relcache.c

来自「postgresql8.3.4源码,开源数据库」· C语言 代码 · 共 2,134 行 · 第 1/5 页

		while (HeapTupleIsValid(htup = systable_getnext(scan)))
		{
			Form_pg_amop amopform = (Form_pg_amop) GETSTRUCT(htup);

			if (amopform->amopstrategy <= 0 ||
				(StrategyNumber) amopform->amopstrategy > numStrats)
				elog(ERROR, "invalid amopstrategy number %d for opclass %u",
					 amopform->amopstrategy, operatorClassOid);
			opcentry->operatorOids[amopform->amopstrategy - 1] =
				amopform->amopopr;
		}

		systable_endscan(scan);
		heap_close(rel, AccessShareLock);
	}

	/*
	 * Scan pg_amproc to obtain support procs for the opclass.	We only fetch
	 * the default ones (those with lefttype = righttype = opcintype).
	 */
	if (numSupport > 0)
	{
		ScanKeyInit(&skey[0],
					Anum_pg_amproc_amprocfamily,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcfamily));
		ScanKeyInit(&skey[1],
					Anum_pg_amproc_amproclefttype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcintype));
		ScanKeyInit(&skey[2],
					Anum_pg_amproc_amprocrighttype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcintype));
		rel = heap_open(AccessMethodProcedureRelationId, AccessShareLock);
		scan = systable_beginscan(rel, AccessMethodProcedureIndexId, indexOK,
								  SnapshotNow, 3, skey);

		while (HeapTupleIsValid(htup = systable_getnext(scan)))
		{
			Form_pg_amproc amprocform = (Form_pg_amproc) GETSTRUCT(htup);

			if (amprocform->amprocnum <= 0 ||
				(StrategyNumber) amprocform->amprocnum > numSupport)
				elog(ERROR, "invalid amproc number %d for opclass %u",
					 amprocform->amprocnum, operatorClassOid);

			opcentry->supportProcs[amprocform->amprocnum - 1] =
				amprocform->amproc;
		}

		systable_endscan(scan);
		heap_close(rel, AccessShareLock);
	}

	opcentry->valid = true;
	return opcentry;
}


/*
 *		formrdesc
 *
 *		This is a special cut-down version of RelationBuildDesc()
 *		used by RelationCacheInitializePhase2() in initializing the relcache.
 *		The relation descriptor is built just from the supplied parameters,
 *		without actually looking at any system table entries.  We cheat
 *		quite a lot since we only need to work for a few basic system
 *		catalogs.
 *
 * formrdesc is currently used for: pg_class, pg_attribute, pg_proc,
 * and pg_type (see RelationCacheInitializePhase2).
 *
 * Note that these catalogs can't have constraints (except attnotnull),
 * default values, rules, or triggers, since we don't cope with any of that.
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static void
formrdesc(const char *relationName, Oid relationReltype,
		  bool hasoids, int natts, FormData_pg_attribute *att)
{
	Relation	relation;
	int			i;
	bool		has_not_null;

	/*
	 * allocate new relation desc, clear all fields of reldesc
	 */
	relation = (Relation) palloc0(sizeof(RelationData));
	relation->rd_targblock = InvalidBlockNumber;

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

	/*
	 * initialize reference count: 1 because it is nailed in cache
	 */
	relation->rd_refcnt = 1;

	/*
	 * all entries built with this routine are nailed-in-cache; none are for
	 * new or temp relations.
	 */
	relation->rd_isnailed = true;
	relation->rd_createSubid = InvalidSubTransactionId;
	relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
	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;
	relation->rd_rel->reltype = relationReltype;

	/*
	 * 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 = hasoids;
	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, hasoids);
	relation->rd_att->tdrefcount = 1;	/* mark as refcounted */

	relation->rd_att->tdtypeid = relationReltype;
	relation->rd_att->tdtypmod = -1;	/* unnecessary, but... */

	/*
	 * initialize tuple desc info
	 */
	has_not_null = false;
	for (i = 0; i < natts; i++)
	{
		memcpy(relation->rd_att->attrs[i],
			   &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;
	relation->rd_rel->relfilenode = RelationGetRelid(relation);

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

	/*
	 * initialize physical addressing information for the relation
	 */
	RelationInitPhysicalAddr(relation);

	/*
	 * initialize the rel-has-index flag, using hardwired knowledge
	 */
	if (IsBootstrapProcessingMode())
	{
		/* In bootstrap mode, we have no indexes */
		relation->rd_rel->relhasindex = false;
	}
	else
	{
		/* Otherwise, all the rels formrdesc is used for have indexes */
		relation->rd_rel->relhasindex = true;
	}

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

	/* It's fully valid */
	relation->rd_isvalid = true;
}


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

/*
 *		RelationIdGetRelation
 *
 *		Lookup a reldesc by OID; make one if not already in cache.
 *
 *		Returns NULL if no pg_class row could be found for the given relid
 *		(suggesting we are trying to access a just-deleted relation).
 *		Any other error is reported via elog.
 *
 *		NB: caller should already have at least AccessShareLock on the
 *		relation ID, else there are nasty race conditions.
 *
 *		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;

	/*
	 * first try to find reldesc in the cache
	 */
	RelationIdCacheLookup(relationId, rd);

	if (RelationIsValid(rd))
	{
		RelationIncrementReferenceCount(rd);
		/* revalidate nailed index if necessary */
		if (!rd->rd_isvalid)
			RelationReloadIndexInfo(rd);
		return rd;
	}

