* postinit.c
* postgres initialization utilities
*
- * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/init/postinit.c,v 1.82 2001/03/22 04:00:00 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/init/postinit.c,v 1.159 2005/11/22 18:17:26 momjian Exp $
*
*
*-------------------------------------------------------------------------
#include <fcntl.h>
#include <sys/file.h>
-#include <sys/types.h>
#include <math.h>
#include <unistd.h>
-#ifndef OLD_FILE_NAMING
-#include "catalog/catalog.h"
-#endif
-
+#include "access/genam.h"
#include "access/heapam.h"
-#include "catalog/catname.h"
+#include "catalog/catalog.h"
+#include "catalog/indexing.h"
+#include "catalog/namespace.h"
+#include "catalog/pg_authid.h"
#include "catalog/pg_database.h"
-#include "commands/trigger.h"
-#include "commands/variable.h" /* for set_default_client_encoding() */
+#include "catalog/pg_tablespace.h"
+#include "libpq/hba.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
+#include "postmaster/autovacuum.h"
+#include "postmaster/postmaster.h"
#include "storage/backendid.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
#include "storage/proc.h"
+#include "storage/procarray.h"
#include "storage/sinval.h"
#include "storage/smgr.h"
+#include "utils/acl.h"
+#include "utils/flatfiles.h"
#include "utils/fmgroids.h"
+#include "utils/guc.h"
#include "utils/portal.h"
#include "utils/relcache.h"
#include "utils/syscache.h"
-#include "utils/temprel.h"
+#include "pgstat.h"
+static bool FindMyDatabase(const char *name, Oid *db_id, Oid *db_tablespace);
static void ReverifyMyDatabase(const char *name);
static void InitCommunication(void);
-static void ShutdownPostgres(void);
-
-int lockingOff = 0; /* backend -L switch */
+static void ShutdownPostgres(int code, Datum arg);
+static bool ThereIsAtLeastOneRole(void);
/*** InitPostgres support ***/
-/* --------------------------------
- * ReverifyMyDatabase
+/*
+ * FindMyDatabase -- get the critical info needed to locate my database
+ *
+ * Find the named database in pg_database, return its database OID and the
+ * OID of its default tablespace. Return TRUE if found, FALSE if not.
+ *
+ * Since we are not yet up and running as a backend, we cannot look directly
+ * at pg_database (we can't obtain locks nor participate in transactions).
+ * So to get the info we need before starting up, we must look at the "flat
+ * file" copy of pg_database that is helpfully maintained by flatfiles.c.
+ * This is subject to various race conditions, so after we have the
+ * transaction infrastructure started, we have to recheck the information;
+ * see ReverifyMyDatabase.
+ */
+static bool
+FindMyDatabase(const char *name, Oid *db_id, Oid *db_tablespace)
+{
+ bool result = false;
+ char *filename;
+ FILE *db_file;
+ char thisname[NAMEDATALEN];
+ TransactionId dummyxid;
+
+ filename = database_getflatfilename();
+ db_file = AllocateFile(filename, "r");
+ if (db_file == NULL)
+ ereport(FATAL,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m", filename)));
+
+ while (read_pg_database_line(db_file, thisname, db_id,
+ db_tablespace, &dummyxid,
+ &dummyxid))
+ {
+ if (strcmp(thisname, name) == 0)
+ {
+ result = true;
+ break;
+ }
+ }
+
+ FreeFile(db_file);
+ pfree(filename);
+
+ return result;
+}
+
+/*
+ * ReverifyMyDatabase -- recheck info obtained by FindMyDatabase
*
- * Since we are forced to fetch the database OID out of pg_database without
- * benefit of locking or transaction ID checking (see utils/misc/database.c),
- * we might have gotten a wrong answer. Or, we might have attached to a
- * database that's in process of being destroyed by destroydb(). This
- * routine is called after we have all the locking and other infrastructure
- * running --- now we can check that we are really attached to a valid
- * database.
+ * Since FindMyDatabase cannot lock pg_database, the information it read
+ * could be stale; for example we might have attached to a database that's in
+ * process of being destroyed by dropdb(). This routine is called after
+ * we have all the locking and other infrastructure running --- now we can
+ * check that we are really attached to a valid database.
