    if (OidIsValid(myTempNamespace))
      return myTempNamespace;

    /*
     * Since this is used only for looking up existing objects, there is
     * no point in trying to initialize the temp namespace here; and doing
     * so might create problems for some callers --- just fall through.
     */
  }

  namespaceId = get_namespace_oid(nspname, missing_ok);
  if (missing_ok && !OidIsValid(namespaceId))
    return InvalidOid;

  aclresult = object_aclcheck(NamespaceRelationId, namespaceId, GetUserId(), ACL_USAGE);
  if (aclresult != ACLCHECK_OK)
    aclcheck_error(aclresult, OBJECT_SCHEMA,
             nspname);
  /* Schema search hook for this lookup */
  InvokeNamespaceSearchHook(namespaceId, true);

  return namespaceId;
}

/*
 * LookupCreationNamespace
 *    Look up the schema and verify we have CREATE rights on it.
 *
 * This is just like LookupExplicitNamespace except for the different
 * permission check, and that we are willing to create pg_temp if needed.
 *
 * Note: calling this may result in a CommandCounterIncrement operation,
 * if we have to create or clean out the temp namespace.
 */
Oid
LookupCreationNamespace(const char *nspname)
{
  Oid     namespaceId;
  AclResult aclresult;

  /* check for pg_temp alias */
  if (strcmp(nspname, "pg_temp") == 0)
  {
    /* Initialize temp namespace */
    AccessTempTableNamespace(false);
    return myTempNamespace;
  }

  namespaceId = get_namespace_oid(nspname, false);

  aclresult = object_aclcheck(NamespaceRelationId, namespaceId, GetUserId(), ACL_CREATE);
  if (aclresult != ACLCHECK_OK)
    aclcheck_error(aclresult, OBJECT_SCHEMA,
             nspname);

  return namespaceId;
}

/*
 * Common checks on switching namespaces.
 *
 * We complain if either the old or new namespaces is a temporary schema
 * (or temporary toast schema), or if either the old or new namespaces is the
 * TOAST schema.
 */
void
CheckSetNamespace(Oid oldNspOid, Oid nspOid)
{
  /* disallow renaming into or out of temp schemas */
  if (isAnyTempNamespace(nspOid) || isAnyTempNamespace(oldNspOid))
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("cannot move objects into or out of temporary schemas")));

  /* same for TOAST schema */
  if (nspOid == PG_TOAST_NAMESPACE || oldNspOid == PG_TOAST_NAMESPACE)
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("cannot move objects into or out of TOAST schema")));
}

/*
 * QualifiedNameGetCreationNamespace
 *    Given a possibly-qualified name for an object (in List-of-Strings
 *    format), determine what namespace the object should be created in.
 *    Also extract and return the object name (last component of list).
 *
 * Note: this does not apply any permissions check.  Callers must check
 * for CREATE rights on the selected namespace when appropriate.
 *
 * Note: calling this may result in a CommandCounterIncrement operation,
 * if we have to create or clean out the temp namespace.
 */
Oid
QualifiedNameGetCreationNamespace(const List *names, char **objname_p)
{
  char     *schemaname;
  Oid     namespaceId;

  /* deconstruct the name list */
  DeconstructQualifiedName(names, &schemaname, objname_p);

  if (schemaname)
  {
    /* check for pg_temp alias */
    if (strcmp(schemaname, "pg_temp") == 0)
    {
      /* Initialize temp namespace */
      AccessTempTableNamespace(false);
      return myTempNamespace;
    }
    /* use exact schema given */
    namespaceId = get_namespace_oid(schemaname, false);
    /* we do not check for USAGE rights here! */
  }
  else
  {
    /* use the default creation namespace */
    recomputeNamespacePath();
    if (activeTempCreationPending)
    {
      /* Need to initialize temp namespace */
      AccessTempTableNamespace(true);
      return myTempNamespace;
    }
    namespaceId = activeCreationNamespace;
    if (!OidIsValid(namespaceId))
      ereport(ERROR,
          (errcode(ERRCODE_UNDEFINED_SCHEMA),
           errmsg("no schema has been selected to create in")));
  }

  return namespaceId;
}

/*
 * get_namespace_oid - given a namespace name, look up the OID
 *
 * If missing_ok is false, throw an error if namespace name not found.  If
 * true, just return InvalidOid.
 */
Oid
get_namespace_oid(const char *nspname, bool missing_ok)
{
  Oid     oid;

  oid = GetSysCacheOid1(NAMESPACENAME, Anum_pg_namespace_oid,
              CStringGetDatum(nspname));
  if (!OidIsValid(oid) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_SCHEMA),
         errmsg("schema \"%s\" does not exist", nspname)));

  return oid;
}

/*
 * makeRangeVarFromNameList
 *    Utility routine to convert a qualified-name list into RangeVar form.
 */
RangeVar *
makeRangeVarFromNameList(const List *names)
{
  RangeVar   *rel = makeRangeVar(NULL, NULL, -1);

  switch (list_length(names))
  {
    case 1:
      rel->relname = strVal(linitial(names));
      break;
    case 2:
      rel->schemaname = strVal(linitial(names));
      rel->relname = strVal(lsecond(names));
      break;
    case 3:
      rel->catalogname = strVal(linitial(names));
      rel->schemaname = strVal(lsecond(names));
      rel->relname = strVal(lthird(names));
      break;
    default:
      ereport(ERROR,
          (errcode(ERRCODE_SYNTAX_ERROR),
           errmsg("improper relation name (too many dotted names): %s",
              NameListToString(names))));
      break;
  }

