namespace.c

PostgreSQL7.4.6 for Linux

/*-------------------------------------------------------------------------
 *
 * 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) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.58 2003/09/25 06:57:57 petere Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/xact.h"
#include "catalog/catname.h"
#include "catalog/dependency.h"
#include "catalog/namespace.h"
#include "catalog/pg_conversion.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_shadow.h"
#include "catalog/pg_type.h"
#include "commands/dbcommands.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "storage/backendid.h"
#include "storage/ipc.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/syscache.h"


/*
 * The namespace search path is a possibly-empty list of namespace OIDs.
 * In addition to the explicit list, several implicitly-searched namespaces
 * may be included:
 *
 * 1. If a "special" namespace has been set by PushSpecialNamespace, it is
 * always searched first.  (This is a hack for CREATE SCHEMA.)
 *
 * 2. If a TEMP table namespace has been initialized in this session, it
 * is always searched just after any special namespace.
 *
 * 3. 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.)
 *
 * The default creation target namespace is normally equal to the first
 * element of the explicit list, but is the "special" namespace when one
 * has been set.  If the explicit list is empty and there is no special
 * namespace, there is no default target.
 *
 * 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.
 * The initdb script 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).
 *
 * If namespaceSearchPathValid is false, then namespaceSearchPath (and other
 * derived variables) need to be recomputed from namespace_search_path.
 * We mark it invalid upon an assignment to namespace_search_path or receipt
 * of a syscache invalidation event for pg_namespace.  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 namespaceSearchPath; so
 * we have to be willing to recompute the path when current userid changes.
 * namespaceUser is the userid the path has been computed for.
 */

static List *namespaceSearchPath = NIL;

static Oid	namespaceUser = InvalidOid;

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

/* first explicit member of list; usually same as defaultCreationNamespace */
static Oid	firstExplicitNamespace = InvalidOid;

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

/*
 * 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.
 * firstTempTransaction flags whether we've committed creation of the TEMP
 * namespace or not.
 */
static Oid	myTempNamespace = InvalidOid;

static bool firstTempTransaction = false;

/*
 * "Special" namespace for CREATE SCHEMA.  If set, it's the first search
 * path element, and also the default creation namespace.
 */
static Oid	mySpecialNamespace = InvalidOid;

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


/* Local functions */
static void recomputeNamespacePath(void);
static void InitTempTableNamespace(void);
static void RemoveTempRelations(Oid tempNamespaceId);
static void RemoveTempRelationsCallback(void);
static void NamespaceCallback(Datum arg, Oid relid);

/* These don't really need to appear in any header file */
Datum		pg_table_is_visible(PG_FUNCTION_ARGS);
Datum		pg_type_is_visible(PG_FUNCTION_ARGS);
Datum		pg_function_is_visible(PG_FUNCTION_ARGS);
Datum		pg_operator_is_visible(PG_FUNCTION_ARGS);
Datum		pg_opclass_is_visible(PG_FUNCTION_ARGS);
Datum		pg_conversion_is_visible(PG_FUNCTION_ARGS);


/*
 * RangeVarGetRelid
 *		Given a RangeVar describing an existing relation,
 *		select the proper namespace and look up the relation OID.
 *
 * If the relation is not found, return InvalidOid if failOK = true,
 * otherwise raise an error.
 */
Oid
RangeVarGetRelid(const RangeVar *relation, bool failOK)
{
	Oid			namespaceId;
	Oid			relId;

	/*
	 * 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")));
	}

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

	if (!OidIsValid(relId) && !failOK)
	{
		if (relation->schemaname)
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_TABLE),
					 errmsg("relation \"%s.%s\" does not exist",
							relation->schemaname, relation->relname)));
		else
			ereport(ERROR,
					(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")));
	}

	if (newRelation->istemp)
	{
		/* TEMP tables are created in our backend-local temp namespace */
		if (newRelation->schemaname)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				   errmsg("temporary tables may not specify a schema name")));
		/* Initialize temp namespace if first time through */
		if (!OidIsValid(myTempNamespace))
			InitTempTableNamespace();
		return myTempNamespace;
	}

	if (newRelation->schemaname)
	{
		/* use exact schema given */
		namespaceId = GetSysCacheOid(NAMESPACENAME,
								CStringGetDatum(newRelation->schemaname),
									 0, 0, 0);
		if (!OidIsValid(namespaceId))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_SCHEMA),
					 errmsg("schema \"%s\" does not exist",
							newRelation->schemaname)));
		/* we do not check for USAGE rights here! */
	}
	else
	{
		/* use the default creation namespace */
		recomputeNamespacePath();
		namespaceId = defaultCreationNamespace;
		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;
}

/*
 * 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;
	List	   *lptr;

	recomputeNamespacePath();

	foreach(lptr, namespaceSearchPath)
	{
		Oid			namespaceId = lfirsto(lptr);

		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)
{
	HeapTuple	reltup;
	Form_pg_class relform;
	Oid			relnamespace;
	bool		visible;

	reltup = SearchSysCache(RELOID,
							ObjectIdGetDatum(relid),
							0, 0, 0);
	if (!HeapTupleIsValid(reltup))
		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 oidMember() for them.
	 */
	relnamespace = relform->relnamespace;
	if (relnamespace != PG_CATALOG_NAMESPACE &&
		!oidMember(relnamespace, namespaceSearchPath))
		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 to see if this rel would be
		 * found by RelnameGetRelid.
		 */
		char	   *relname = NameStr(relform->relname);

		visible = (RelnameGetRelid(relname) == relid);
	}

	ReleaseSysCache(reltup);

	return visible;
}


/*
 * TypenameGetTypid
 *		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
TypenameGetTypid(const char *typname)
{
	Oid			typid;
	List	   *lptr;

	recomputeNamespacePath();

	foreach(lptr, namespaceSearchPath)
	{
		Oid			namespaceId = lfirsto(lptr);

		typid = GetSysCacheOid(TYPENAMENSP,
							   PointerGetDatum(typname),
							   ObjectIdGetDatum(namespaceId),
							   0, 0);
		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)
{
	HeapTuple	typtup;
	Form_pg_type typform;
	Oid			typnamespace;
	bool		visible;

	typtup = SearchSysCache(TYPEOID,
							ObjectIdGetDatum(typid),
							0, 0, 0);
	if (!HeapTupleIsValid(typtup))
		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 oidMember() for them.
	 */
	typnamespace = typform->typnamespace;
	if (typnamespace != PG_CATALOG_NAMESPACE &&
		!oidMember(typnamespace, namespaceSearchPath))
		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 to see if this type would be found
		 * by TypenameGetTypid.
		 */
		char	   *typname = NameStr(typform->typname);

		visible = (TypenameGetTypid(typname) == typid);
	}

	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.
 *
 * We search a single namespace if the function 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.
 */
FuncCandidateList
FuncnameGetCandidates(List *names, int nargs)
{
	FuncCandidateList resultList = NULL;
	char	   *schemaname;
	char	   *funcname;
	Oid			namespaceId;
	CatCList   *catlist;
	int			i;

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

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

	/* Search syscache by name and (optionally) nargs only */
	if (nargs >= 0)
		catlist = SearchSysCacheList(PROCNAMENSP, 2,
									 CStringGetDatum(funcname),
									 Int16GetDatum(nargs),
									 0, 0);
	else
		catlist = SearchSysCacheList(PROCNAMENSP, 1,
									 CStringGetDatum(funcname),
									 0, 0, 0);

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

		nargs = procform->pronargs;

		if (OidIsValid(namespaceId))
		{
			/* Consider only procs in specified namespace */