*
- * In reality, if destroydb() is running in parallel with our startup,
+ * In reality, if dropdb() is running in parallel with our startup,
* it's pretty likely that we will have failed before now, due to being
* unable to read some of the system tables within the doomed database.
* This routine just exists to make *sure* we have not started up in an
* creating any serious problems.
*
* This is also a handy place to fetch the database encoding info out
- * of pg_database, if we are in MULTIBYTE mode.
- * --------------------------------
+ * of pg_database.
+ *
+ * To avoid having to read pg_database more times than necessary
+ * during session startup, this place is also fitting to set up any
+ * database-specific configuration variables.
*/
static void
ReverifyMyDatabase(const char *name)
{
Relation pgdbrel;
- HeapScanDesc pgdbscan;
+ SysScanDesc pgdbscan;
ScanKeyData key;
HeapTuple tup;
Form_pg_database dbform;
/*
- * Because we grab AccessShareLock here, we can be sure that destroydb
- * is not running in parallel with us (any more).
+ * Because we grab RowShareLock here, we can be sure that dropdb() is not
+ * running in parallel with us (any more).
*/
- pgdbrel = heap_openr(DatabaseRelationName, AccessShareLock);
+ pgdbrel = heap_open(DatabaseRelationId, RowShareLock);
- ScanKeyEntryInitialize(&key, 0, Anum_pg_database_datname,
- F_NAMEEQ, NameGetDatum(name));
+ ScanKeyInit(&key,
+ Anum_pg_database_datname,
+ BTEqualStrategyNumber, F_NAMEEQ,
+ NameGetDatum(name));
- pgdbscan = heap_beginscan(pgdbrel, 0, SnapshotNow, 1, &key);
+ pgdbscan = systable_beginscan(pgdbrel, DatabaseNameIndexId, true,
+ SnapshotNow, 1, &key);
- tup = heap_getnext(pgdbscan, 0);
+ tup = systable_getnext(pgdbscan);
if (!HeapTupleIsValid(tup) ||
- tup->t_data->t_oid != MyDatabaseId)
+ HeapTupleGetOid(tup) != MyDatabaseId)
{
/* OOPS */
- heap_close(pgdbrel, AccessShareLock);
+ heap_close(pgdbrel, RowShareLock);
/*
- * The only real problem I could have created is to load dirty
- * buffers for the dead database into shared buffer cache; if I
- * did, some other backend will eventually try to write them and
- * die in mdblindwrt. Flush any such pages to forestall trouble.
+ * The only real problem I could have created is to load dirty buffers
+ * for the dead database into shared buffer cache; if I did, some
+ * other backend will eventually try to write them and die in
+ * mdblindwrt. Flush any such pages to forestall trouble.
*/
DropBuffers(MyDatabaseId);
/* Now I can commit hara-kiri with a clear conscience... */
- elog(FATAL, "Database \"%s\", OID %u, has disappeared from pg_database",
- name, MyDatabaseId);
+ ereport(FATAL,
+ (errcode(ERRCODE_UNDEFINED_DATABASE),
+ errmsg("database \"%s\", OID %u, has disappeared from pg_database",
+ name, MyDatabaseId)));
}
+ dbform = (Form_pg_database) GETSTRUCT(tup);
+
/*
- * Also check that the database is currently allowing connections.
+ * These next checks are not enforced when in standalone mode, so that
+ * there is a way to recover from disabling all access to all databases,
+ * for example "UPDATE pg_database SET datallowconn = false;".
+ *
+ * We do not enforce them for the autovacuum process either.
*/
- dbform = (Form_pg_database) GETSTRUCT(tup);
- if (!dbform->datallowconn)
- elog(FATAL, "Database \"%s\" is not currently accepting connections",
- name);
+ if (IsUnderPostmaster && !IsAutoVacuumProcess())
+ {
+ /*
+ * Check that the database is currently allowing connections.
+ */
+ if (!dbform->datallowconn)
+ ereport(FATAL,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("database \"%s\" is not currently accepting connections",
+ name)));
+
+ /*
+ * Check connection limit for this database.