  return rel;
}

/*
 * NameListToString
 *    Utility routine to convert a qualified-name list into a string.
 *
 * This is used primarily to form error messages, and so we do not quote
 * the list elements, for the sake of legibility.
 *
 * In most scenarios the list elements should always be String values,
 * but we also allow A_Star for the convenience of ColumnRef processing.
 */
char *
NameListToString(const List *names)
{
  StringInfoData string;
  ListCell   *l;

  initStringInfo(&string);

  foreach(l, names)
  {
    Node     *name = (Node *) lfirst(l);

    if (l != list_head(names))
      appendStringInfoChar(&string, '.');

    if (IsA(name, String))
      appendStringInfoString(&string, strVal(name));
    else if (IsA(name, A_Star))
      appendStringInfoChar(&string, '*');
    else
      elog(ERROR, "unexpected node type in name list: %d",
         (int) nodeTag(name));
  }

  return string.data;
}

/*
 * NameListToQuotedString
 *    Utility routine to convert a qualified-name list into a string.
 *
 * Same as above except that names will be double-quoted where necessary,
 * so the string could be re-parsed (eg, by textToQualifiedNameList).
 */
char *
NameListToQuotedString(const List *names)
{
  StringInfoData string;
  ListCell   *l;

  initStringInfo(&string);

  foreach(l, names)
  {
    if (l != list_head(names))
      appendStringInfoChar(&string, '.');
    appendStringInfoString(&string, quote_identifier(strVal(lfirst(l))));
  }

  return string.data;
}

/*
 * isTempNamespace - is the given namespace my temporary-table namespace?
 */
bool
isTempNamespace(Oid namespaceId)
{
  if (OidIsValid(myTempNamespace) && myTempNamespace == namespaceId)
    return true;
  return false;
}

/*
 * isTempToastNamespace - is the given namespace my temporary-toast-table
 *    namespace?
 */
bool
isTempToastNamespace(Oid namespaceId)
{
  if (OidIsValid(myTempToastNamespace) && myTempToastNamespace == namespaceId)
    return true;
  return false;
}

/*
 * isTempOrTempToastNamespace - is the given namespace my temporary-table
 *    namespace or my temporary-toast-table namespace?
 */
bool
isTempOrTempToastNamespace(Oid namespaceId)
{
  if (OidIsValid(myTempNamespace) &&
    (myTempNamespace == namespaceId || myTempToastNamespace == namespaceId))
    return true;
  return false;
}

/*
 * isAnyTempNamespace - is the given namespace a temporary-table namespace
 * (either my own, or another backend's)?  Temporary-toast-table namespaces
 * are included, too.
 */
bool
isAnyTempNamespace(Oid namespaceId)
{
  bool    result;
  char     *nspname;

  /* True if the namespace name starts with "pg_temp_" or "pg_toast_temp_" */
  nspname = get_namespace_name(namespaceId);
  if (!nspname)
    return false;     /* no such namespace? */
  result = (strncmp(nspname, "pg_temp_", 8) == 0) ||
    (strncmp(nspname, "pg_toast_temp_", 14) == 0);
  pfree(nspname);
  return result;
}

/*
 * isOtherTempNamespace - is the given namespace some other backend's
 * temporary-table namespace (including temporary-toast-table namespaces)?
 *
 * Note: for most purposes in the C code, this function is obsolete.  Use
 * RELATION_IS_OTHER_TEMP() instead to detect non-local temp relations.
 */
bool
isOtherTempNamespace(Oid namespaceId)
{
  /* If it's my own temp namespace, say "false" */
  if (isTempOrTempToastNamespace(namespaceId))
    return false;
  /* Else, if it's any temp namespace, say "true" */
  return isAnyTempNamespace(namespaceId);
}

/*
 * checkTempNamespaceStatus - is the given namespace owned and actively used
 * by a backend?
 *
 * Note: this can be used while scanning relations in pg_class to detect
 * orphaned temporary tables or namespaces with a backend connected to a
 * given database.  The result may be out of date quickly, so the caller
 * must be careful how to handle this information.
 */
TempNamespaceStatus
checkTempNamespaceStatus(Oid namespaceId)
{
  PGPROC     *proc;
  ProcNumber  procNumber;

  Assert(OidIsValid(MyDatabaseId));

  procNumber = GetTempNamespaceProcNumber(namespaceId);

  /* No such namespace, or its name shows it's not temp? */
  if (procNumber == INVALID_PROC_NUMBER)
    return TEMP_NAMESPACE_NOT_TEMP;

  /* Is the backend alive? */
  proc = ProcNumberGetProc(procNumber);
  if (proc == NULL)
    return TEMP_NAMESPACE_IDLE;

  /* Is the backend connected to the same database we are looking at? */
  if (proc->databaseId != MyDatabaseId)
    return TEMP_NAMESPACE_IDLE;

  /* Does the backend own the temporary namespace? */
  if (proc->tempNamespaceId != namespaceId)
    return TEMP_NAMESPACE_IDLE;

  /* Yup, so namespace is busy */
  return TEMP_NAMESPACE_IN_USE;
}

/*
 * GetTempNamespaceProcNumber - if the given namespace is a temporary-table
 * namespace (either my own, or another backend's), return the proc number
 * that owns it.  Temporary-toast-table namespaces are included, too.
 * If it isn't a temp namespace, return INVALID_PROC_NUMBER.
 */
ProcNumber
GetTempNamespaceProcNumber(Oid namespaceId)
{
  int     result;
  char     *nspname;

  /* See if the namespace name starts with "pg_temp_" or "pg_toast_temp_" */
  nspname = get_namespace_name(namespaceId);
  if (!nspname)
    return INVALID_PROC_NUMBER; /* no such namespace? */
  if (strncmp(nspname, "pg_temp_", 8) == 0)
    result = atoi(nspname + 8);
  else if (strncmp(nspname, "pg_toast_temp_", 14) == 0)
    result = atoi(nspname + 14);
  else
    result = INVALID_PROC_NUMBER;
  pfree(nspname);
  return result;
}

