relcache.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

		relation->rd_att->attrs[0]->attcacheoff = 0;

	/*
	 * Set up constraint/default info
	 */
	if (constr->has_not_null || ndef > 0 || relation->rd_rel->relchecks)
	{
		relation->rd_att->constr = constr;

		if (ndef > 0)			/* DEFAULTs */
		{
			if (ndef < relation->rd_rel->relnatts)
				constr->defval = (AttrDefault *)
					repalloc(attrdef, ndef * sizeof(AttrDefault));
			else
				constr->defval = attrdef;
			constr->num_defval = ndef;
			AttrDefaultFetch(relation);
		}
		else
			constr->num_defval = 0;

		if (relation->rd_rel->relchecks > 0)	/* CHECKs */
		{
			constr->num_check = relation->rd_rel->relchecks;
			constr->check = (ConstrCheck *)
				MemoryContextAllocZero(CacheMemoryContext,
									constr->num_check * sizeof(ConstrCheck));
			CheckConstraintFetch(relation);
		}
		else
			constr->num_check = 0;
	}
	else
	{
		pfree(constr);
		relation->rd_att->constr = NULL;
	}
}

/*
 *		RelationBuildRuleLock
 *
 *		Form the relation's rewrite rules from information in
 *		the pg_rewrite system catalog.
 *
 * Note: The rule parsetrees are potentially very complex node structures.
 * To allow these trees to be freed when the relcache entry is flushed,
 * we make a private memory context to hold the RuleLock information for
 * each relcache entry that has associated rules.  The context is used
 * just for rule info, not for any other subsidiary data of the relcache
 * entry, because that keeps the update logic in RelationClearRelation()
 * manageable.	The other subsidiary data structures are simple enough
 * to be easy to free explicitly, anyway.
 */
static void
RelationBuildRuleLock(Relation relation)
{
	MemoryContext rulescxt;
	MemoryContext oldcxt;
	HeapTuple	rewrite_tuple;
	Relation	rewrite_desc;
	TupleDesc	rewrite_tupdesc;
	SysScanDesc rewrite_scan;
	ScanKeyData key;
	RuleLock   *rulelock;
	int			numlocks;
	RewriteRule **rules;
	int			maxlocks;

	/*
	 * Make the private context.  Parameters are set on the assumption that
	 * it'll probably not contain much data.
	 */
	rulescxt = AllocSetContextCreate(CacheMemoryContext,
									 RelationGetRelationName(relation),
									 ALLOCSET_SMALL_MINSIZE,
									 ALLOCSET_SMALL_INITSIZE,
									 ALLOCSET_SMALL_MAXSIZE);
	relation->rd_rulescxt = rulescxt;

	/*
	 * allocate an array to hold the rewrite rules (the array is extended if
	 * necessary)
	 */
	maxlocks = 4;
	rules = (RewriteRule **)
		MemoryContextAlloc(rulescxt, sizeof(RewriteRule *) * maxlocks);
	numlocks = 0;

	/*
	 * form a scan key
	 */
	ScanKeyInit(&key,
				Anum_pg_rewrite_ev_class,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));

	/*
	 * open pg_rewrite and begin a scan
	 *
	 * Note: since we scan the rules using RewriteRelRulenameIndexId, we will
	 * be reading the rules in name order, except possibly during
	 * emergency-recovery operations (ie, IsIgnoringSystemIndexes). This in
	 * turn ensures that rules will be fired in name order.
	 */
	rewrite_desc = heap_open(RewriteRelationId, AccessShareLock);
	rewrite_tupdesc = RelationGetDescr(rewrite_desc);
	rewrite_scan = systable_beginscan(rewrite_desc,
									  RewriteRelRulenameIndexId,
									  true, SnapshotNow,
									  1, &key);

	while (HeapTupleIsValid(rewrite_tuple = systable_getnext(rewrite_scan)))
	{
		Form_pg_rewrite rewrite_form = (Form_pg_rewrite) GETSTRUCT(rewrite_tuple);
		bool		isnull;
		Datum		ruleaction;
		Datum		rule_evqual;
		char	   *ruleaction_str;
		char	   *rule_evqual_str;
		RewriteRule *rule;

		rule = (RewriteRule *) MemoryContextAlloc(rulescxt,
												  sizeof(RewriteRule));

		rule->ruleId = HeapTupleGetOid(rewrite_tuple);

		rule->event = rewrite_form->ev_type - '0';
		rule->attrno = rewrite_form->ev_attr;
		rule->isInstead = rewrite_form->is_instead;