+ *
+ * There is a race condition here --- we create our PGPROC before
+ * checking for other PGPROCs. If two backends did this at about the
+ * same time, they might both think they were over the limit, while
+ * ideally one should succeed and one fail. Getting that to work
+ * exactly seems more trouble than it is worth, however; instead we
+ * just document that the connection limit is approximate.
+ */
+ if (dbform->datconnlimit >= 0 &&
+ !superuser() &&
+ CountDBBackends(MyDatabaseId) > dbform->datconnlimit)
+ ereport(FATAL,
+ (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
+ errmsg("too many connections for database \"%s\"",
+ name)));
+ }
/*
- * OK, we're golden. Only other to-do item is to save the MULTIBYTE
- * encoding info out of the pg_database tuple --- or complain, if we
- * can't support it.
+ * OK, we're golden. Next to-do item is to save the encoding info out of
+ * the pg_database tuple.
*/
-#ifdef MULTIBYTE
SetDatabaseEncoding(dbform->encoding);
-#else
- if (dbform->encoding != SQL_ASCII)
- elog(FATAL, "database was initialized with MULTIBYTE encoding %d,\n\tbut the backend was compiled without multibyte support.\n\tlooks like you need to initdb or recompile.",
- dbform->encoding);
-#endif
+ /* Record it as a GUC internal option, too */
+ SetConfigOption("server_encoding", GetDatabaseEncodingName(),
+ PGC_INTERNAL, PGC_S_OVERRIDE);
+ /* If we have no other source of client_encoding, use server encoding */
+ SetConfigOption("client_encoding", GetDatabaseEncodingName(),
+ PGC_BACKEND, PGC_S_DEFAULT);
+
+ /*
+ * Lastly, set up any database-specific configuration variables.
+ */
+ if (IsUnderPostmaster)
+ {
+ Datum datum;
+ bool isnull;
+
+ datum = heap_getattr(tup, Anum_pg_database_datconfig,
+ RelationGetDescr(pgdbrel), &isnull);
+ if (!isnull)
+ {
+ ArrayType *a = DatumGetArrayTypeP(datum);
+
+ ProcessGUCArray(a, PGC_S_DATABASE);
+ }
+ }
- heap_endscan(pgdbscan);
- heap_close(pgdbrel, AccessShareLock);
+ systable_endscan(pgdbscan);
+ heap_close(pgdbrel, RowShareLock);
}
static void
InitCommunication(void)
{
- /* ----------------
- * initialize shared memory and semaphores appropriately.
- * ----------------
+ /*
+ * initialize shared memory and semaphores appropriately.
*/
if (!IsUnderPostmaster) /* postmaster already did this */
{
- /* ----------------
- * we're running a postgres backend by itself with
- * no front end or postmaster. Create private "shmem"
- * and semaphores. Setting MaxBackends = 16 is arbitrary.
- * ----------------
+ /*
+ * We're running a postgres bootstrap process or a standalone backend.
+ * Create private "shmem" and semaphores.
*/
- CreateSharedMemoryAndSemaphores(true, 16);
+ CreateSharedMemoryAndSemaphores(true, 0);
}
}
/*
* Early initialization of a backend (either standalone or under postmaster).
* This happens even before InitPostgres.
+ *
+ * If you're wondering why this is separate from InitPostgres at all:
+ * the critical distinction is that this stuff has to happen before we can
+ * run XLOG-related initialization, which is done before InitPostgres --- in
+ * fact, for cases such as checkpoint creation processes, InitPostgres may
+ * never be done at all.
*/
void
BaseInit(void)
{
-
/*
* Attach to shared memory and semaphores, and initialize our
* input/output/debugging file descriptors.
InitCommunication();
DebugFileOpen();
- /* Do local initialization of storage and buffer managers */
+ /* Do local initialization of file, storage and buffer managers */
+ InitFileAccess();
smgrinit();
InitBufferPoolAccess();
- InitLocalBuffer();
-
- EnablePortalManager(); /* memory for portal/transaction stuff */
}
* InitPostgres
* Initialize POSTGRES.
*
+ * In bootstrap mode neither of the parameters are used. In autovacuum
+ * mode, the username parameter is not used.
+ *
+ * The return value indicates whether the userID is a superuser. (That
+ * can only be tested inside a transaction, so we want to do it during
+ * the startup transaction rather than doing a separate one in postgres.c.)