/*
 * GetTempToastNamespace - get the OID of my temporary-toast-table namespace,
 * which must already be assigned.  (This is only used when creating a toast
 * table for a temp table, so we must have already done InitTempTableNamespace)
 */
Oid
GetTempToastNamespace(void)
{
  Assert(OidIsValid(myTempToastNamespace));
  return myTempToastNamespace;
}


/*
 * GetTempNamespaceState - fetch status of session's temporary namespace
 *
 * This is used for conveying state to a parallel worker, and is not meant
 * for general-purpose access.
 */
void
GetTempNamespaceState(Oid *tempNamespaceId, Oid *tempToastNamespaceId)
{
  /* Return namespace OIDs, or 0 if session has not created temp namespace */
  *tempNamespaceId = myTempNamespace;
  *tempToastNamespaceId = myTempToastNamespace;
}

/*
 * SetTempNamespaceState - set status of session's temporary namespace
 *
 * This is used for conveying state to a parallel worker, and is not meant for
 * general-purpose access.  By transferring these namespace OIDs to workers,
 * we ensure they will have the same notion of the search path as their leader
 * does.
 */
void
SetTempNamespaceState(Oid tempNamespaceId, Oid tempToastNamespaceId)
{
  /* Worker should not have created its own namespaces ... */
  Assert(myTempNamespace == InvalidOid);
  Assert(myTempToastNamespace == InvalidOid);
  Assert(myTempNamespaceSubID == InvalidSubTransactionId);

  /* Assign same namespace OIDs that leader has */
  myTempNamespace = tempNamespaceId;
  myTempToastNamespace = tempToastNamespaceId;

  /*
   * It's fine to leave myTempNamespaceSubID == InvalidSubTransactionId.
   * Even if the namespace is new so far as the leader is concerned, it's
   * not new to the worker, and we certainly wouldn't want the worker trying
   * to destroy it.
   */

  baseSearchPathValid = false;  /* may need to rebuild list */
  searchPathCacheValid = false;
}


/*
 * GetSearchPathMatcher - fetch current search path definition.
 *
 * The result structure is allocated in the specified memory context
 * (which might or might not be equal to CurrentMemoryContext); but any
 * junk created by revalidation calculations will be in CurrentMemoryContext.
 */
SearchPathMatcher *
GetSearchPathMatcher(MemoryContext context)
{
  SearchPathMatcher *result;
  List     *schemas;
  MemoryContext oldcxt;

  recomputeNamespacePath();

  oldcxt = MemoryContextSwitchTo(context);

  result = (SearchPathMatcher *) palloc0(sizeof(SearchPathMatcher));
  schemas = list_copy(activeSearchPath);
  while (schemas && linitial_oid(schemas) != activeCreationNamespace)
  {
    if (linitial_oid(schemas) == myTempNamespace)
      result->addTemp = true;
    else
    {
      Assert(linitial_oid(schemas) == PG_CATALOG_NAMESPACE);
      result->addCatalog = true;
    }
    schemas = list_delete_first(schemas);
  }
  result->schemas = schemas;
  result->generation = activePathGeneration;

  MemoryContextSwitchTo(oldcxt);

  return result;
}

/*
 * CopySearchPathMatcher - copy the specified SearchPathMatcher.
 *
 * The result structure is allocated in CurrentMemoryContext.
 */
SearchPathMatcher *
CopySearchPathMatcher(SearchPathMatcher *path)
{
  SearchPathMatcher *result;

  result = (SearchPathMatcher *) palloc(sizeof(SearchPathMatcher));
  result->schemas = list_copy(path->schemas);
  result->addCatalog = path->addCatalog;
  result->addTemp = path->addTemp;
  result->generation = path->generation;

  return result;
}

/*
 * SearchPathMatchesCurrentEnvironment - does path match current environment?
 *
 * This is tested over and over in some common code paths, and in the typical
 * scenario where the active search path seldom changes, it'll always succeed.
 * We make that case fast by keeping a generation counter that is advanced
 * whenever the active search path changes.
 */
bool
SearchPathMatchesCurrentEnvironment(SearchPathMatcher *path)
{
  ListCell   *lc,
         *lcp;

  recomputeNamespacePath();

  /* Quick out if already known equal to active path. */
  if (path->generation == activePathGeneration)
    return true;

  /* We scan down the activeSearchPath to see if it matches the input. */
  lc = list_head(activeSearchPath);

  /* If path->addTemp, first item should be my temp namespace. */
  if (path->addTemp)
  {
    if (lc && lfirst_oid(lc) == myTempNamespace)
      lc = lnext(activeSearchPath, lc);
    else
      return false;
  }
  /* If path->addCatalog, next item should be pg_catalog. */
  if (path->addCatalog)
  {
    if (lc && lfirst_oid(lc) == PG_CATALOG_NAMESPACE)
      lc = lnext(activeSearchPath, lc);
    else
      return false;
  }
  /* We should now be looking at the activeCreationNamespace. */
  if (activeCreationNamespace != (lc ? lfirst_oid(lc) : InvalidOid))
    return false;
  /* The remainder of activeSearchPath should match path->schemas. */
  foreach(lcp, path->schemas)
  {
    if (lc && lfirst_oid(lc) == lfirst_oid(lcp))
      lc = lnext(activeSearchPath, lc);
    else
      return false;
  }
  if (lc)
    return false;

