rewritedefine.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 588 行 · 第 1/2 页

			if (resdom->resjunk)
				continue;
			i++;
			if (i > event_relation->rd_att->natts)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("SELECT rule's target list has too many entries")));

			attr = event_relation->rd_att->attrs[i - 1];
			attname = NameStr(attr->attname);

			/*
			 * Disallow dropped columns in the relation.  This won't
			 * happen in the cases we actually care about (namely creating
			 * a view via CREATE TABLE then CREATE RULE).  Trying to cope
			 * with it is much more trouble than it's worth, because we'd
			 * have to modify the rule to insert dummy NULLs at the right
			 * positions.
			 */
			if (attr->attisdropped)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot convert relation containing dropped columns to view")));

			if (strcmp(resdom->resname, attname) != 0)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("SELECT rule's target entry %d has different column name from \"%s\"", i, attname)));

			if (attr->atttypid != resdom->restype)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("SELECT rule's target entry %d has different type from column \"%s\"", i, attname)));

			/*
			 * Allow typmods to be different only if one of them is -1,
			 * ie, "unspecified".  This is necessary for cases like
			 * "numeric", where the table will have a filled-in default
			 * length but the select rule's expression will probably have
			 * typmod = -1.
			 */
			if (attr->atttypmod != resdom->restypmod &&
				attr->atttypmod != -1 && resdom->restypmod != -1)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("SELECT rule's target entry %d has different size from column \"%s\"", i, attname)));
		}

		if (i != event_relation->rd_att->natts)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
			   errmsg("SELECT rule's target list has too few entries")));

		/*
		 * ... there must not be another ON SELECT rule already ...
		 */
		if (!replace && event_relation->rd_rules != NULL)
		{
			for (i = 0; i < event_relation->rd_rules->numLocks; i++)
			{
				RewriteRule *rule;

				rule = event_relation->rd_rules->rules[i];
				if (rule->event == CMD_SELECT)
					ereport(ERROR,
					  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					   errmsg("\"%s\" is already a view",
							  RelationGetRelationName(event_relation))));
			}
		}

		/*
		 * ... and finally the rule must be named _RETURN.
		 */
		if (strcmp(stmt->rulename, ViewSelectRuleName) != 0)
		{
			/*
			 * In versions before 7.3, the expected name was _RETviewname.
			 * For backwards compatibility with old pg_dump output, accept
			 * that and silently change it to _RETURN.	Since this is just
			 * a quick backwards-compatibility hack, limit the number of
			 * characters checked to a few less than NAMEDATALEN; this
			 * saves having to worry about where a multibyte character
			 * might have gotten truncated.
			 */
			if (strncmp(stmt->rulename, "_RET", 4) != 0 ||
				strncmp(stmt->rulename + 4, event_obj->relname,
						NAMEDATALEN - 4 - 4) != 0)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
					  errmsg("view rule for \"%s\" must be named \"%s\"",
							 event_obj->relname, ViewSelectRuleName)));
			stmt->rulename = pstrdup(ViewSelectRuleName);
		}

		/*
		 * Are we converting a relation to a view?
		 *
		 * If so, check that the relation is empty because the storage for
		 * the relation is going to be deleted.  Also insist that the rel
		 * not have any triggers, indexes, or child tables.
		 */
		if (event_relation->rd_rel->relkind != RELKIND_VIEW)
		{
			HeapScanDesc scanDesc;

			scanDesc = heap_beginscan(event_relation, SnapshotNow, 0, NULL);
			if (heap_getnext(scanDesc, ForwardScanDirection) != NULL)
				ereport(ERROR,
					  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				errmsg("could not convert table \"%s\" to a view because it is not empty",
					   event_obj->relname)));
			heap_endscan(scanDesc);

			if (event_relation->rd_rel->reltriggers != 0)
				ereport(ERROR,
						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
						 errmsg("could not convert table \"%s\" to a view because it has triggers",
								event_obj->relname),
						 errhint("In particular, the table may not be involved in any foreign key relationships.")));

			if (event_relation->rd_rel->relhasindex)
				ereport(ERROR,
						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
						 errmsg("could not convert table \"%s\" to a view because it has indexes",
								event_obj->relname)));

			if (event_relation->rd_rel->relhassubclass)
				ereport(ERROR,
						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
						 errmsg("could not convert table \"%s\" to a view because it has child tables",
								event_obj->relname)));

			RelisBecomingView = true;
		}
	}

	/*
	 * This rule is allowed - prepare to install it.
	 */
	event_attno = -1;
	event_attype = InvalidOid;

