relcache.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

		MemoryContextAllocZero(indexcxt, sizeof(RelationAmInfo));

	if (amstrategies > 0)
		operator = (Oid *)
			MemoryContextAllocZero(indexcxt,
								   natts * amstrategies * sizeof(Oid));
	else
		operator = NULL;

	if (amsupport > 0)
	{
		int			nsupport = natts * amsupport;

		support = (RegProcedure *)
			MemoryContextAllocZero(indexcxt, nsupport * sizeof(RegProcedure));
		supportinfo = (FmgrInfo *)
			MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
	}
	else
	{
		support = NULL;
		supportinfo = NULL;
	}

	relation->rd_operator = operator;
	relation->rd_support = support;
	relation->rd_supportinfo = supportinfo;

	/*
	 * Fill the operator and support procedure OID arrays.	(aminfo and
	 * supportinfo are left as zeroes, and are filled on-the-fly when used)
	 */
	IndexSupportInitialize(relation->rd_indclass,
						   operator, support,
						   amstrategies, amsupport, natts);

	/*
	 * expressions and predicate cache will be filled later
	 */
	relation->rd_indexprs = NIL;
	relation->rd_indpred = NIL;
}

/*
 * IndexSupportInitialize
 *		Initializes an index's cached opclass information,
 *		given the index's pg_index.indclass entry.
 *
 * Data is returned into *indexOperator and *indexSupport, which are arrays
 * allocated by the caller.
 *
 * The caller also passes maxStrategyNumber, maxSupportNumber, and
 * maxAttributeNumber, since these indicate the size of the arrays
 * it has allocated --- but in practice these numbers must always match
 * those obtainable from the system catalog entries for the index and
 * access method.
 */
static void
IndexSupportInitialize(oidvector *indclass,
					   Oid *indexOperator,
					   RegProcedure *indexSupport,
					   StrategyNumber maxStrategyNumber,
					   StrategyNumber maxSupportNumber,
					   AttrNumber maxAttributeNumber)
{
	int			attIndex;

	for (attIndex = 0; attIndex < maxAttributeNumber; attIndex++)
	{
		OpClassCacheEnt *opcentry;

		if (!OidIsValid(indclass->values[attIndex]))
			elog(ERROR, "bogus pg_index tuple");

		/* look up the info for this opclass, using a cache */
		opcentry = LookupOpclassInfo(indclass->values[attIndex],
									 maxStrategyNumber,
									 maxSupportNumber);

		/* copy cached data into relcache entry */
		if (maxStrategyNumber > 0)
			memcpy(&indexOperator[attIndex * maxStrategyNumber],
				   opcentry->operatorOids,
				   maxStrategyNumber * sizeof(Oid));
		if (maxSupportNumber > 0)
			memcpy(&indexSupport[attIndex * maxSupportNumber],
				   opcentry->supportProcs,
				   maxSupportNumber * sizeof(RegProcedure));
	}
}

/*
 * LookupOpclassInfo
 *
 * This routine maintains a per-opclass cache of the information needed
 * by IndexSupportInitialize().  This is more efficient than relying on
 * the catalog cache, because we can load all the info about a particular
 * opclass in a single indexscan of pg_amproc or pg_amop.
 *
 * The information from pg_am about expected range of strategy and support
 * numbers is passed in, rather than being looked up, mainly because the
 * caller will have it already.
 *
 * XXX There isn't any provision for flushing the cache.  However, there
 * isn't any provision for flushing relcache entries when opclass info
 * changes, either :-(
 */
static OpClassCacheEnt *
LookupOpclassInfo(Oid operatorClassOid,
				  StrategyNumber numStrats,
				  StrategyNumber numSupport)
{
	OpClassCacheEnt *opcentry;
	bool		found;
	Relation	rel;
	SysScanDesc scan;
	ScanKeyData skey[2];
	HeapTuple	htup;
	bool		indexOK;

	if (OpClassCache == NULL)
	{
		/* First time through: initialize the opclass cache */
		HASHCTL		ctl;

		if (!CacheMemoryContext)
			CreateCacheMemoryContext();

		MemSet(&ctl, 0, sizeof(ctl));
		ctl.keysize = sizeof(Oid);
		ctl.entrysize = sizeof(OpClassCacheEnt);
		ctl.hash = oid_hash;
		OpClassCache = hash_create("Operator class cache", 64,
								   &ctl, HASH_ELEM | HASH_FUNCTION);
	}

	opcentry = (OpClassCacheEnt *) hash_search(OpClassCache,
											   (void *) &operatorClassOid,
											   HASH_ENTER, &found);

	if (found && opcentry->valid)
	{
		/* Already made an entry for it */
		Assert(numStrats == opcentry->numStrats);
		Assert(numSupport == opcentry->numSupport);
		return opcentry;
	}

	/* Need to fill in new entry */
	opcentry->valid = false;	/* until known OK */
	opcentry->numStrats = numStrats;
	opcentry->numSupport = numSupport;

	if (numStrats > 0)
		opcentry->operatorOids = (Oid *)
			MemoryContextAllocZero(CacheMemoryContext,
								   numStrats * sizeof(Oid));
	else
		opcentry->operatorOids = NULL;

	if (numSupport > 0)
		opcentry->supportProcs = (RegProcedure *)
			MemoryContextAllocZero(CacheMemoryContext,
								   numSupport * sizeof(RegProcedure));
	else
		opcentry->supportProcs = NULL;

	/*
	 * To avoid infinite recursion during startup, force heap scans if we're
	 * looking up info for the opclasses used by the indexes we would like to
	 * reference here.
	 */
	indexOK = criticalRelcachesBuilt ||
		(operatorClassOid != OID_BTREE_OPS_OID &&
		 operatorClassOid != INT2_BTREE_OPS_OID);

	/*
	 * Scan pg_amop to obtain operators for the opclass.  We only fetch the
	 * default ones (those with subtype zero).
	 */
	if (numStrats > 0)
	{
		ScanKeyInit(&skey[0],
					Anum_pg_amop_amopclaid,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(operatorClassOid));
		ScanKeyInit(&skey[1],
					Anum_pg_amop_amopsubtype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(InvalidOid));
		rel = heap_open(AccessMethodOperatorRelationId, AccessShareLock);
		scan = systable_beginscan(rel, AccessMethodStrategyIndexId, indexOK,
								  SnapshotNow, 2, skey);

		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 subtype zero).
	 */
	if (numSupport > 0)
	{
		ScanKeyInit(&skey[0],
					Anum_pg_amproc_amopclaid,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(operatorClassOid));
		ScanKeyInit(&skey[1],
					Anum_pg_amproc_amprocsubtype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(InvalidOid));
		rel = heap_open(AccessMethodProcedureRelationId, AccessShareLock);
		scan = systable_beginscan(rel, AccessMethodProcedureIndexId, indexOK,
								  SnapshotNow, 2, 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 RelationCacheInitialize() 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 RelationCacheInitialize).
 *
 * 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_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->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
 * ----------------------------------------------------------------
 */

/*
 *		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_isvalid)
			RelationReloadClassinfo(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;