relcache.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 2,282 行 · 第 1/5 页

	 */
	relation = (Relation) palloc0(sizeof(RelationData));
	relation->rd_targblock = InvalidBlockNumber;

	/* make sure relation is marked as having no open file yet */
	relation->rd_fd = -1;

	/*
	 * initialize reference count
	 */
	RelationSetReferenceCount(relation, 1);

	/*
	 * all entries built with this routine are nailed-in-cache; none are
	 * for new or temp relations.
	 */
	relation->rd_isnailed = 1;
	relation->rd_isnew = false;
	relation->rd_istemp = false;

	/*
	 * initialize relation tuple form
	 *
	 * The data we insert here is pretty incomplete/bogus, but it'll serve to
	 * get us launched.  RelationCacheInitializePhase2() will read the
	 * real data from pg_class and replace what we've done here.
	 */
	relation->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

	namestrcpy(&relation->rd_rel->relname, relationName);
	relation->rd_rel->relnamespace = PG_CATALOG_NAMESPACE;

	/*
	 * It's important to distinguish between shared and non-shared
	 * relations, even at bootstrap time, to make sure we know where they
	 * are stored.	At present, all relations that formrdesc is used for
	 * are not shared.
	 */
	relation->rd_rel->relisshared = false;

	relation->rd_rel->relpages = 1;
	relation->rd_rel->reltuples = 1;
	relation->rd_rel->relkind = RELKIND_RELATION;
	relation->rd_rel->relhasoids = true;
	relation->rd_rel->relnatts = (int16) natts;

	/*
	 * initialize attribute tuple form
	 *
	 * Unlike the case with the relation tuple, this data had better be right
	 * because it will never be replaced.  The input values must be
	 * correctly defined by macros in src/include/catalog/ headers.
	 */
	relation->rd_att = CreateTemplateTupleDesc(natts,
										   relation->rd_rel->relhasoids);

	/*
	 * initialize tuple desc info
	 */
	has_not_null = false;
	for (i = 0; i < natts; i++)
	{
		relation->rd_att->attrs[i] = (Form_pg_attribute) palloc(ATTRIBUTE_TUPLE_SIZE);
		memcpy((char *) relation->rd_att->attrs[i],
			   (char *) &att[i],
			   ATTRIBUTE_TUPLE_SIZE);
		has_not_null |= att[i].attnotnull;
		/* make sure attcacheoff is valid */
		relation->rd_att->attrs[i]->attcacheoff = -1;
	}

	/* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
	relation->rd_att->attrs[0]->attcacheoff = 0;

	/* mark not-null status */
	if (has_not_null)
	{
		TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

		constr->has_not_null = true;
		relation->rd_att->constr = constr;
	}

	/*
	 * initialize relation id from info in att array (my, this is ugly)
	 */
	RelationGetRelid(relation) = relation->rd_att->attrs[0]->attrelid;

	/*
	 * initialize the relation's lock manager and RelFileNode information
	 */
	RelationInitLockInfo(relation);		/* see lmgr.c */

	if (relation->rd_rel->relisshared)
		relation->rd_node.tblNode = InvalidOid;
	else
		relation->rd_node.tblNode = MyDatabaseId;
	relation->rd_node.relNode =
		relation->rd_rel->relfilenode = RelationGetRelid(relation);

	/*
	 * initialize the rel-has-index flag, using hardwired knowledge
	 */
	relation->rd_rel->relhasindex = false;

	/* In bootstrap mode, we have no indexes */
	if (!IsBootstrapProcessingMode())
	{
		/* Otherwise, all the rels formrdesc is used for have indexes */
		relation->rd_rel->relhasindex = true;
	}

	/*
	 * add new reldesc to relcache
	 */
	RelationCacheInsert(relation);
}


/* ----------------------------------------------------------------
 *				 Relation Descriptor Lookup Interface
 * ----------------------------------------------------------------
 */

/*
 *		RelationIdCacheGetRelation
 *
 *		Lookup an existing reldesc by OID.
 *
 *		Only try to get the reldesc by looking in the cache,
 *		do not go to the disk if it's not present.
 *
 *		NB: relation ref count is incremented if successful.
 *		Caller should eventually decrement count.  (Usually,
 *		that happens by calling RelationClose().)
 */
Relation
RelationIdCacheGetRelation(Oid relationId)
{
	Relation	rd;

	RelationIdCacheLookup(relationId, rd);

	if (RelationIsValid(rd))
	{
		RelationIncrementReferenceCount(rd);
		/* revalidate nailed index if necessary */
		if (rd->rd_isnailed == 2)
			RelationReloadClassinfo(rd);
	}

	return rd;
}

/*
 *		RelationSysNameCacheGetRelation
 *
 *		As above, but lookup by name; only works for system catalogs.
 */
static Relation
RelationSysNameCacheGetRelation(const char *relationName)
{
	Relation	rd;
	NameData	name;