+ *
* Note:
* Be very careful with the order of calls in the InitPostgres function.
* --------------------------------
*/
-void
+bool
InitPostgres(const char *dbname, const char *username)
{
bool bootstrap = IsBootstrapProcessingMode();
+ bool autovacuum = IsAutoVacuumProcess();
+ bool am_superuser;
- SetDatabaseName(dbname);
-
- /* ----------------
- * initialize the database id used for system caches and lock tables
- * ----------------
+ /*
+ * Set up the global variables holding database id and path.
+ *
+ * We take a shortcut in the bootstrap case, otherwise we have to look up
+ * the db name in pg_database.
*/
if (bootstrap)
{
MyDatabaseId = TemplateDbOid;
- SetDatabasePath(GetDatabasePath(MyDatabaseId));
- LockDisable(true);
+ MyDatabaseTableSpace = DEFAULTTABLESPACE_OID;
+ SetDatabasePath(GetDatabasePath(MyDatabaseId, MyDatabaseTableSpace));
}
else
{
- char *fullpath,
- datpath[MAXPGPATH];
-
- /* Verify if DataDir is ok */
- if (access(DataDir, F_OK) == -1)
- elog(FATAL, "Database system not found.\n\t"
- "Data directory '%s' does not exist.",
- DataDir);
+ char *fullpath;
- ValidatePgVersion(DataDir);
+ /*
+ * Formerly we validated DataDir here, but now that's done earlier.
+ */
/*
- * Find oid and path of the database we're about to open. Since
+ * Find oid and tablespace of the database we're about to open. Since
* we're not yet up and running we have to use the hackish
- * GetRawDatabaseInfo.
+ * FindMyDatabase.
*/
- GetRawDatabaseInfo(dbname, &MyDatabaseId, datpath);
-
- if (!OidIsValid(MyDatabaseId))
- elog(FATAL,
- "Database \"%s\" does not exist in the system catalog.",
- dbname);
+ if (!FindMyDatabase(dbname, &MyDatabaseId, &MyDatabaseTableSpace))
+ ereport(FATAL,
+ (errcode(ERRCODE_UNDEFINED_DATABASE),
+ errmsg("database \"%s\" does not exist",
+ dbname)));
- fullpath = GetDatabasePath(MyDatabaseId);
+ fullpath = GetDatabasePath(MyDatabaseId, MyDatabaseTableSpace);
/* Verify the database path */
if (access(fullpath, F_OK) == -1)
- elog(FATAL, "Database \"%s\" does not exist.\n\t"
- "The database subdirectory '%s' is missing.",
- dbname, fullpath);
+ {
+ if (errno == ENOENT)
+ ereport(FATAL,
+ (errcode(ERRCODE_UNDEFINED_DATABASE),
+ errmsg("database \"%s\" does not exist",
+ dbname),
+ errdetail("The database subdirectory \"%s\" is missing.",
+ fullpath)));
+ else
+ ereport(FATAL,
+ (errcode_for_file_access(),
+ errmsg("could not access directory \"%s\": %m",
+ fullpath)));
+ }
ValidatePgVersion(fullpath);
- if (chdir(fullpath) == -1)
- elog(FATAL, "Unable to change directory to '%s': %m", fullpath);
-
SetDatabasePath(fullpath);
}
*/
/*
- * Initialize the transaction system and the relation descriptor
- * cache. Note we have to make certain the lock manager is off while
- * we do this.
- */
- AmiTransactionOverride(IsBootstrapProcessingMode());
- LockDisable(true);
-
- /*
- * Part of the initialization processing done here sets a read lock on
- * pg_log. Since locking is disabled the set doesn't have intended
- * effect of locking out writers, but this is ok, since we only lock
- * it to examine AMI transaction status, and this is never written
- * after initdb is done. -mer 15 June 1992
- */
- RelationCacheInitialize(); /* pre-allocated reldescs created here */
-
- InitializeTransactionSystem(); /* pg_log,etc init/crash recovery
- * here */
-
- LockDisable(false);
-
- /*
- * Set up my per-backend PROC struct in shared memory.
+ * Set up my per-backend PGPROC struct in shared memory. (We need to
+ * know MyDatabaseId before we can do this, since it's entered into the
+ * PGPROC struct.)
