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

	relation->rd_att->tdhasoid = relation->rd_rel->relhasoids;

	constr = (TupleConstr *) MemoryContextAlloc(CacheMemoryContext,
												sizeof(TupleConstr));
	constr->has_not_null = false;

	/*
	 * Form a scan key that selects only user attributes (attnum > 0).
	 * (Eliminating system attribute rows at the index level is lots faster
	 * than fetching them.)
	 */
	ScanKeyInit(&skey[0],
				Anum_pg_attribute_attrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));
	ScanKeyInit(&skey[1],
				Anum_pg_attribute_attnum,
				BTGreaterStrategyNumber, F_INT2GT,
				Int16GetDatum(0));

	/*
	 * Open pg_attribute and begin a scan.	Force heap scan if we haven't yet
	 * built the critical relcache entries (this includes initdb and startup
	 * without a pg_internal.init file).
	 */
	pg_attribute_desc = heap_open(AttributeRelationId, AccessShareLock);
	pg_attribute_scan = systable_beginscan(pg_attribute_desc,
										   AttributeRelidNumIndexId,
										   criticalRelcachesBuilt,
										   SnapshotNow,
										   2, skey);

	/*
	 * add attribute data to relation->rd_att
	 */
	need = relation->rd_rel->relnatts;

	while (HeapTupleIsValid(pg_attribute_tuple = systable_getnext(pg_attribute_scan)))
	{
		Form_pg_attribute attp;

		attp = (Form_pg_attribute) GETSTRUCT(pg_attribute_tuple);

		if (attp->attnum <= 0 ||
			attp->attnum > relation->rd_rel->relnatts)
			elog(ERROR, "invalid attribute number %d for %s",
				 attp->attnum, RelationGetRelationName(relation));

		memcpy(relation->rd_att->attrs[attp->attnum - 1],
			   attp,
			   ATTRIBUTE_TUPLE_SIZE);

		/* Update constraint/default info */
		if (attp->attnotnull)
			constr->has_not_null = true;

		if (attp->atthasdef)
		{
			if (attrdef == NULL)
				attrdef = (AttrDefault *)
					MemoryContextAllocZero(CacheMemoryContext,
										   relation->rd_rel->relnatts *
										   sizeof(AttrDefault));
			attrdef[ndef].adnum = attp->attnum;
			attrdef[ndef].adbin = NULL;
			ndef++;
		}
		need--;
		if (need == 0)
			break;
	}

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

	if (need != 0)
		elog(ERROR, "catalog is missing %d attribute(s) for relid %u",
			 need, RelationGetRelid(relation));

	/*
	 * The attcacheoff values we read from pg_attribute should all be -1
	 * ("unknown").  Verify this if assert checking is on.	They will be
	 * computed when and if needed during tuple access.
	 */
#ifdef USE_ASSERT_CHECKING
	{
		int			i;

		for (i = 0; i < relation->rd_rel->relnatts; i++)
			Assert(relation->rd_att->attrs[i]->attcacheoff == -1);
	}
#endif

	/*
	 * However, we can easily set the attcacheoff value for the first
	 * attribute: it must be zero.	This eliminates the need for special cases
	 * for attnum=1 that used to exist in fastgetattr() and index_getattr().
	 */
	if (relation->rd_rel->relnatts > 0)
		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, IgnoreSystemIndexes). 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		rule_datum;
		text	   *rule_text;
		char	   *rule_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->enabled = rewrite_form->ev_enabled;
		rule->isInstead = rewrite_form->is_instead;

		/*
		 * Must use heap_getattr to fetch ev_action and ev_qual.  Also, the
		 * rule strings are often large enough to be toasted.  To avoid
		 * leaking memory in the caller's context, do the detoasting here so
		 * we can free the detoasted version.
		 */
		rule_datum = heap_getattr(rewrite_tuple,
								  Anum_pg_rewrite_ev_action,
								  rewrite_tupdesc,
								  &isnull);
		Assert(!isnull);
		rule_text = DatumGetTextP(rule_datum);
		rule_str = DatumGetCString(DirectFunctionCall1(textout,
												PointerGetDatum(rule_text)));
		oldcxt = MemoryContextSwitchTo(rulescxt);
		rule->actions = (List *) stringToNode(rule_str);
		MemoryContextSwitchTo(oldcxt);
		pfree(rule_str);
		if ((Pointer) rule_text != DatumGetPointer(rule_datum))
			pfree(rule_text);

		rule_datum = heap_getattr(rewrite_tuple,
								  Anum_pg_rewrite_ev_qual,
								  rewrite_tupdesc,
								  &isnull);
		Assert(!isnull);
		rule_text = DatumGetTextP(rule_datum);
		rule_str = DatumGetCString(DirectFunctionCall1(textout,
												PointerGetDatum(rule_text)));
		oldcxt = MemoryContextSwitchTo(rulescxt);
		rule->qual = (Node *) stringToNode(rule_str);
		MemoryContextSwitchTo(oldcxt);
		pfree(rule_str);
		if ((Pointer) rule_text != DatumGetPointer(rule_datum))
			pfree(rule_text);

		/*
		 * We want the rule's table references to be checked as though by the
		 * table owner, not the user referencing the rule.	Therefore, scan
		 * through the rule's actions and set the checkAsUser field on all
		 * rtable entries.	We have to look at the qual as well, in case it
		 * contains sublinks.
		 *
		 * The reason for doing this when the rule is loaded, rather than when
		 * it is stored, is that otherwise ALTER TABLE OWNER would have to
		 * grovel through stored rules to update checkAsUser fields. Scanning
		 * the rule tree during load is relatively cheap (compared to
		 * constructing it in the first place), so we do it here.
		 */
		setRuleCheckAsUser((Node *) rule->actions, relation->rd_rel->relowner);
		setRuleCheckAsUser(rule->qual, relation->rd_rel->relowner);

		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.  The caller must hold at least
 *		AccessShareLock on the target relid.
 *
 *		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.
 */
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);

	/*
	 * 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_newRelfilenodeSubid = InvalidSubTransactionId;
	relation->rd_istemp = isTempOrToastNamespace(relation->rd_rel->relnamespace);

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

	/*
	 * Fetch rules and triggers that affect this relation