		/* Must use heap_getattr to fetch ev_qual and ev_action */

		ruleaction = heap_getattr(rewrite_tuple,
								  Anum_pg_rewrite_ev_action,
								  rewrite_tupdesc,
								  &isnull);
		Assert(!isnull);
		ruleaction_str = DatumGetCString(DirectFunctionCall1(textout,
															 ruleaction));
		oldcxt = MemoryContextSwitchTo(rulescxt);
		rule->actions = (List *) stringToNode(ruleaction_str);
		MemoryContextSwitchTo(oldcxt);
		pfree(ruleaction_str);

		rule_evqual = heap_getattr(rewrite_tuple,
								   Anum_pg_rewrite_ev_qual,
								   rewrite_tupdesc,
								   &isnull);
		Assert(!isnull);
		rule_evqual_str = DatumGetCString(DirectFunctionCall1(textout,
															  rule_evqual));
		oldcxt = MemoryContextSwitchTo(rulescxt);
		rule->qual = (Node *) stringToNode(rule_evqual_str);
		MemoryContextSwitchTo(oldcxt);
		pfree(rule_evqual_str);

		if (numlocks >= maxlocks)
		{
			maxlocks *= 2;
			rules = (RewriteRule **)
				repalloc(rules, sizeof(RewriteRule *) * maxlocks);
		}
		rules[numlocks++] = rule;
	}

	/*
	 * end the scan and close the attribute relation
	 */
	systable_endscan(rewrite_scan);
	heap_close(rewrite_desc, AccessShareLock);

	/*
	 * form a RuleLock and insert into relation
	 */
	rulelock = (RuleLock *) MemoryContextAlloc(rulescxt, sizeof(RuleLock));
	rulelock->numLocks = numlocks;
	rulelock->rules = rules;

	relation->rd_rules = rulelock;
}

/*
 *		equalRuleLocks
 *
 *		Determine whether two RuleLocks are equivalent
 *
 *		Probably this should be in the rules code someplace...
 */
static bool
equalRuleLocks(RuleLock *rlock1, RuleLock *rlock2)
{
	int			i;

	/*
	 * As of 7.3 we assume the rule ordering is repeatable, because
	 * RelationBuildRuleLock should read 'em in a consistent order.  So just
	 * compare corresponding slots.
	 */
	if (rlock1 != NULL)
	{
		if (rlock2 == NULL)
			return false;
		if (rlock1->numLocks != rlock2->numLocks)
			return false;
		for (i = 0; i < rlock1->numLocks; i++)
		{
			RewriteRule *rule1 = rlock1->rules[i];
			RewriteRule *rule2 = rlock2->rules[i];

			if (rule1->ruleId != rule2->ruleId)
				return false;
			if (rule1->event != rule2->event)
				return false;
			if (rule1->attrno != rule2->attrno)
				return false;
			if (rule1->isInstead != rule2->isInstead)
				return false;
			if (!equal(rule1->qual, rule2->qual))
				return false;
			if (!equal(rule1->actions, rule2->actions))
				return false;
		}
	}
	else if (rlock2 != NULL)
		return false;
	return true;
}


/* ----------------------------------
 *		RelationBuildDesc
 *
 *		Build a relation descriptor --- either a new one, or by
 *		recycling the given old relation object.  The latter case
 *		supports rebuilding a relcache entry without invalidating
 *		pointers to it.
 * --------------------------------
 */
static Relation
RelationBuildDesc(Oid targetRelId, Relation oldrelation)
{
	Relation	relation;
	Oid			relid;
	HeapTuple	pg_class_tuple;
	Form_pg_class relp;
	MemoryContext oldcxt;

	/*
	 * find the tuple in pg_class corresponding to the given relation id
	 */
	pg_class_tuple = ScanPgRelation(targetRelId, true);

	/*
	 * if no such tuple exists, return NULL
	 */
	if (!HeapTupleIsValid(pg_class_tuple))
		return NULL;

	/*
	 * get information from the pg_class_tuple
	 */
	relid = HeapTupleGetOid(pg_class_tuple);
	relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);

	/*
	 * allocate storage for the relation descriptor, and copy pg_class_tuple
	 * to relation->rd_rel.
	 */
	relation = AllocateRelationDesc(oldrelation, relp);

	/*
	 * now we can free the memory allocated for pg_class_tuple
	 */
	heap_freetuple(pg_class_tuple);

	/*
	 * initialize the relation's relation id (relation->rd_id)
	 */
	RelationGetRelid(relation) = relid;

	/*
	 * normal relations are not nailed into the cache; nor can a pre-existing
	 * relation be new.  It could be temp though.  (Actually, it could be new
	 * too, but it's okay to forget that fact if forced to flush the entry.)
	 */
	relation->rd_refcnt = 0;
	relation->rd_isnailed = false;
	relation->rd_createSubid = InvalidSubTransactionId;
	relation->rd_istemp = isTempNamespace(relation->rd_rel->relnamespace);