  /*
   * Update path->generation so that future tests will return quickly, so
   * long as the active search path doesn't change.
   */
  path->generation = activePathGeneration;

  return true;
}

/*
 * get_collation_oid - find a collation by possibly qualified name
 *
 * Note that this will only find collations that work with the current
 * database's encoding.
 */
Oid
get_collation_oid(List *collname, bool missing_ok)
{
  char     *schemaname;
  char     *collation_name;
  int32   dbencoding = GetDatabaseEncoding();
  Oid     namespaceId;
  Oid     colloid;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(collname, &schemaname, &collation_name);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (missing_ok && !OidIsValid(namespaceId))
      return InvalidOid;

    colloid = lookup_collation(collation_name, namespaceId, dbencoding);
    if (OidIsValid(colloid))
      return colloid;
  }
  else
  {
    /* search for it in search path */
    recomputeNamespacePath();

    foreach(l, activeSearchPath)
    {
      namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      colloid = lookup_collation(collation_name, namespaceId, dbencoding);
      if (OidIsValid(colloid))
        return colloid;
    }
  }

  /* Not found in path */
  if (!missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("collation \"%s\" for encoding \"%s\" does not exist",
            NameListToString(collname), GetDatabaseEncodingName())));
  return InvalidOid;
}

/*
 * get_conversion_oid - find a conversion by possibly qualified name
 */
Oid
get_conversion_oid(List *conname, bool missing_ok)
{
  char     *schemaname;
  char     *conversion_name;
  Oid     namespaceId;
  Oid     conoid = InvalidOid;
  ListCell   *l;

  /* deconstruct the name list */
  DeconstructQualifiedName(conname, &schemaname, &conversion_name);

  if (schemaname)
  {
    /* use exact schema given */
    namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
    if (missing_ok && !OidIsValid(namespaceId))
      conoid = InvalidOid;
    else
      conoid = GetSysCacheOid2(CONNAMENSP, Anum_pg_conversion_oid,
                   PointerGetDatum(conversion_name),
                   ObjectIdGetDatum(namespaceId));
  }
  else
  {
    /* search for it in search path */
    recomputeNamespacePath();

    foreach(l, activeSearchPath)
    {
      namespaceId = lfirst_oid(l);

      if (namespaceId == myTempNamespace)
        continue;   /* do not look in temp namespace */

      conoid = GetSysCacheOid2(CONNAMENSP, Anum_pg_conversion_oid,
                   PointerGetDatum(conversion_name),
                   ObjectIdGetDatum(namespaceId));
      if (OidIsValid(conoid))
        return conoid;
    }
  }

  /* Not found in path */
  if (!OidIsValid(conoid) && !missing_ok)
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("conversion \"%s\" does not exist",
            NameListToString(conname))));
  return conoid;
}

/*
 * FindDefaultConversionProc - find default encoding conversion proc
 */
Oid
FindDefaultConversionProc(int32 for_encoding, int32 to_encoding)
{
  Oid     proc;
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);

    if (namespaceId == myTempNamespace)
      continue;     /* do not look in temp namespace */

    proc = FindDefaultConversion(namespaceId, for_encoding, to_encoding);
    if (OidIsValid(proc))
      return proc;
  }

  /* Not found in path */
  return InvalidOid;
}

/*
 * Look up namespace IDs and perform ACL checks. Return newly-allocated list.
 */
static List *
preprocessNamespacePath(const char *searchPath, Oid roleid,
            bool *temp_missing)
{
  char     *rawname;
  List     *namelist;
  List     *oidlist;
  ListCell   *l;

  /* Need a modifiable copy */
  rawname = pstrdup(searchPath);

  /* Parse string into list of identifiers */
  if (!SplitIdentifierString(rawname, ',', &namelist))
  {
    /* syntax error in name list */
    /* this should not happen if GUC checked check_search_path */
    elog(ERROR, "invalid list syntax");
  }

  /*
   * Convert the list of names to a list of OIDs.  If any names are not
   * recognizable or we don't have read access, just leave them out of the
   * list.  (We can't raise an error, since the search_path setting has
   * already been accepted.)  Don't make duplicate entries, either.
   */
  oidlist = NIL;
  *temp_missing = false;
  foreach(l, namelist)
  {
    char     *curname = (char *) lfirst(l);
    Oid     namespaceId;

    if (strcmp(curname, "$user") == 0)
    {
      /* $user --- substitute namespace matching user name, if any */
      HeapTuple tuple;

      tuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(roleid));
      if (HeapTupleIsValid(tuple))
      {
        char     *rname;

        rname = NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname);
        namespaceId = get_namespace_oid(rname, true);
        ReleaseSysCache(tuple);
        if (OidIsValid(namespaceId) &&
          object_aclcheck(NamespaceRelationId, namespaceId, roleid,
                  ACL_USAGE) == ACLCHECK_OK)
          oidlist = lappend_oid(oidlist, namespaceId);
      }
    }
    else if (strcmp(curname, "pg_temp") == 0)
    {
      /* pg_temp --- substitute temp namespace, if any */
      if (OidIsValid(myTempNamespace))
        oidlist = lappend_oid(oidlist, myTempNamespace);
      else
      {
        /* If it ought to be the creation namespace, set flag */
        if (oidlist == NIL)
          *temp_missing = true;
      }
    }
    else
    {
      /* normal namespace reference */
      namespaceId = get_namespace_oid(curname, true);
      if (OidIsValid(namespaceId) &&
        object_aclcheck(NamespaceRelationId, namespaceId, roleid,
                ACL_USAGE) == ACLCHECK_OK)
        oidlist = lappend_oid(oidlist, namespaceId);
    }
  }

  pfree(rawname);
  list_free(namelist);

  return oidlist;
}

/*
 * Remove duplicates, run namespace search hooks, and prepend
 * implicitly-searched namespaces. Return newly-allocated list.
 *
 * If an object_access_hook is present, this must always be recalculated. It
 * may seem that duplicate elimination is not dependent on the result of the
 * hook, but if a hook returns different results on different calls for the
 * same namespace ID, then it could affect the order in which that namespace
 * appears in the final list.
 */
static List *
finalNamespacePath(List *oidlist, Oid *firstNS)
{
  List     *finalPath = NIL;
  ListCell   *lc;

  foreach(lc, oidlist)
  {
    Oid     namespaceId = lfirst_oid(lc);

    if (!list_member_oid(finalPath, namespaceId))
    {
      if (InvokeNamespaceSearchHook(namespaceId, false))
        finalPath = lappend_oid(finalPath, namespaceId);
    }
  }

