postgresql/src/backend/catalog/catalog.c

/*-------------------------------------------------------------------------
 *
 * catalog.c
 *		routines concerned with catalog naming conventions and other
 *		bits of hard-wired knowledge
 *
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/catalog/catalog.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <fcntl.h>
#include <unistd.h>

#include "access/genam.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "access/transam.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_database.h"
#include "catalog/pg_db_role_setting.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_pltemplate.h"
#include "catalog/pg_replication_origin.h"
#include "catalog/pg_shdepend.h"
#include "catalog/pg_shdescription.h"
#include "catalog/pg_shseclabel.h"
#include "catalog/pg_subscription.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_type.h"
#include "catalog/toasting.h"
#include "miscadmin.h"
#include "storage/fd.h"
#include "utils/fmgroids.h"
#include "utils/fmgrprotos.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"

/*
 * IsSystemRelation
 *		True iff the relation is either a system catalog or a toast table.
 *		See IsCatalogRelation for the exact definition of a system catalog.
 *
 *		We treat toast tables of user relations as "system relations" for
 *		protection purposes, e.g. you can't change their schemas without
 *		special permissions.  Therefore, most uses of this function are
 *		checking whether allow_system_table_mods restrictions apply.
 *		For other purposes, consider whether you shouldn't be using
 *		IsCatalogRelation instead.
 *
 *		This function does not perform any catalog accesses.
 *		Some callers rely on that!
 */
bool
IsSystemRelation(Relation relation)
{
	return IsSystemClass(RelationGetRelid(relation), relation->rd_rel);
}

/*
 * IsSystemClass
 *		Like the above, but takes a Form_pg_class as argument.
 *		Used when we do not want to open the relation and have to
 *		search pg_class directly.
 */
bool
IsSystemClass(Oid relid, Form_pg_class reltuple)
{
	/* IsCatalogRelationOid is a bit faster, so test that first */
	return (IsCatalogRelationOid(relid) || IsToastClass(reltuple));
}

/*
 * IsCatalogRelation
 *		True iff the relation is a system catalog.
 *
 *		By a system catalog, we mean one that is created during the bootstrap
 *		phase of initdb.  That includes not just the catalogs per se, but
 *		also their indexes, and TOAST tables and indexes if any.
 *
 *		This function does not perform any catalog accesses.
 *		Some callers rely on that!
 */
bool
IsCatalogRelation(Relation relation)
{
	return IsCatalogRelationOid(RelationGetRelid(relation));
}

/*
 * IsCatalogRelationOid
 *		True iff the relation identified by this OID is a system catalog.
 *
 *		By a system catalog, we mean one that is created during the bootstrap
 *		phase of initdb.  That includes not just the catalogs per se, but
 *		also their indexes, and TOAST tables and indexes if any.
 *
 *		This function does not perform any catalog accesses.
 *		Some callers rely on that!
 */
bool
IsCatalogRelationOid(Oid relid)
{
	/*
	 * We consider a relation to be a system catalog if it has an OID that was
	 * manually assigned or assigned by genbki.pl.  This includes all the
	 * defined catalogs, their indexes, and their TOAST tables and indexes.
	 *
	 * This rule excludes the relations in information_schema, which are not
	 * integral to the system and can be treated the same as user relations.
	 * (Since it's valid to drop and recreate information_schema, any rule
	 * that did not act this way would be wrong.)
	 *
	 * This test is reliable since an OID wraparound will skip this range of
	 * OIDs; see GetNewObjectId().
	 */
	return (relid < (Oid) FirstBootstrapObjectId);
}

/*
 * IsToastRelation
 *		True iff relation is a TOAST support relation (or index).
 *
 *		Does not perform any catalog accesses.
 */
bool
IsToastRelation(Relation relation)
{
	/*
	 * What we actually check is whether the relation belongs to a pg_toast
	 * namespace.  This should be equivalent because of restrictions that are
	 * enforced elsewhere against creating user relations in, or moving
	 * relations into/out of, a pg_toast namespace.  Notice also that this
	 * will not say "true" for toast tables belonging to other sessions' temp
	 * tables; we expect that other mechanisms will prevent access to those.
	 */
	return IsToastNamespace(RelationGetNamespace(relation));
}

