namespace.c

PostgreSQL7.4.6 for Linux

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

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

/*
 * recomputeNamespacePath - recompute path derived variables if needed.
 */
static void
recomputeNamespacePath(void)
{
	AclId		userId = GetUserId();
	char	   *rawname;
	List	   *namelist;
	List	   *oidlist;
	List	   *newpath;
	List	   *l;
	Oid			firstNS;
	MemoryContext oldcxt;

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

	/* Need a modifiable copy of namespace_search_path string */
	rawname = pstrdup(namespace_search_path);

	/* 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;
	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 = SearchSysCache(SHADOWSYSID,
								   ObjectIdGetDatum(userId),
								   0, 0, 0);
			if (HeapTupleIsValid(tuple))
			{
				char	   *uname;

				uname = NameStr(((Form_pg_shadow) GETSTRUCT(tuple))->usename);
				namespaceId = GetSysCacheOid(NAMESPACENAME,
											 CStringGetDatum(uname),
											 0, 0, 0);
				ReleaseSysCache(tuple);
				if (OidIsValid(namespaceId) &&
					!oidMember(namespaceId, oidlist) &&
					pg_namespace_aclcheck(namespaceId, userId,
										  ACL_USAGE) == ACLCHECK_OK)
					oidlist = lappendo(oidlist, namespaceId);
			}
		}
		else
		{
			/* normal namespace reference */
			namespaceId = GetSysCacheOid(NAMESPACENAME,
										 CStringGetDatum(curname),
										 0, 0, 0);
			if (OidIsValid(namespaceId) &&
				!oidMember(namespaceId, oidlist) &&
				pg_namespace_aclcheck(namespaceId, userId,
									  ACL_USAGE) == ACLCHECK_OK)
				oidlist = lappendo(oidlist, namespaceId);
		}
	}

	/*
	 * Remember the first member of the explicit list.
	 */
	if (oidlist == NIL)
		firstNS = InvalidOid;
	else
		firstNS = lfirsto(oidlist);

	/*
	 * 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 (!oidMember(PG_CATALOG_NAMESPACE, oidlist))
		oidlist = lconso(PG_CATALOG_NAMESPACE, oidlist);

	if (OidIsValid(myTempNamespace) &&
		!oidMember(myTempNamespace, oidlist))
		oidlist = lconso(myTempNamespace, oidlist);

	if (OidIsValid(mySpecialNamespace) &&
		!oidMember(mySpecialNamespace, oidlist))
		oidlist = lconso(mySpecialNamespace, oidlist);

	/*
	 * Now that we've successfully built the new list of namespace OIDs,
	 * save it in permanent storage.
	 */
	oldcxt = MemoryContextSwitchTo(TopMemoryContext);
	newpath = listCopy(oidlist);
	MemoryContextSwitchTo(oldcxt);

	/* Now safe to assign to state variable. */
	freeList(namespaceSearchPath);
	namespaceSearchPath = newpath;

	/*
	 * Update info derived from search path.
	 */
	firstExplicitNamespace = firstNS;
	if (OidIsValid(mySpecialNamespace))
		defaultCreationNamespace = mySpecialNamespace;
	else
		defaultCreationNamespace = firstNS;

	/* Mark the path valid. */
	namespaceSearchPathValid = true;
	namespaceUser = userId;

	/* Clean up. */
	pfree(rawname);
	freeList(namelist);
	freeList(oidlist);
}

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

	/*
	 * 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 we apply the check to the session user, not the currently active
	 * userid, since we are not going to change our minds about temp table
	 * availability during the session.
	 */
	if (pg_database_aclcheck(MyDatabaseId, GetSessionUserId(),
							 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))));

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

	namespaceId = GetSysCacheOid(NAMESPACENAME,
								 CStringGetDatum(namespaceName),
								 0, 0, 0);
	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_USESYSID);
		/* 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);
	}

	/*
	 * 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;

	firstTempTransaction = true;

	namespaceSearchPathValid = false;	/* need to rebuild list */
}

/*
 * End-of-transaction cleanup for namespaces.
 */
void
AtEOXact_Namespace(bool isCommit)
{
	/*
	 * 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 (firstTempTransaction)
	{
		if (isCommit)
			on_shmem_exit(RemoveTempRelationsCallback, 0);
		else
		{
			myTempNamespace = InvalidOid;
			namespaceSearchPathValid = false;	/* need to rebuild list */
		}
		firstTempTransaction = false;
	}