*/
InitProcess();
/*
* Initialize my entry in the shared-invalidation manager's array of
- * per-backend data. (Formerly this came before InitProcess, but now
- * it must happen after, because it uses MyProc.) Once I have done
- * this, I am visible to other backends!
+ * per-backend data. (Formerly this came before InitProcess, but now it
+ * must happen after, because it uses MyProc.) Once I have done this, I
+ * am visible to other backends!
*
* Sets up MyBackendId, a unique backend identifier.
*/
InitBackendSharedInvalidationState();
- if (MyBackendId > MAXBACKENDS || MyBackendId <= 0)
- elog(FATAL, "cinit2: bad backend id %d", MyBackendId);
+ if (MyBackendId > MaxBackends || MyBackendId <= 0)
+ elog(FATAL, "bad backend id: %d", MyBackendId);
/*
- * Initialize the access methods. Does not touch files (?) - thomas
- * 1997-11-01
+ * bufmgr needs another initialization call too
*/
- initam();
+ InitBufferPoolBackend();
/*
- * Initialize all the system catalog caches.
- *
- * Does not touch files since all routines are builtins (?) - thomas
- * 1997-11-01
+ * Initialize local process's access to XLOG. In bootstrap case we may
+ * skip this since StartupXLOG() was run instead.
+ */
+ if (!bootstrap)
+ InitXLOGAccess();
+
+ /*
+ * Initialize the relation descriptor cache. This must create at least
+ * the minimum set of "nailed-in" cache entries. No catalog access
+ * happens here.
+ */
+ RelationCacheInitialize();
+
+ /*
+ * Initialize all the system catalog caches. Note that no catalog access
+ * happens here; we only set up the cache structure.
*/
InitCatalogCache();
+ /* Initialize portal manager */
+ EnablePortalManager();
+
/*
- * Initialize the deferred trigger manager --- must happen before
- * first transaction start.
+ * Set up process-exit callback to do pre-shutdown cleanup. This has to
+ * be after we've initialized all the low-level modules like the buffer
+ * manager, because during shutdown this has to run before the low-level
+ * modules start to close down. On the other hand, we want it in place
+ * before we begin our first transaction --- if we fail during the
+ * initialization transaction, as is entirely possible, we need the
+ * AbortTransaction call to clean up.
*/
- DeferredTriggerInit();
+ on_shmem_exit(ShutdownPostgres, 0);
/* start a new transaction here before access to db */
if (!bootstrap)
StartTransactionCommand();
- /* replace faked-up relcache entries with the real info */
+ /*
+ * It's now possible to do real access to the system catalogs.
+ *
+ * Replace faked-up relcache entries with correct info.
+ */
RelationCacheInitializePhase2();
- if (lockingOff)
- LockDisable(true);
-
/*
- * Set ourselves to the proper user id and figure out our postgres
- * user id.
+ * Figure out our postgres user id. In standalone mode and in the
+ * autovacuum process, we use a fixed id, otherwise we figure it out from
+ * the authenticated user name.
*/
- if (bootstrap)
- SetSessionUserId(geteuid());
+ if (bootstrap || autovacuum)
+ InitializeSessionUserIdStandalone();
+ else if (!IsUnderPostmaster)
+ {
+ InitializeSessionUserIdStandalone();
+ if (!ThereIsAtLeastOneRole())
+ ereport(WARNING,
+ (errcode(ERRCODE_UNDEFINED_OBJECT),
+ errmsg("no roles are defined in this database system"),
+ errhint("You should immediately run CREATE USER \"%s\" CREATEUSER;.",
+ username)));
+ }
else
- SetSessionUserIdFromUserName(username);
-
- setuid(geteuid());
+ {
+ /* normal multiuser case */
+ InitializeSessionUserId(username);
+ }
/*
- * Unless we are bootstrapping, double-check that InitMyDatabaseInfo()
- * got a correct result. We can't do this until all the
- * database-access infrastructure is up.
+ * Unless we are bootstrapping, double-check that InitMyDatabaseInfo() got
+ * a correct result. We can't do this until all the database-access
+ * infrastructure is up. (Also, it wants to know if the user is a
+ * superuser, so the above stuff has to happen first.)