/*
 * IsToastClass
 *		Like the above, but takes a Form_pg_class as argument.
 *		Used when we do not want to open the relation and have to
 *		search pg_class directly.
 */
bool
IsToastClass(Form_pg_class reltuple)
{
	Oid			relnamespace = reltuple->relnamespace;

	return IsToastNamespace(relnamespace);
}

/*
 * IsCatalogNamespace
 *		True iff namespace is pg_catalog.
 *
 *		Does not perform any catalog accesses.
 *
 * NOTE: the reason this isn't a macro is to avoid having to include
 * catalog/pg_namespace.h in a lot of places.
 */
bool
IsCatalogNamespace(Oid namespaceId)
{
	return namespaceId == PG_CATALOG_NAMESPACE;
}

/*
 * IsToastNamespace
 *		True iff namespace is pg_toast or my temporary-toast-table namespace.
 *
 *		Does not perform any catalog accesses.
 *
 * Note: this will return false for temporary-toast-table namespaces belonging
 * to other backends.  Those are treated the same as other backends' regular
 * temp table namespaces, and access is prevented where appropriate.
 * If you need to check for those, you may be able to use isAnyTempNamespace,
 * but beware that that does involve a catalog access.
 */
bool
IsToastNamespace(Oid namespaceId)
{
	return (namespaceId == PG_TOAST_NAMESPACE) ||
		isTempToastNamespace(namespaceId);
}


/*
 * IsReservedName
 *		True iff name starts with the pg_ prefix.
 *
 *		For some classes of objects, the prefix pg_ is reserved for
 *		system objects only.  As of 8.0, this was only true for
 *		schema and tablespace names.  With 9.6, this is also true
 *		for roles.
 */
bool
IsReservedName(const char *name)
{
	/* ugly coding for speed */
	return (name[0] == 'p' &&
			name[1] == 'g' &&
			name[2] == '_');
}


/*
 * IsSharedRelation
 *		Given the OID of a relation, determine whether it's supposed to be
 *		shared across an entire database cluster.
 *
 * In older releases, this had to be hard-wired so that we could compute the
 * locktag for a relation and lock it before examining its catalog entry.
 * Since we now have MVCC catalog access, the race conditions that made that
 * a hard requirement are gone, so we could look at relaxing this restriction.
 * However, if we scanned the pg_class entry to find relisshared, and only
 * then locked the relation, pg_class could get updated in the meantime,
 * forcing us to scan the relation again, which would definitely be complex
 * and might have undesirable performance consequences.  Fortunately, the set
 * of shared relations is fairly static, so a hand-maintained list of their
 * OIDs isn't completely impractical.
 */
bool
IsSharedRelation(Oid relationId)
{
	/* These are the shared catalogs (look for BKI_SHARED_RELATION) */
	if (relationId == AuthIdRelationId ||
		relationId == AuthMemRelationId ||
		relationId == DatabaseRelationId ||
		relationId == PLTemplateRelationId ||
		relationId == SharedDescriptionRelationId ||
		relationId == SharedDependRelationId ||
		relationId == SharedSecLabelRelationId ||
		relationId == TableSpaceRelationId ||
		relationId == DbRoleSettingRelationId ||
		relationId == ReplicationOriginRelationId ||
		relationId == SubscriptionRelationId)
		return true;
	/* These are their indexes (see indexing.h) */
	if (relationId == AuthIdRolnameIndexId ||
		relationId == AuthIdOidIndexId ||
		relationId == AuthMemRoleMemIndexId ||
		relationId == AuthMemMemRoleIndexId ||
		relationId == DatabaseNameIndexId ||
		relationId == DatabaseOidIndexId ||
		relationId == PLTemplateNameIndexId ||
		relationId == SharedDescriptionObjIndexId ||
		relationId == SharedDependDependerIndexId ||
		relationId == SharedDependReferenceIndexId ||
		relationId == SharedSecLabelObjectIndexId ||
		relationId == TablespaceOidIndexId ||
		relationId == TablespaceNameIndexId ||
		relationId == DbRoleSettingDatidRolidIndexId ||
		relationId == ReplicationOriginIdentIndex ||
		relationId == ReplicationOriginNameIndex ||
		relationId == SubscriptionObjectIndexId ||
		relationId == SubscriptionNameIndexId)
		return true;
	/* These are their toast tables and toast indexes (see toasting.h) */
	if (relationId == PgAuthidToastTable ||
		relationId == PgAuthidToastIndex ||
		relationId == PgDatabaseToastTable ||
		relationId == PgDatabaseToastIndex ||
		relationId == PgDbRoleSettingToastTable ||
		relationId == PgDbRoleSettingToastIndex ||
		relationId == PgPlTemplateToastTable ||
		relationId == PgPlTemplateToastIndex ||
		relationId == PgReplicationOriginToastTable ||
		relationId == PgReplicationOriginToastIndex ||
		relationId == PgShdescriptionToastTable ||
		relationId == PgShdescriptionToastIndex ||
		relationId == PgShseclabelToastTable ||
		relationId == PgShseclabelToastIndex ||
		relationId == PgSubscriptionToastTable ||
		relationId == PgSubscriptionToastIndex ||
		relationId == PgTablespaceToastTable ||
		relationId == PgTablespaceToastIndex)
		return true;
	return false;
}