	/*
	 * We want the rule's table references to be checked as though by the
	 * rule owner, not the user referencing the rule.  Therefore, scan
	 * through the rule's rtables and set the checkAsUser field on all
	 * rtable entries.
	 */
	foreach(l, action)
	{
		query = (Query *) lfirst(l);
		setRuleCheckAsUser(query, GetUserId());
	}

	/* discard rule if it's null action and not INSTEAD; it's a no-op */
	if (action != NIL || is_instead)
	{
		ruleId = InsertRule(stmt->rulename,
							event_type,
							ev_relid,
							event_attno,
							is_instead,
							event_qual,
							action,
							replace);

		/*
		 * Set pg_class 'relhasrules' field TRUE for event relation. If
		 * appropriate, also modify the 'relkind' field to show that the
		 * relation is now a view.
		 *
		 * Important side effect: an SI notice is broadcast to force all
		 * backends (including me!) to update relcache entries with the
		 * new rule.
		 */
		SetRelationRuleStatus(ev_relid, true, RelisBecomingView);
	}

	/*
	 * IF the relation is becoming a view, delete the storage files
	 * associated with it.	NB: we had better have AccessExclusiveLock to
	 * do this ...
	 *
	 * XXX what about getting rid of its TOAST table?  For now, we don't.
	 */
	if (RelisBecomingView)
		smgrunlink(DEFAULT_SMGR, event_relation);

	/* Close rel, but keep lock till commit... */
	heap_close(event_relation, NoLock);
}

/*
 * setRuleCheckAsUser
 *		Recursively scan a query and set the checkAsUser field to the
 *		given userid in all rtable entries.
 *
 * Note: for a view (ON SELECT rule), the checkAsUser field of the *OLD*
 * RTE entry will be overridden when the view rule is expanded, and the
 * checkAsUser field of the *NEW* entry is irrelevant because that entry's
 * checkFor bits will never be set.  However, for other types of rules it's
 * important to set these fields to match the rule owner.  So we just set
 * them always.
 */
static void
setRuleCheckAsUser(Query *qry, AclId userid)
{
	List	   *l;

	/* Set all the RTEs in this query node */
	foreach(l, qry->rtable)
	{
		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);

		if (rte->rtekind == RTE_SUBQUERY)
		{
			/* Recurse into subquery in FROM */
			setRuleCheckAsUser(rte->subquery, userid);
		}
		else
			rte->checkAsUser = userid;
	}

	/* If there are sublinks, search for them and process their RTEs */
	/* ignore subqueries in rtable because we already processed them */
	if (qry->hasSubLinks)
		query_tree_walker(qry, setRuleCheckAsUser_walker, (void *) &userid,
						  QTW_IGNORE_RT_SUBQUERIES);
}

/*
 * Expression-tree walker to find sublink queries
 */
static bool
setRuleCheckAsUser_walker(Node *node, Oid *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Query))
	{
		Query	   *qry = (Query *) node;

		setRuleCheckAsUser(qry, *context);
		return false;
	}
	return expression_tree_walker(node, setRuleCheckAsUser_walker,
								  (void *) context);
}


/*
 * Rename an existing rewrite rule.
 *
 * This is unused code at the moment.
 */
void
RenameRewriteRule(Oid owningRel, const char *oldName,
				  const char *newName)
{
	Relation	pg_rewrite_desc;
	HeapTuple	ruletup;

	pg_rewrite_desc = heap_openr(RewriteRelationName, RowExclusiveLock);

	ruletup = SearchSysCacheCopy(RULERELNAME,
								 ObjectIdGetDatum(owningRel),
								 PointerGetDatum(oldName),
								 0, 0);
	if (!HeapTupleIsValid(ruletup))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("rule \"%s\" for relation \"%s\" does not exist",
						oldName, get_rel_name(owningRel))));

	/* should not already exist */
	if (IsDefinedRewriteRule(owningRel, newName))
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_OBJECT),
				 errmsg("rule \"%s\" for relation \"%s\" already exists",
						newName, get_rel_name(owningRel))));

	namestrcpy(&(((Form_pg_rewrite) GETSTRUCT(ruletup))->rulename), newName);

	simple_heap_update(pg_rewrite_desc, &ruletup->t_self, ruletup);

	/* keep system catalog indexes current */
	CatalogUpdateIndexes(pg_rewrite_desc, ruletup);

	heap_freetuple(ruletup);
	heap_close(pg_rewrite_desc, RowExclusiveLock);
}