*/
if (!bootstrap)
ReverifyMyDatabase(dbname);
-#ifdef MULTIBYTE
- /* set default client encoding --- uses info from ReverifyMyDatabase */
- set_default_client_encoding();
-#endif
+ /*
+ * Final phase of relation cache startup: write a new cache file if
+ * necessary. This is done after ReverifyMyDatabase to avoid writing a
+ * cache file into a dead database.
+ */
+ RelationCacheInitializePhase3();
/*
- * Set up process-exit callbacks to remove temp relations and then do
- * pre-shutdown cleanup. This should be last because we want
- * shmem_exit to call these routines before the exit callbacks that
- * are registered by buffer manager, lock manager, etc. We need to
- * run this code before we close down database access!
+ * Check if user is a superuser.
*/
- on_shmem_exit(ShutdownPostgres, 0);
+ if (bootstrap || autovacuum)
+ am_superuser = true;
+ else
+ am_superuser = superuser();
+
+ /*
+ * Check a normal user hasn't connected to a superuser reserved slot.
+ */
+ if (!am_superuser &&
+ ReservedBackends > 0 &&
+ !HaveNFreeProcs(ReservedBackends))
+ ereport(FATAL,
+ (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
+ errmsg("connection limit exceeded for non-superusers")));
/*
- * because callbacks are called in reverse order, this gets done
- * first:
+ * Initialize various default states that can't be set up until we've
+ * selected the active user and done ReverifyMyDatabase.
*/
- on_shmem_exit(remove_all_temp_relations, 0);
+
+ /* set default namespace search path */
+ InitializeSearchPath();
+
+ /* set up ACL framework (currently just sets RolMemCache callback) */
+ initialize_acl();
+
+ /* initialize client encoding */
+ InitializeClientEncoding();
+
+ /* initialize statistics collection for this backend */
+ if (IsUnderPostmaster)
+ pgstat_bestart();
/* close the transaction we started above */
if (!bootstrap)
CommitTransactionCommand();
+
+ return am_superuser;
}
+
/*
* Backend-shutdown callback. Do cleanup that we want to be sure happens
* before all the supporting modules begin to nail their doors shut via
- * their own callbacks. Note that because this has to be registered very
- * late in startup, it will not get called if we suffer a failure *during*
- * startup.
+ * their own callbacks.
*
* User-level cleanup, such as temp-relation removal and UNLISTEN, happens
* via separate callbacks that execute before this one. We don't combine the
* cleanup fails.
*/
static void
-ShutdownPostgres(void)
+ShutdownPostgres(int code, Datum arg)
{
+ /* Make sure we've killed any active transaction */
+ AbortOutOfAnyTransaction();
/*
- * These operations are really just a minimal subset of
- * AbortTransaction(). We don't want to do any inessential cleanup,
- * since that just raises the odds of failure --- but there's some
- * stuff we need to do.
- *
- * Release any spinlocks or buffer context locks we might be holding.
- * This is a kluge to improve the odds that we won't get into a
- * self-made stuck-spinlock scenario while trying to shut down.
+ * User locks are not released by transaction end, so be sure to release
+ * them explicitly.
*/
- ProcReleaseSpins(NULL);
- UnlockBuffers();
+#ifdef USER_LOCKS
+ LockReleaseAll(USER_LOCKMETHOD, true);
+#endif
+}
- /*
- * In case a transaction is open, delete any files it created. This
- * has to happen before bufmgr shutdown, so having smgr register a
- * callback for it wouldn't work.
- */
- smgrDoPendingDeletes(false);/* delete as though aborting xact */
+
+/*
+ * Returns true if at least one role is defined in this database cluster.
+ */
+static bool
+ThereIsAtLeastOneRole(void)
+{
+ Relation pg_authid_rel;
+ HeapScanDesc scan;
+ bool result;
+
+ pg_authid_rel = heap_open(AuthIdRelationId, AccessExclusiveLock);
+
+ scan = heap_beginscan(pg_authid_rel, SnapshotNow, 0, NULL);
+ result = (heap_getnext(scan, ForwardScanDirection) != NULL);
+
+ heap_endscan(scan);
+ heap_close(pg_authid_rel, AccessExclusiveLock);
+
+ return result;
}
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