/*
 * GetNewOidWithIndex
 *		Generate a new OID that is unique within the system relation.
 *
 * Since the OID is not immediately inserted into the table, there is a
 * race condition here; but a problem could occur only if someone else
 * managed to cycle through 2^32 OIDs and generate the same OID before we
 * finish inserting our row.  This seems unlikely to be a problem.  Note
 * that if we had to *commit* the row to end the race condition, the risk
 * would be rather higher; therefore we use SnapshotAny in the test, so that
 * we will see uncommitted rows.  (We used to use SnapshotDirty, but that has
 * the disadvantage that it ignores recently-deleted rows, creating a risk
 * of transient conflicts for as long as our own MVCC snapshots think a
 * recently-deleted row is live.  The risk is far higher when selecting TOAST
 * OIDs, because SnapshotToast considers dead rows as active indefinitely.)
 *
 * Note that we are effectively assuming that the table has a relatively small
 * number of entries (much less than 2^32) and there aren't very long runs of
 * consecutive existing OIDs.  This is a mostly reasonable assumption for
 * system catalogs.
 *
 * Caller must have a suitable lock on the relation.
 */
Oid
GetNewOidWithIndex(Relation relation, Oid indexId, AttrNumber oidcolumn)
{
	Oid			newOid;
	SysScanDesc scan;
	ScanKeyData key;
	bool		collides;

	/* Only system relations are supported */
	Assert(IsSystemRelation(relation));

	/* In bootstrap mode, we don't have any indexes to use */
	if (IsBootstrapProcessingMode())
		return GetNewObjectId();

	/*
	 * We should never be asked to generate a new pg_type OID during
	 * pg_upgrade; doing so would risk collisions with the OIDs it wants to
	 * assign.  Hitting this assert means there's some path where we failed to
	 * ensure that a type OID is determined by commands in the dump script.
	 */
	Assert(!IsBinaryUpgrade || RelationGetRelid(relation) != TypeRelationId);

	/* Generate new OIDs until we find one not in the table */
	do
	{
		CHECK_FOR_INTERRUPTS();

		newOid = GetNewObjectId();

		ScanKeyInit(&key,
					oidcolumn,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(newOid));

		/* see notes above about using SnapshotAny */
		scan = systable_beginscan(relation, indexId, true,
								  SnapshotAny, 1, &key);

		collides = HeapTupleIsValid(systable_getnext(scan));

		systable_endscan(scan);
	} while (collides);

	return newOid;
}

/*
 * GetNewRelFileNode
 *		Generate a new relfilenode number that is unique within the
 *		database of the given tablespace.
 *
 * If the relfilenode will also be used as the relation's OID, pass the
 * opened pg_class catalog, and this routine will guarantee that the result
 * is also an unused OID within pg_class.  If the result is to be used only
 * as a relfilenode for an existing relation, pass NULL for pg_class.
 *
 * As with GetNewOidWithIndex(), there is some theoretical risk of a race
 * condition, but it doesn't seem worth worrying about.
 *
 * Note: we don't support using this in bootstrap mode.  All relations
 * created by bootstrap have preassigned OIDs, so there's no need.
 */
Oid
GetNewRelFileNode(Oid reltablespace, Relation pg_class, char relpersistence)
{
	RelFileNodeBackend rnode;
	char	   *rpath;
	bool		collides;
	BackendId	backend;

