postinit.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	DebugFileOpen();

	/* Do local initialization of file, storage and buffer managers */
	InitFileAccess();
	smgrinit();
	InitBufferPoolAccess();
}


/* --------------------------------
 * 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.
 * --------------------------------
 */
bool
InitPostgres(const char *dbname, const char *username)
{
	bool		bootstrap = IsBootstrapProcessingMode();
	bool		autovacuum = IsAutoVacuumProcess();
	bool		am_superuser;

	/*
	 * 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;
		MyDatabaseTableSpace = DEFAULTTABLESPACE_OID;
		SetDatabasePath(GetDatabasePath(MyDatabaseId, MyDatabaseTableSpace));
	}
	else
	{
		char	   *fullpath;

		/*
		 * Formerly we validated DataDir here, but now that's done earlier.
		 */

		/*
		 * 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
		 * FindMyDatabase.
		 */
		if (!FindMyDatabase(dbname, &MyDatabaseId, &MyDatabaseTableSpace))
			ereport(FATAL,
					(errcode(ERRCODE_UNDEFINED_DATABASE),
					 errmsg("database \"%s\" does not exist",
							dbname)));

		fullpath = GetDatabasePath(MyDatabaseId, MyDatabaseTableSpace);

		/* Verify the database path */

		if (access(fullpath, F_OK) == -1)
		{
			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);

		SetDatabasePath(fullpath);
	}

	/*
	 * Code after this point assumes we are in the proper directory!
	 */

	/*
	 * 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!
	 *
	 * Sets up MyBackendId, a unique backend identifier.
	 */
	MyBackendId = InvalidBackendId;

	InitBackendSharedInvalidationState();

	if (MyBackendId > MaxBackends || MyBackendId <= 0)
		elog(FATAL, "bad backend id: %d", MyBackendId);

	/*
	 * bufmgr needs another initialization call too
	 */
	InitBufferPoolBackend();

	/*
	 * 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();

	/*
	 * 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.
	 */
	on_shmem_exit(ShutdownPostgres, 0);

	/* start a new transaction here before access to db */
	if (!bootstrap)
		StartTransactionCommand();

	/*
	 * It's now possible to do real access to the system catalogs.
	 *
	 * Replace faked-up relcache entries with correct info.
	 */
	RelationCacheInitializePhase2();

	/*
	 * 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 || 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
	{
		/* 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.  (Also, it wants to know if the user is a
	 * superuser, so the above stuff has to happen first.)
	 */
	if (!bootstrap)
		ReverifyMyDatabase(dbname);

	/*
	 * 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();

	/*
	 * Check if user is a superuser.
	 */
	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")));

	/*
	 * Initialize various default states that can't be set up until we've
	 * selected the active user and done ReverifyMyDatabase.
	 */

	/* 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.
 *
 * User-level cleanup, such as temp-relation removal and UNLISTEN, happens
 * via separate callbacks that execute before this one.  We don't combine the
 * callbacks because we still want this one to happen if the user-level
 * cleanup fails.
 */
static void
ShutdownPostgres(int code, Datum arg)
{
	/* Make sure we've killed any active transaction */
	AbortOutOfAnyTransaction();

	/*
	 * User locks are not released by transaction end, so be sure to release
	 * them explicitly.
	 */
#ifdef USER_LOCKS
	LockReleaseAll(USER_LOCKMETHOD, true);
#endif
}


/*
 * 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;
}