  /*
   * Remember the first member of the explicit list.  (Note: this is
   * nominally wrong if temp_missing, but we need it anyway to distinguish
   * explicit from implicit mention of pg_catalog.)
   */
  if (finalPath == NIL)
    *firstNS = InvalidOid;
  else
    *firstNS = linitial_oid(finalPath);

  /*
   * Add any implicitly-searched namespaces to the list.  Note these go on
   * the front, not the back; also notice that we do not check USAGE
   * permissions for these.
   */
  if (!list_member_oid(finalPath, PG_CATALOG_NAMESPACE))
    finalPath = lcons_oid(PG_CATALOG_NAMESPACE, finalPath);

  if (OidIsValid(myTempNamespace) &&
    !list_member_oid(finalPath, myTempNamespace))
    finalPath = lcons_oid(myTempNamespace, finalPath);

  return finalPath;
}

/*
 * Retrieve search path information from the cache; or if not there, fill
 * it. The returned entry is valid only until the next call to this function.
 */
static const SearchPathCacheEntry *
cachedNamespacePath(const char *searchPath, Oid roleid)
{
  MemoryContext oldcxt;
  SearchPathCacheEntry *entry;

  spcache_init();

  entry = spcache_insert(searchPath, roleid);

  /*
   * An OOM may have resulted in a cache entry with missing 'oidlist' or
   * 'finalPath', so just compute whatever is missing.
   */

  if (entry->oidlist == NIL)
  {
    oldcxt = MemoryContextSwitchTo(SearchPathCacheContext);
    entry->oidlist = preprocessNamespacePath(searchPath, roleid,
                         &entry->temp_missing);
    MemoryContextSwitchTo(oldcxt);
  }

  /*
   * If a hook is set, we must recompute finalPath from the oidlist each
   * time, because the hook may affect the result. This is still much faster
   * than recomputing from the string (and doing catalog lookups and ACL
   * checks).
   */
  if (entry->finalPath == NIL || object_access_hook ||
    entry->forceRecompute)
  {
    list_free(entry->finalPath);
    entry->finalPath = NIL;

    oldcxt = MemoryContextSwitchTo(SearchPathCacheContext);
    entry->finalPath = finalNamespacePath(entry->oidlist,
                        &entry->firstNS);
    MemoryContextSwitchTo(oldcxt);

    /*
     * If an object_access_hook is set when finalPath is calculated, the
     * result may be affected by the hook. Force recomputation of
     * finalPath the next time this cache entry is used, even if the
     * object_access_hook is not set at that time.
     */
    entry->forceRecompute = object_access_hook ? true : false;
  }

  return entry;
}

/*
 * recomputeNamespacePath - recompute path derived variables if needed.
 */
static void
recomputeNamespacePath(void)
{
  Oid     roleid = GetUserId();
  bool    pathChanged;
  const SearchPathCacheEntry *entry;

  /* Do nothing if path is already valid. */
  if (baseSearchPathValid && namespaceUser == roleid)
    return;

  entry = cachedNamespacePath(namespace_search_path, roleid);

  if (baseCreationNamespace == entry->firstNS &&
    baseTempCreationPending == entry->temp_missing &&
    equal(entry->finalPath, baseSearchPath))
  {
    pathChanged = false;
  }
  else
  {
    MemoryContext oldcxt;
    List     *newpath;

    pathChanged = true;

    /* Must save OID list in permanent storage. */
    oldcxt = MemoryContextSwitchTo(TopMemoryContext);
    newpath = list_copy(entry->finalPath);
    MemoryContextSwitchTo(oldcxt);

    /* Now safe to assign to state variables. */
    list_free(baseSearchPath);
    baseSearchPath = newpath;
    baseCreationNamespace = entry->firstNS;
    baseTempCreationPending = entry->temp_missing;
  }

  /* Mark the path valid. */
  baseSearchPathValid = true;
  namespaceUser = roleid;

  /* And make it active. */
  activeSearchPath = baseSearchPath;
  activeCreationNamespace = baseCreationNamespace;
  activeTempCreationPending = baseTempCreationPending;

  /*
   * Bump the generation only if something actually changed.  (Notice that
   * what we compared to was the old state of the base path variables.)
   */
  if (pathChanged)
    activePathGeneration++;
}

/*
 * AccessTempTableNamespace
 *    Provide access to a temporary namespace, potentially creating it
 *    if not present yet.  This routine registers if the namespace gets
 *    in use in this transaction.  'force' can be set to true to allow
 *    the caller to enforce the creation of the temporary namespace for
 *    use in this backend, which happens if its creation is pending.
 */
static void
AccessTempTableNamespace(bool force)
{
  /*
   * Make note that this temporary namespace has been accessed in this
   * transaction.
   */
  MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPNAMESPACE;

  /*
   * If the caller attempting to access a temporary schema expects the
   * creation of the namespace to be pending and should be enforced, then go
   * through the creation.
   */
  if (!force && OidIsValid(myTempNamespace))
    return;

