uqa-pg-query 0.1.6

/*--------------------------------------------------------------------
 * Symbols referenced in this file:
 * - IsCatalogRelationOid
 * - IsCatalogNamespace
 *--------------------------------------------------------------------
 */

/*-------------------------------------------------------------------------
 *
 * catalog.c
 *		routines concerned with catalog naming conventions and other
 *		bits of hard-wired knowledge
 *
 *
 * Portions Copyright (c) 1996-2025, 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/table.h"
#include "access/transam.h"
#include "catalog/catalog.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_largeobject.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_parameter_acl.h"
#include "catalog/pg_replication_origin.h"
#include "catalog/pg_seclabel.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 "miscadmin.h"
#include "utils/fmgroids.h"
#include "utils/fmgrprotos.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"

/*
 * Parameters to determine when to emit a log message in
 * GetNewOidWithIndex()
 */
#define GETNEWOID_LOG_THRESHOLD 1000000
#define GETNEWOID_LOG_MAX_INTERVAL 128000000

/*
 * 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!
 */


/*
 * 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.
 */


/*
 * 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!
 */


/*
 * 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 a pinned OID.
	 * 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) FirstUnpinnedObjectId);
}

/*
 * IsCatalogTextUniqueIndexOid
 *		True iff the relation identified by this OID is a catalog UNIQUE index
 *		having a column of type "text".
 *
 *		The relcache must not use these indexes.  Inserting into any UNIQUE
 *		index compares index keys while holding BUFFER_LOCK_EXCLUSIVE.
 *		bttextcmp() can search the COLLOID catcache.  Depending on concurrent
 *		invalidation traffic, catcache can reach relcache builds.  A backend
 *		would self-deadlock on LWLocks if the relcache build read the
 *		exclusive-locked buffer.
 *
 *		To avoid being itself the cause of self-deadlock, this doesn't read
 *		catalogs.  Instead, it uses a hard-coded list with a supporting
 *		regression test.
 */


/*
 * IsInplaceUpdateRelation
 *		True iff core code performs inplace updates on the relation.
 *
 *		This is used for assertions and for making the executor follow the
 *		locking protocol described at README.tuplock section "Locking to write
 *		inplace-updated tables".  Extensions may inplace-update other heap
 *		tables, but concurrent SQL UPDATE on the same table may overwrite
 *		those modifications.
 *
 *		The executor can assume these are not partitions or partitioned and
 *		have no triggers.
 */


/*
 * IsInplaceUpdateOid
 *		Like the above, but takes an OID as argument.
 */


/*
 * IsToastRelation
 *		True iff relation is a TOAST support relation (or index).
 *
 *		Does not perform any catalog accesses.
 */


/*
 * 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.
 */


/*
 * 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.
 */



/*
 * 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.
 */



/*
 * 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.
 */


/*
 * IsPinnedObject
 *		Given the class + OID identity of a database object, report whether
 *		it is "pinned", that is not droppable because the system requires it.
 *
 * We used to represent this explicitly in pg_depend, but that proved to be
 * an undesirable amount of overhead, so now we rely on an OID range test.
 */



/*
 * 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.
 */


/*
 * GetNewRelFileNumber
 *		Generate a new relfilenumber that is unique within the
 *		database of the given tablespace.
 *
 * If the relfilenumber 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 relfilenumber 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.
 */


/*
 * 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.
 */


/*
 * SQL callable interface for StopGeneratingPinnedObjectIds().
 *
 * This is only to be used by initdb, so it's intentionally not documented in
 * the user facing docs.
 */