namespace.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	if (namespaceSearchPathValid && namespaceUser == roleid)
		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(AUTHOID,
								   ObjectIdGetDatum(roleid),
								   0, 0, 0);
			if (HeapTupleIsValid(tuple))
			{
				char	   *rname;

				rname = NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname);
				namespaceId = GetSysCacheOid(NAMESPACENAME,
											 CStringGetDatum(rname),
											 0, 0, 0);
				ReleaseSysCache(tuple);
				if (OidIsValid(namespaceId) &&
					!list_member_oid(oidlist, namespaceId) &&
					pg_namespace_aclcheck(namespaceId, roleid,
										  ACL_USAGE) == ACLCHECK_OK)
					oidlist = lappend_oid(oidlist, namespaceId);
			}
		}
		else
		{
			/* normal namespace reference */
			namespaceId = GetSysCacheOid(NAMESPACENAME,
										 CStringGetDatum(curname),
										 0, 0, 0);
			if (OidIsValid(namespaceId) &&
				!list_member_oid(oidlist, namespaceId) &&
				pg_namespace_aclcheck(namespaceId, roleid,
									  ACL_USAGE) == ACLCHECK_OK)
				oidlist = lappend_oid(oidlist, namespaceId);
		}
	}

	/*
	 * Remember the first member of the explicit list.
	 */
	if (oidlist == NIL)
		firstNS = InvalidOid;
	else
		firstNS = linitial_oid(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 (!list_member_oid(oidlist, PG_CATALOG_NAMESPACE))
		oidlist = lcons_oid(PG_CATALOG_NAMESPACE, oidlist);

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

	if (OidIsValid(mySpecialNamespace) &&
		!list_member_oid(oidlist, mySpecialNamespace))
		oidlist = lcons_oid(mySpecialNamespace, oidlist);

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

	/* Now safe to assign to state variable. */
	list_free(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 = roleid;

	/* Clean up. */
	pfree(rawname);
	list_free(namelist);
	list_free(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 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 (pg_database_aclcheck(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))));

	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_SUPERUSERID);
		/* 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;

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

	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 (myTempNamespaceSubID != InvalidSubTransactionId)
	{
		if (isCommit)
			on_shmem_exit(RemoveTempRelationsCallback, 0);
		else
		{
			myTempNamespace = InvalidOid;
			namespaceSearchPathValid = false;	/* need to rebuild list */
		}
		myTempNamespaceSubID = InvalidSubTransactionId;
	}

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

/*
 * 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;
			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 = NamespaceRelationId;
	object.objectId = tempNamespaceId;
	object.objectSubId = 0;

	deleteWhatDependsOn(&object, false);
}

/*
 * 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();

		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, GucSource source)
{
	char	   *rawname;
	List	   *namelist;
	ListCell   *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);
		list_free(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 (source >= PGC_S_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?
		 *
		 * When source == PGC_S_TEST, we are checking the argument of an ALTER
		 * DATABASE SET or ALTER USER SET command.	It could be that the
		 * intended use of the search path is for some other database, so we
		 * should not error out if it mentions schemas not present in the
		 * current database.  We reduce the message to NOTICE instead.
		 */
		foreach(l, namelist)
		{
			char	   *curname = (char *) lfirst(l);

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

	pfree(rawname);
	list_free(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 = list_make1_oid(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. 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.
 */
List *
fetch_search_path(bool includeImplicit)
{
	List	   *result;

	recomputeNamespacePath();

	result = list_copy(namespaceSearchPath);
	if (!includeImplicit)
	{
		while (result && linitial_oid(result) != firstExplicitNamespace)
			result = list_delete_first(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));
}