  /*
   * The temporary tablespace does not exist yet and is wanted, so
   * initialize it.
   */
  InitTempTableNamespace();
}

/*
 * InitTempTableNamespace
 *    Initialize temp table namespace on first use in a particular backend
 */
static void
InitTempTableNamespace(void)
{
  char    namespaceName[NAMEDATALEN];
  Oid     namespaceId;
  Oid     toastspaceId;

  Assert(!OidIsValid(myTempNamespace));

  /*
   * First, do permission check to see if we are authorized to make temp
   * tables.  We use a nonstandard error message here since "databasename:
   * permission denied" might be a tad cryptic.
   *
   * Note that ACL_CREATE_TEMP rights are rechecked in pg_namespace_aclmask;
   * that's necessary since current user ID could change during the session.
   * But there's no need to make the namespace in the first place until a
   * temp table creation request is made by someone with appropriate rights.
   */
  if (object_aclcheck(DatabaseRelationId, MyDatabaseId, GetUserId(),
            ACL_CREATE_TEMP) != ACLCHECK_OK)
    ereport(ERROR,
        (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
         errmsg("permission denied to create temporary tables in database \"%s\"",
            get_database_name(MyDatabaseId))));

  /*
   * Do not allow a Hot Standby session to make temp tables.  Aside from
   * problems with modifying the system catalogs, there is a naming
   * conflict: pg_temp_N belongs to the session with proc number N on the
   * primary, not to a hot standby session with the same proc number.  We
   * should not be able to get here anyway due to XactReadOnly checks, but
   * let's just make real sure.  Note that this also backstops various
   * operations that allow XactReadOnly transactions to modify temp tables;
   * they'd need RecoveryInProgress checks if not for this.
   */
  if (RecoveryInProgress())
    ereport(ERROR,
        (errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
         errmsg("cannot create temporary tables during recovery")));

  /* Parallel workers can't create temporary tables, either. */
  if (IsParallelWorker())
    ereport(ERROR,
        (errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
         errmsg("cannot create temporary tables during a parallel operation")));

  snprintf(namespaceName, sizeof(namespaceName), "pg_temp_%d", MyProcNumber);

  namespaceId = get_namespace_oid(namespaceName, true);
  if (!OidIsValid(namespaceId))
  {
    /*
     * First use of this temp namespace in this database; create it. The
     * temp namespaces are always owned by the superuser.  We leave their
     * permissions at default --- i.e., no access except to superuser ---
     * to ensure that unprivileged users can't peek at other backends'
     * temp tables.  This works because the places that access the temp
     * namespace for my own backend skip permissions checks on it.
     */
    namespaceId = NamespaceCreate(namespaceName, BOOTSTRAP_SUPERUSERID,
                    true);
    /* Advance command counter to make namespace visible */
    CommandCounterIncrement();
  }
  else
  {
    /*
     * If the namespace already exists, clean it out (in case the former
     * owner crashed without doing so).
     */
    RemoveTempRelations(namespaceId);
  }

  /*
   * If the corresponding toast-table namespace doesn't exist yet, create
   * it. (We assume there is no need to clean it out if it does exist, since
   * dropping a parent table should make its toast table go away.)
   */
  snprintf(namespaceName, sizeof(namespaceName), "pg_toast_temp_%d",
       MyProcNumber);

  toastspaceId = get_namespace_oid(namespaceName, true);
  if (!OidIsValid(toastspaceId))
  {
    toastspaceId = NamespaceCreate(namespaceName, BOOTSTRAP_SUPERUSERID,
                     true);
    /* Advance command counter to make namespace visible */
    CommandCounterIncrement();
  }

  /*
   * Okay, we've prepared the temp namespace ... but it's not committed yet,
   * so all our work could be undone by transaction rollback.  Set flag for
   * AtEOXact_Namespace to know what to do.
   */
  myTempNamespace = namespaceId;
  myTempToastNamespace = toastspaceId;

  /*
   * Mark MyProc as owning this namespace which other processes can use to
   * decide if a temporary namespace is in use or not.  We assume that
   * assignment of namespaceId is an atomic operation.  Even if it is not,
   * the temporary relation which resulted in the creation of this temporary
   * namespace is still locked until the current transaction commits, and
   * its pg_namespace row is not visible yet.  However it does not matter:
   * this flag makes the namespace as being in use, so no objects created on
   * it would be removed concurrently.
   */
  MyProc->tempNamespaceId = namespaceId;

  /* It should not be done already. */
  Assert(myTempNamespaceSubID == InvalidSubTransactionId);
  myTempNamespaceSubID = GetCurrentSubTransactionId();

  baseSearchPathValid = false;  /* need to rebuild list */
  searchPathCacheValid = false;
}

/*
 * End-of-transaction cleanup for namespaces.
 */
void
AtEOXact_Namespace(bool isCommit, bool parallel)
{
  /*
   * If we abort the transaction in which a temp namespace was selected,
   * we'll have to do any creation or cleanout work over again.  So, just
   * forget the namespace entirely until next time.  On the other hand, if
   * we commit then register an exit callback to clean out the temp tables
   * at backend shutdown.  (We only want to register the callback once per
   * session, so this is a good place to do it.)
   */
  if (myTempNamespaceSubID != InvalidSubTransactionId && !parallel)
  {
    if (isCommit)
      before_shmem_exit(RemoveTempRelationsCallback, 0);
    else
    {
      myTempNamespace = InvalidOid;
      myTempToastNamespace = InvalidOid;
      baseSearchPathValid = false;  /* need to rebuild list */
      searchPathCacheValid = false;