	/*
	 * make sure that the name key used for hash lookup is properly
	 * null-padded
	 */
	namestrcpy(&name, relationName);
	RelationSysNameCacheLookup(NameStr(name), rd);

	if (RelationIsValid(rd))
	{
		RelationIncrementReferenceCount(rd);
		/* revalidate nailed index if necessary */
		if (rd->rd_isnailed == 2)
			RelationReloadClassinfo(rd);
	}

	return rd;
}

/*
 *		RelationNodeCacheGetRelation
 *
 *		As above, but lookup by relfilenode.
 *
 * NOTE: this must NOT try to revalidate invalidated nailed indexes, since
 * that could cause us to return an entry with a different relfilenode than
 * the caller asked for.  Currently this is used only by the buffer manager.
 * Really the bufmgr's idea of relations should be separated out from the
 * relcache ...
 */
Relation
RelationNodeCacheGetRelation(RelFileNode rnode)
{
	Relation	rd;

	RelationNodeCacheLookup(rnode, rd);

	if (RelationIsValid(rd))
		RelationIncrementReferenceCount(rd);

	return rd;
}

/*
 *		RelationIdGetRelation
 *
 *		Lookup a reldesc by OID; make one if not already in cache.
 *
 *		NB: relation ref count is incremented, or set to 1 if new entry.
 *		Caller should eventually decrement count.  (Usually,
 *		that happens by calling RelationClose().)
 */
Relation
RelationIdGetRelation(Oid relationId)
{
	Relation	rd;
	RelationBuildDescInfo buildinfo;

	/*
	 * first try and get a reldesc from the cache
	 */
	rd = RelationIdCacheGetRelation(relationId);
	if (RelationIsValid(rd))
		return rd;

	/*
	 * no reldesc in the cache, so have RelationBuildDesc() build one and
	 * add it.
	 */
	buildinfo.infotype = INFO_RELID;
	buildinfo.i.info_id = relationId;

	rd = RelationBuildDesc(buildinfo, NULL);
	return rd;
}

/*
 *		RelationSysNameGetRelation
 *
 *		As above, but lookup by name; only works for system catalogs.
 */
Relation
RelationSysNameGetRelation(const char *relationName)
{
	Relation	rd;
	RelationBuildDescInfo buildinfo;

	/*
	 * first try and get a reldesc from the cache
	 */
	rd = RelationSysNameCacheGetRelation(relationName);
	if (RelationIsValid(rd))
		return rd;

	/*
	 * no reldesc in the cache, so have RelationBuildDesc() build one and
	 * add it.
	 */
	buildinfo.infotype = INFO_RELNAME;
	buildinfo.i.info_name = (char *) relationName;

	rd = RelationBuildDesc(buildinfo, NULL);
	return rd;
}

/* ----------------------------------------------------------------
 *				cache invalidation support routines
 * ----------------------------------------------------------------
 */

/*
 * RelationClose - close an open relation
 *
 *	Actually, we just decrement the refcount.
 *
 *	NOTE: if compiled with -DRELCACHE_FORCE_RELEASE then relcache entries
 *	will be freed as soon as their refcount goes to zero.  In combination
 *	with aset.c's CLOBBER_FREED_MEMORY option, this provides a good test
 *	to catch references to already-released relcache entries.  It slows
 *	things down quite a bit, however.
 */
void
RelationClose(Relation relation)
{
	/* Note: no locking manipulations needed */
	RelationDecrementReferenceCount(relation);

#ifdef RELCACHE_FORCE_RELEASE
	if (RelationHasReferenceCountZero(relation) &&
		!relation->rd_isnew)
		RelationClearRelation(relation, false);
#endif
}

/*
 * RelationReloadClassinfo - reload the pg_class row (only)
 *
 *	This function is used only for nailed indexes.  Since a REINDEX can
 *	change the relfilenode value for a nailed index, we have to reread
 *	the pg_class row anytime we get an SI invalidation on a nailed index
 *	(without throwing away the whole relcache entry, since we'd be unable
 *	to rebuild it).
 *
 *	We can't necessarily reread the pg_class row right away; we might be
 *	in a failed transaction when we receive the SI notification.  If so,
 *	RelationClearRelation just marks the entry as invalid by setting
 *	rd_isnailed to 2.  This routine is called to fix the entry when it
 *	is next needed.
 */
static void
RelationReloadClassinfo(Relation relation)
{
	RelationBuildDescInfo buildinfo;
	bool		indexOK;
	HeapTuple	pg_class_tuple;
	Form_pg_class relp;