	/*
	 * Clean up if someone failed to do PopSpecialNamespace
	 */
	if (OidIsValid(mySpecialNamespace))
	{
		mySpecialNamespace = InvalidOid;
		namespaceSearchPathValid = false;		/* need to rebuild list */
	}
}

/*
 * 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).  We do this by finding everything that has a
	 * dependency on the namespace.
	 */
	object.classId = get_system_catalog_relid(NamespaceRelationName);
	object.objectId = tempNamespaceId;
	object.objectSubId = 0;

	deleteWhatDependsOn(&object, false);
}

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

		RemoveTempRelations(myTempNamespace);

		CommitTransactionCommand();
	}
}


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

/* assign_hook: validate new search_path, do extra actions as needed */
const char *
assign_search_path(const char *newval, bool doit, bool interactive)
{
	char	   *rawname;
	List	   *namelist;
	List	   *l;

	/* Need a modifiable copy of string */
	rawname = pstrdup(newval);

	/* Parse string into list of identifiers */
	if (!SplitIdentifierString(rawname, ',', &namelist))
	{
		/* syntax error in name list */
		pfree(rawname);
		freeList(namelist);
		return NULL;
	}

	/*
	 * If we aren't inside a transaction, we cannot do database access so
	 * cannot verify the individual names.	Must accept the list on faith.
	 */
	if (interactive && IsTransactionState())
	{
		/*
		 * Verify that all the names are either valid namespace names or
		 * "$user".  We do not require $user to correspond to a valid
		 * namespace.  We do not check for USAGE rights, either; should
		 * we?
		 */
		foreach(l, namelist)
		{
			char	   *curname = (char *) lfirst(l);

			if (strcmp(curname, "$user") == 0)
				continue;
			if (!SearchSysCacheExists(NAMESPACENAME,
									  CStringGetDatum(curname),
									  0, 0, 0))
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_SCHEMA),
					   errmsg("schema \"%s\" does not exist", curname)));
		}
	}

	pfree(rawname);
	freeList(namelist);

	/*
	 * 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.
	 */
	if (doit)
		namespaceSearchPathValid = false;

	return newval;
}

/*
 * 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);
		namespaceSearchPath = makeListo1(PG_CATALOG_NAMESPACE);
		MemoryContextSwitchTo(oldcxt);
		defaultCreationNamespace = PG_CATALOG_NAMESPACE;
		firstExplicitNamespace = PG_CATALOG_NAMESPACE;
		namespaceSearchPathValid = true;
		namespaceUser = GetUserId();
	}
	else
	{
		/*
		 * In normal mode, arrange for a callback on any syscache
		 * invalidation of pg_namespace rows.
		 */
		CacheRegisterSyscacheCallback(NAMESPACEOID,
									  NamespaceCallback,
									  (Datum) 0);
		/* Force search path to be recomputed on next use */
		namespaceSearchPathValid = false;
	}
}

/*
 * NamespaceCallback
 *		Syscache inval callback function
 */
static void
NamespaceCallback(Datum arg, Oid relid)
{
	/* Force search path to be recomputed on next use */
	namespaceSearchPathValid = false;
}

/*
 * Fetch the active search path, expressed as a List of OIDs.
 *
 * The returned list includes the implicitly-prepended namespaces only if
 * includeImplicit is true.
 *
 * NB: caller must treat the list as read-only!
 */
List *
fetch_search_path(bool includeImplicit)
{
	List	   *result;

	recomputeNamespacePath();

	result = namespaceSearchPath;
	if (!includeImplicit)
	{
		while (result && lfirsto(result) != firstExplicitNamespace)
			result = lnext(result);
	}

	return result;
}

/*
 * Export the FooIsVisible functions as SQL-callable functions.
 */

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

	PG_RETURN_BOOL(RelationIsVisible(oid));
}

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

	PG_RETURN_BOOL(TypeIsVisible(oid));
}

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

	PG_RETURN_BOOL(FunctionIsVisible(oid));
}

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

	PG_RETURN_BOOL(OperatorIsVisible(oid));
}

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

	PG_RETURN_BOOL(OpclassIsVisible(oid));
}

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

	PG_RETURN_BOOL(ConversionIsVisible(oid));
}