      /*
       * Reset the temporary namespace flag in MyProc.  We assume that
       * this operation is atomic.
       *
       * Because this transaction is aborting, the pg_namespace row is
       * not visible to anyone else anyway, but that doesn't matter:
       * it's not a problem if objects contained in this namespace are
       * removed concurrently.
       */
      MyProc->tempNamespaceId = InvalidOid;
    }
    myTempNamespaceSubID = InvalidSubTransactionId;
  }

}

/*
 * AtEOSubXact_Namespace
 *
 * At subtransaction commit, propagate the temp-namespace-creation
 * flag to the parent subtransaction.
 *
 * At subtransaction abort, forget the flag if we set it up.
 */
void
AtEOSubXact_Namespace(bool isCommit, SubTransactionId mySubid,
            SubTransactionId parentSubid)
{

  if (myTempNamespaceSubID == mySubid)
  {
    if (isCommit)
      myTempNamespaceSubID = parentSubid;
    else
    {
      myTempNamespaceSubID = InvalidSubTransactionId;
      /* TEMP namespace creation failed, so reset state */
      myTempNamespace = InvalidOid;
      myTempToastNamespace = InvalidOid;
      baseSearchPathValid = false;  /* need to rebuild list */
      searchPathCacheValid = false;

      /*
       * Reset the temporary namespace flag in MyProc.  We assume that
       * this operation is atomic.
       *
       * Because this subtransaction is aborting, the pg_namespace row
       * is not visible to anyone else anyway, but that doesn't matter:
       * it's not a problem if objects contained in this namespace are
       * removed concurrently.
       */
      MyProc->tempNamespaceId = InvalidOid;
    }
  }
}

/*
 * Remove all relations in the specified temp namespace.
 *
 * This is called at backend shutdown (if we made any temp relations).
 * It is also called when we begin using a pre-existing temp namespace,
 * in order to clean out any relations that might have been created by
 * a crashed backend.
 */
static void
RemoveTempRelations(Oid tempNamespaceId)
{
  ObjectAddress object;

  /*
   * We want to get rid of everything in the target namespace, but not the
   * namespace itself (deleting it only to recreate it later would be a
   * waste of cycles).  Hence, specify SKIP_ORIGINAL.  It's also an INTERNAL
   * deletion, and we want to not drop any extensions that might happen to
   * own temp objects.
   */
  object.classId = NamespaceRelationId;
  object.objectId = tempNamespaceId;
  object.objectSubId = 0;

  performDeletion(&object, DROP_CASCADE,
          PERFORM_DELETION_INTERNAL |
          PERFORM_DELETION_QUIETLY |
          PERFORM_DELETION_SKIP_ORIGINAL |
          PERFORM_DELETION_SKIP_EXTENSIONS);
}

/*
 * Callback to remove temp relations at backend exit.
 */
static void
RemoveTempRelationsCallback(int code, Datum arg)
{
  if (OidIsValid(myTempNamespace))  /* should always be true */
  {
    /* Need to ensure we have a usable transaction. */
    AbortOutOfAnyTransaction();
    StartTransactionCommand();
    PushActiveSnapshot(GetTransactionSnapshot());

    RemoveTempRelations(myTempNamespace);

    PopActiveSnapshot();
    CommitTransactionCommand();
  }
}

/*
 * Remove all temp tables from the temporary namespace.
 */
void
ResetTempTableNamespace(void)
{
  if (OidIsValid(myTempNamespace))
    RemoveTempRelations(myTempNamespace);
}


/*
 * Routines for handling the GUC variable 'search_path'.
 */

/* check_hook: validate new search_path value */
bool
check_search_path(char **newval, void **extra, GucSource source)
{
  Oid     roleid = InvalidOid;
  const char *searchPath = *newval;
  char     *rawname;
  List     *namelist;
  bool    use_cache = (SearchPathCacheContext != NULL);

  /*
   * We used to try to check that the named schemas exist, but there are
   * many valid use-cases for having search_path settings that include
   * schemas that don't exist; and often, we are not inside a transaction
   * here and so can't consult the system catalogs anyway.  So now, the only
   * requirement is syntactic validity of the identifier list.
   *
   * Checking only the syntactic validity also allows us to use the search
   * path cache (if available) to avoid calling SplitIdentifierString() on
   * the same string repeatedly.
   */
  if (use_cache)
  {
    spcache_init();

    roleid = GetUserId();

    if (spcache_lookup(searchPath, roleid) != NULL)
      return true;
  }

  /*
   * Ensure validity check succeeds before creating cache entry.
   */

  rawname = pstrdup(searchPath);  /* need a modifiable copy */

  /* Parse string into list of identifiers */
  if (!SplitIdentifierString(rawname, ',', &namelist))
  {
    /* syntax error in name list */
    GUC_check_errdetail("List syntax is invalid.");
    pfree(rawname);
    list_free(namelist);
    return false;
  }
  pfree(rawname);
  list_free(namelist);

  /* OK to create empty cache entry */
  if (use_cache)
    (void) spcache_insert(searchPath, roleid);

  return true;
}

/* assign_hook: do extra actions as needed */
void
assign_search_path(const char *newval, void *extra)
{
  /* don't access search_path during bootstrap */
  Assert(!IsBootstrapProcessingMode());

  /*
   * We mark the path as needing recomputation, but don't do anything until
   * it's needed.  This avoids trying to do database access during GUC
   * initialization, or outside a transaction.
   *
   * This does not invalidate the search path cache, so if this value had
   * been previously set and no syscache invalidations happened,
   * recomputation may not be necessary.
   */
  baseSearchPathValid = false;
}