	/*
	 * initialize the tuple descriptor (relation->rd_att).
	 */
	RelationBuildTupleDesc(relation);

	/*
	 * Fetch rules and triggers that affect this relation
	 */
	if (relation->rd_rel->relhasrules)
		RelationBuildRuleLock(relation);
	else
	{
		relation->rd_rules = NULL;
		relation->rd_rulescxt = NULL;
	}

	if (relation->rd_rel->reltriggers > 0)
		RelationBuildTriggers(relation);
	else
		relation->trigdesc = NULL;

	/*
	 * if it's an index, initialize index-related information
	 */
	if (OidIsValid(relation->rd_rel->relam))
		RelationInitIndexAccessInfo(relation);

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

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

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

	/*
	 * Insert newly created relation into relcache hash tables.
	 */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
	RelationCacheInsert(relation);
	MemoryContextSwitchTo(oldcxt);

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

	return relation;
}

/*
 * Initialize the physical addressing info (RelFileNode) for a relcache entry
 */
static void
RelationInitPhysicalAddr(Relation relation)
{
	if (relation->rd_rel->reltablespace)
		relation->rd_node.spcNode = relation->rd_rel->reltablespace;
	else
		relation->rd_node.spcNode = MyDatabaseTableSpace;
	if (relation->rd_rel->relisshared)
		relation->rd_node.dbNode = InvalidOid;
	else
		relation->rd_node.dbNode = MyDatabaseId;
	relation->rd_node.relNode = relation->rd_rel->relfilenode;
}

/*
 * Initialize index-access-method support data for an index relation
 */
void
RelationInitIndexAccessInfo(Relation relation)
{
	HeapTuple	tuple;
	Form_pg_am	aform;
	Datum		indclassDatum;
	bool		isnull;
	MemoryContext indexcxt;
	MemoryContext oldcontext;
	Oid		   *operator;
	RegProcedure *support;
	FmgrInfo   *supportinfo;
	int			natts;
	uint16		amstrategies;
	uint16		amsupport;

	/*
	 * Make a copy of the pg_index entry for the index.  Since pg_index
	 * contains variable-length and possibly-null fields, we have to do this
	 * honestly rather than just treating it as a Form_pg_index struct.
	 */
	tuple = SearchSysCache(INDEXRELID,
						   ObjectIdGetDatum(RelationGetRelid(relation)),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for index %u",
			 RelationGetRelid(relation));
	oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
	relation->rd_indextuple = heap_copytuple(tuple);
	relation->rd_index = (Form_pg_index) GETSTRUCT(relation->rd_indextuple);
	MemoryContextSwitchTo(oldcontext);
	ReleaseSysCache(tuple);

	/*
	 * indclass cannot be referenced directly through the C struct, because it
	 * is after the variable-width indkey field.  Therefore we extract the
	 * datum the hard way and provide a direct link in the relcache.
	 */
	indclassDatum = fastgetattr(relation->rd_indextuple,
								Anum_pg_index_indclass,
								GetPgIndexDescriptor(),
								&isnull);
	Assert(!isnull);
	relation->rd_indclass = (oidvector *) DatumGetPointer(indclassDatum);

	/*
	 * Make a copy of the pg_am entry for the index's access method
	 */
	tuple = SearchSysCache(AMOID,
						   ObjectIdGetDatum(relation->rd_rel->relam),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for access method %u",
			 relation->rd_rel->relam);
	aform = (Form_pg_am) MemoryContextAlloc(CacheMemoryContext, sizeof *aform);
	memcpy(aform, GETSTRUCT(tuple), sizeof *aform);
	ReleaseSysCache(tuple);
	relation->rd_am = aform;

	natts = relation->rd_rel->relnatts;
	if (natts != relation->rd_index->indnatts)
		elog(ERROR, "relnatts disagrees with indnatts for index %u",
			 RelationGetRelid(relation));
	amstrategies = aform->amstrategies;
	amsupport = aform->amsupport;

	/*
	 * Make the private context to hold index access info.	The reason we need
	 * a context, and not just a couple of pallocs, is so that we won't leak
	 * any subsidiary info attached to fmgr lookup records.
	 *
	 * Context parameters are set on the assumption that it'll probably not
	 * contain much data.
	 */
	indexcxt = AllocSetContextCreate(CacheMemoryContext,
									 RelationGetRelationName(relation),
									 ALLOCSET_SMALL_MINSIZE,
									 ALLOCSET_SMALL_INITSIZE,
									 ALLOCSET_SMALL_MAXSIZE);
	relation->rd_indexcxt = indexcxt;

	/*
	 * Allocate arrays to hold data
	 */
	relation->rd_aminfo = (RelationAmInfo *)