	/*
	 * If we ever get here during pg_upgrade, there's something wrong; all
	 * relfilenode assignments during a binary-upgrade run should be
	 * determined by commands in the dump script.
	 */
	Assert(!IsBinaryUpgrade);

	switch (relpersistence)
	{
		case RELPERSISTENCE_TEMP:
			backend = BackendIdForTempRelations();
			break;
		case RELPERSISTENCE_UNLOGGED:
		case RELPERSISTENCE_PERMANENT:
			backend = InvalidBackendId;
			break;
		default:
			elog(ERROR, "invalid relpersistence: %c", relpersistence);
			return InvalidOid;	/* placate compiler */
	}

	/* This logic should match RelationInitPhysicalAddr */
	rnode.node.spcNode = reltablespace ? reltablespace : MyDatabaseTableSpace;
	rnode.node.dbNode = (rnode.node.spcNode == GLOBALTABLESPACE_OID) ? InvalidOid : MyDatabaseId;

	/*
	 * The relpath will vary based on the backend ID, so we must initialize
	 * that properly here to make sure that any collisions based on filename
	 * are properly detected.
	 */
	rnode.backend = backend;

	do
	{
		CHECK_FOR_INTERRUPTS();

		/* Generate the OID */
		if (pg_class)
			rnode.node.relNode = GetNewOidWithIndex(pg_class, ClassOidIndexId,
													Anum_pg_class_oid);
		else
			rnode.node.relNode = GetNewObjectId();

		/* Check for existing file of same name */
		rpath = relpath(rnode, MAIN_FORKNUM);

		if (access(rpath, F_OK) == 0)
		{
			/* definite collision */
			collides = true;
		}
		else
		{
			/*
			 * Here we have a little bit of a dilemma: if errno is something
			 * other than ENOENT, should we declare a collision and loop? In
			 * practice it seems best to go ahead regardless of the errno.  If
			 * there is a colliding file we will get an smgr failure when we
			 * attempt to create the new relation file.
			 */
			collides = false;
		}

		pfree(rpath);
	} while (collides);

	return rnode.node.relNode;
}

/*
 * SQL callable interface for GetNewOidWithIndex().  Outside of initdb's
 * direct insertions into catalog tables, and recovering from corruption, this
 * should rarely be needed.
 *
 * Function is intentionally not documented in the user facing docs.
 */
Datum
pg_nextoid(PG_FUNCTION_ARGS)
{
	Oid			reloid = PG_GETARG_OID(0);
	Name		attname = PG_GETARG_NAME(1);
	Oid			idxoid = PG_GETARG_OID(2);
	Relation	rel;
	Relation	idx;
	HeapTuple	atttuple;
	Form_pg_attribute attform;
	AttrNumber	attno;
	Oid			newoid;

	/*
	 * As this function is not intended to be used during normal running, and
	 * only supports system catalogs (which require superuser permissions to
	 * modify), just checking for superuser ought to not obstruct valid
	 * usecases.
	 */
	if (!superuser())
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("must be superuser to call pg_nextoid()")));

	rel = table_open(reloid, RowExclusiveLock);
	idx = index_open(idxoid, RowExclusiveLock);

	if (!IsSystemRelation(rel))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("pg_nextoid() can only be used on system catalogs")));

	if (idx->rd_index->indrelid != RelationGetRelid(rel))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("index \"%s\" does not belong to table \"%s\"",
						RelationGetRelationName(idx),
						RelationGetRelationName(rel))));

	atttuple = SearchSysCacheAttName(reloid, NameStr(*attname));
	if (!HeapTupleIsValid(atttuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						NameStr(*attname), RelationGetRelationName(rel))));

	attform = ((Form_pg_attribute) GETSTRUCT(atttuple));
	attno = attform->attnum;

	if (attform->atttypid != OIDOID)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("column \"%s\" is not of type oid",
						NameStr(*attname))));

	if (IndexRelationGetNumberOfKeyAttributes(idx) != 1 ||
		idx->rd_index->indkey.values[0] != attno)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("index \"%s\" is not the index for column \"%s\"",
						RelationGetRelationName(idx),
						NameStr(*attname))));

	newoid = GetNewOidWithIndex(rel, idxoid, attno);

	ReleaseSysCache(atttuple);
	table_close(rel, RowExclusiveLock);
	index_close(idx, RowExclusiveLock);

	return newoid;
}