/*
 * InitializeSearchPath: initialize module during InitPostgres.
 *
 * This is called after we are up enough to be able to do catalog lookups.
 */
void
InitializeSearchPath(void)
{
  if (IsBootstrapProcessingMode())
  {
    /*
     * In bootstrap mode, the search path must be 'pg_catalog' so that
     * tables are created in the proper namespace; ignore the GUC setting.
     */
    MemoryContext oldcxt;

    oldcxt = MemoryContextSwitchTo(TopMemoryContext);
    baseSearchPath = list_make1_oid(PG_CATALOG_NAMESPACE);
    MemoryContextSwitchTo(oldcxt);
    baseCreationNamespace = PG_CATALOG_NAMESPACE;
    baseTempCreationPending = false;
    baseSearchPathValid = true;
    namespaceUser = GetUserId();
    activeSearchPath = baseSearchPath;
    activeCreationNamespace = baseCreationNamespace;
    activeTempCreationPending = baseTempCreationPending;
    activePathGeneration++; /* pro forma */
  }
  else
  {
    /*
     * In normal mode, arrange for a callback on any syscache invalidation
     * that will affect the search_path cache.
     */

    /* namespace name or ACLs may have changed */
    CacheRegisterSyscacheCallback(NAMESPACEOID,
                    InvalidationCallback,
                    (Datum) 0);

    /* role name may affect the meaning of "$user" */
    CacheRegisterSyscacheCallback(AUTHOID,
                    InvalidationCallback,
                    (Datum) 0);

    /* role membership may affect ACLs */
    CacheRegisterSyscacheCallback(AUTHMEMROLEMEM,
                    InvalidationCallback,
                    (Datum) 0);

    /* database owner may affect ACLs */
    CacheRegisterSyscacheCallback(DATABASEOID,
                    InvalidationCallback,
                    (Datum) 0);

    /* Force search path to be recomputed on next use */
    baseSearchPathValid = false;
    searchPathCacheValid = false;
  }
}

/*
 * InvalidationCallback
 *    Syscache inval callback function
 */
static void
InvalidationCallback(Datum arg, int cacheid, uint32 hashvalue)
{
  /*
   * Force search path to be recomputed on next use, also invalidating the
   * search path cache (because namespace names, ACLs, or role names may
   * have changed).
   */
  baseSearchPathValid = false;
  searchPathCacheValid = false;
}

/*
 * Fetch the active search path. The return value is a palloc'ed list
 * of OIDs; the caller is responsible for freeing this storage as
 * appropriate.
 *
 * The returned list includes the implicitly-prepended namespaces only if
 * includeImplicit is true.
 *
 * Note: calling this may result in a CommandCounterIncrement operation,
 * if we have to create or clean out the temp namespace.
 */
List *
fetch_search_path(bool includeImplicit)
{
  List     *result;

  recomputeNamespacePath();

  /*
   * If the temp namespace should be first, force it to exist.  This is so
   * that callers can trust the result to reflect the actual default
   * creation namespace.  It's a bit bogus to do this here, since
   * current_schema() is supposedly a stable function without side-effects,
   * but the alternatives seem worse.
   */
  if (activeTempCreationPending)
  {
    AccessTempTableNamespace(true);
    recomputeNamespacePath();
  }

  result = list_copy(activeSearchPath);
  if (!includeImplicit)
  {
    while (result && linitial_oid(result) != activeCreationNamespace)
      result = list_delete_first(result);
  }

  return result;
}

/*
 * Fetch the active search path into a caller-allocated array of OIDs.
 * Returns the number of path entries.  (If this is more than sarray_len,
 * then the data didn't fit and is not all stored.)
 *
 * The returned list always includes the implicitly-prepended namespaces,
 * but never includes the temp namespace.  (This is suitable for existing
 * users, which would want to ignore the temp namespace anyway.)  This
 * definition allows us to not worry about initializing the temp namespace.
 */
int
fetch_search_path_array(Oid *sarray, int sarray_len)
{
  int     count = 0;
  ListCell   *l;

  recomputeNamespacePath();

  foreach(l, activeSearchPath)
  {
    Oid     namespaceId = lfirst_oid(l);

    if (namespaceId == myTempNamespace)
      continue;     /* do not include temp namespace */

    if (count < sarray_len)
      sarray[count] = namespaceId;
    count++;
  }

  return count;
}


/*
 * Export the FooIsVisible functions as SQL-callable functions.
 *
 * Note: as of Postgres 8.4, these will silently return NULL if called on
 * a nonexistent object OID, rather than failing.  This is to avoid race
 * condition errors when a query that's scanning a catalog using an MVCC
 * snapshot uses one of these functions.  The underlying IsVisible functions
 * always use an up-to-date snapshot and so might see the object as already
 * gone when it's still visible to the transaction snapshot.
 */

Datum
pg_table_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = RelationIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_type_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = TypeIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_function_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = FunctionIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_operator_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = OperatorIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_opclass_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = OpclassIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_opfamily_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = OpfamilyIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_collation_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = CollationIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_conversion_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = ConversionIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_statistics_obj_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = StatisticsObjIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_ts_parser_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = TSParserIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_ts_dict_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = TSDictionaryIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_ts_template_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = TSTemplateIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_ts_config_is_visible(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);
  bool    result;
  bool    is_missing = false;

  result = TSConfigIsVisibleExt(oid, &is_missing);

  if (is_missing)
    PG_RETURN_NULL();
  PG_RETURN_BOOL(result);
}

Datum
pg_my_temp_schema(PG_FUNCTION_ARGS)
{
  PG_RETURN_OID(myTempNamespace);
}

Datum
pg_is_other_temp_schema(PG_FUNCTION_ARGS)
{
  Oid     oid = PG_GETARG_OID(0);

  PG_RETURN_BOOL(isOtherTempNamespace(oid));
}

Coverage Report

Created: 2025-06-15 06:31