	/*
	 * no reldesc in the cache, so have RelationBuildDesc() build one and add
	 * it.
	 */
	rd = RelationBuildDesc(relationId, NULL);
	if (RelationIsValid(rd))
		RelationIncrementReferenceCount(rd);
	return rd;
}

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

/*
 * RelationIncrementReferenceCount
 *		Increments relation reference count.
 *
 * Note: bootstrap mode has its own weird ideas about relation refcount
 * behavior; we ought to fix it someday, but for now, just disable
 * reference count ownership tracking in bootstrap mode.
 */
void
RelationIncrementReferenceCount(Relation rel)
{
	ResourceOwnerEnlargeRelationRefs(CurrentResourceOwner);
	rel->rd_refcnt += 1;
	if (!IsBootstrapProcessingMode())
		ResourceOwnerRememberRelationRef(CurrentResourceOwner, rel);
}

/*
 * RelationDecrementReferenceCount
 *		Decrements relation reference count.
 */
void
RelationDecrementReferenceCount(Relation rel)
{
	Assert(rel->rd_refcnt > 0);
	rel->rd_refcnt -= 1;
	if (!IsBootstrapProcessingMode())
		ResourceOwnerForgetRelationRef(CurrentResourceOwner, rel);
}

/*
 * 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_createSubid == InvalidSubTransactionId &&
		relation->rd_newRelfilenodeSubid == InvalidSubTransactionId)
		RelationClearRelation(relation, false);
#endif
}

/*
 * RelationReloadIndexInfo - reload minimal information for an open index
 *
 *	This function is used only for indexes.  A relcache inval on an index
 *	can mean that its pg_class or pg_index row changed.  There are only
 *	very limited changes that are allowed to an existing index's schema,
 *	so we can update the relcache entry without a complete rebuild; which
 *	is fortunate because we can't rebuild an index entry that is "nailed"
 *	and/or in active use.  We support full replacement of the pg_class row,
 *	as well as updates of a few simple fields of the pg_index row.
 *
 *	We can't necessarily reread the catalog rows 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_isvalid to false.  This routine is called to fix the entry when it
 *	is next needed.
 *
 *	We assume that at the time we are called, we have at least AccessShareLock
 *	on the target index.  (Note: in the calls from RelationClearRelation,
 *	this is legitimate because we know the rel has positive refcount.)
 */
static void
RelationReloadIndexInfo(Relation relation)
{
	bool		indexOK;
	HeapTuple	pg_class_tuple;
	Form_pg_class relp;

	/* Should be called only for invalidated indexes */
	Assert(relation->rd_rel->relkind == RELKIND_INDEX &&
		   !relation->rd_isvalid);
	/* Should be closed at smgr level */
	Assert(relation->rd_smgr == NULL);

	/*
	 * Read the pg_class row
	 *
	 * Don't try to use an indexscan of pg_class_oid_index to reload the info
	 * for pg_class_oid_index ...
	 */
	indexOK = (RelationGetRelid(relation) != ClassOidIndexId);
	pg_class_tuple = ScanPgRelation(RelationGetRelid(relation), indexOK);
	if (!HeapTupleIsValid(pg_class_tuple))
		elog(ERROR, "could not find pg_class tuple for index %u",
			 RelationGetRelid(relation));
	relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
	memcpy(relation->rd_rel, relp, CLASS_TUPLE_SIZE);
	/* Reload reloptions in case they changed */
	if (relation->rd_options)
		pfree(relation->rd_options);
	RelationParseRelOptions(relation, pg_class_tuple);
	/* done with pg_class tuple */
	heap_freetuple(pg_class_tuple);
	/* We must recalculate physical address in case it changed */
	RelationInitPhysicalAddr(relation);
	/* Make sure targblock is reset in case rel was truncated */
	relation->rd_targblock = InvalidBlockNumber;
	/* Must free any AM cached data, too */
	if (relation->rd_amcache)
		pfree(relation->rd_amcache);
	relation->rd_amcache = NULL;

	/*
	 * For a non-system index, there are fields of the pg_index row that are
	 * allowed to change, so re-read that row and update the relcache entry.
	 * Most of the info derived from pg_index (such as support function lookup
	 * info) cannot change, and indeed the whole point of this routine is to
	 * update the relcache entry without clobbering that data; so wholesale
	 * replacement is not appropriate.
	 */
	if (!IsSystemRelation(relation))
	{
		HeapTuple	tuple;
		Form_pg_index index;

		tuple = SearchSysCache(INDEXRELID,
							   ObjectIdGetDatum(RelationGetRelid(relation)),
							   0, 0, 0);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for index %u",
				 RelationGetRelid(relation));
		index = (Form_pg_index) GETSTRUCT(tuple);

		relation->rd_index->indisvalid = index->indisvalid;
		relation->rd_index->indcheckxmin = index->indcheckxmin;
		relation->rd_index->indisready = index->indisready;
		HeapTupleHeaderSetXmin(relation->rd_indextuple->t_data,
							   HeapTupleHeaderGetXmin(tuple->t_data));

		ReleaseSysCache(tuple);
	}

	/* Okay, now it's valid again */
	relation->rd_isvalid = true;
}

/*
 * 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