	/* Should be called only for invalidated nailed indexes */
	Assert(relation->rd_isnailed == 2 &&
		   relation->rd_rel->relkind == RELKIND_INDEX);
	/* Read the pg_class row */
	buildinfo.infotype = INFO_RELID;
	buildinfo.i.info_id = relation->rd_id;
	/*
	 * Don't try to use an indexscan of pg_class_oid_index to reload the
	 * info for pg_class_oid_index ...
	 */
	indexOK = strcmp(RelationGetRelationName(relation), ClassOidIndex) != 0;
	pg_class_tuple = ScanPgRelation(buildinfo, indexOK);
	if (!HeapTupleIsValid(pg_class_tuple))
		elog(ERROR, "could not find tuple for system relation %u",
			 relation->rd_id);
	relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
	if (relation->rd_node.relNode != relp->relfilenode)
	{
		/* We have to re-insert the entry into the relcache indexes */
		RelationCacheDelete(relation);
		memcpy((char *) relation->rd_rel, (char *) relp, CLASS_TUPLE_SIZE);
		relation->rd_node.relNode = relp->relfilenode;
		RelationCacheInsert(relation);
	}
	heap_freetuple(pg_class_tuple);
	/* Must adjust number of blocks after we know the new relfilenode */
	relation->rd_targblock = InvalidBlockNumber;
	RelationUpdateNumberOfBlocks(relation);
	/* Okay, now it's valid again */
	relation->rd_isnailed = 1;
}

/*
 * RelationClearRelation
 *
 *	 Physically blow away a relation cache entry, or reset it and rebuild
 *	 it from scratch (that is, from catalog entries).  The latter path is
 *	 usually used when we are notified of a change to an open relation
 *	 (one with refcount > 0).  However, this routine just does whichever
 *	 it's told to do; callers must determine which they want.
 */
static void
RelationClearRelation(Relation relation, bool rebuild)
{
	MemoryContext oldcxt;

	/*
	 * Make sure smgr and lower levels close the relation's files, if they
	 * weren't closed already.  If the relation is not getting deleted,
	 * the next smgr access should reopen the files automatically.	This
	 * ensures that the low-level file access state is updated after, say,
	 * a vacuum truncation.
	 */
	if (relation->rd_fd >= 0)
	{
		smgrclose(DEFAULT_SMGR, relation);
		relation->rd_fd = -1;
	}

	/*
	 * Never, never ever blow away a nailed-in system relation, because
	 * we'd be unable to recover.  However, we must update rd_nblocks and
	 * reset rd_targblock, in case we got called because of a relation
	 * cache flush that was triggered by VACUUM.  If it's a nailed index,
	 * then we need to re-read the pg_class row to see if its relfilenode
	 * changed.  We can't necessarily do that here, because we might be in
	 * a failed transaction.  We assume it's okay to do it if there are open
	 * references to the relcache entry (cf notes for AtEOXact_RelationCache).
	 * Otherwise just mark the entry as possibly invalid, and it'll be fixed
	 * when next opened.
	 */
	if (relation->rd_isnailed)
	{
		if (relation->rd_rel->relkind == RELKIND_INDEX)
		{
			relation->rd_isnailed = 2;	/* needs to be revalidated */
			if (relation->rd_refcnt > 1)
				RelationReloadClassinfo(relation);
		}
		else
		{
			relation->rd_targblock = InvalidBlockNumber;
			RelationUpdateNumberOfBlocks(relation);
		}
		return;
	}

	/*
	 * Remove relation from hash tables
	 *
	 * Note: we might be reinserting it momentarily, but we must not have it
	 * visible in the hash tables until it's valid again, so don't try to
	 * optimize this away...
	 */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
	RelationCacheDelete(relation);
	MemoryContextSwitchTo(oldcxt);

	/* Clear out catcache's entries for this relation */
	CatalogCacheFlushRelation(RelationGetRelid(relation));

	/*
	 * Free all the subsidiary data structures of the relcache entry. We
	 * cannot free rd_att if we are trying to rebuild the entry, however,
	 * because pointers to it may be cached in various places. The rule
	 * manager might also have pointers into the rewrite rules. So to
	 * begin with, we can only get rid of these fields:
	 */
	FreeTriggerDesc(relation->trigdesc);
	if (relation->rd_indextuple)
		pfree(relation->rd_indextuple);
	if (relation->rd_am)
		pfree(relation->rd_am);
	if (relation->rd_rel)
		pfree(relation->rd_rel);
	freeList(relation->rd_indexlist);
	if (relation->rd_indexcxt)
		MemoryContextDelete(relation->rd_indexcxt);

	/*
	 * If we're really done with the relcache entry, blow it away. But if
	 * someone is still using it, reconstruct the whole deal without
	 * moving the physical RelationData record (so that the someone's
	 * pointer is still valid).
	 */
	if (!rebuild)
	{
		/* ok to zap remaining substructure */
		FreeTupleDesc(relation->rd_att);
		if (relation->rd_rulescxt)
			MemoryContextDelete(relation->rd_rulescxt);
		pfree(relation);
	}
	else
	{
		/*