diff options
Diffstat (limited to 'src/backend/commands/tablecmds.c')
| -rw-r--r-- | src/backend/commands/tablecmds.c | 57 |
1 files changed, 50 insertions, 7 deletions
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 0aaf47a19dc..7e347b27f0e 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.206.2.1 2007/01/25 04:17:56 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.206.2.2 2007/02/02 00:07:27 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1950,22 +1950,47 @@ update_ri_trigger_args(Oid relid, void AlterTable(AlterTableStmt *stmt) { - ATController(relation_openrv(stmt->relation, AccessExclusiveLock), - stmt->cmds, - interpretInhOption(stmt->relation->inhOpt)); + Relation rel = relation_openrv(stmt->relation, AccessExclusiveLock); + int expected_refcnt; + + /* + * Disallow ALTER TABLE when the current backend has any open reference + * to it besides the one we just got (such as an open cursor or active + * plan); our AccessExclusiveLock doesn't protect us against stomping on + * our own foot, only other people's feet! + * + * Note: the only case known to cause serious trouble is ALTER COLUMN TYPE, + * and some changes are obviously pretty benign, so this could possibly + * be relaxed to only error out for certain types of alterations. But + * the use-case for allowing any of these things is not obvious, so we + * won't work hard at it for now. + */ + expected_refcnt = rel->rd_isnailed ? 2 : 1; + if (rel->rd_refcnt != expected_refcnt) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_IN_USE), + errmsg("relation \"%s\" is being used by active queries in this session", + RelationGetRelationName(rel)))); + + ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt)); } /* * AlterTableInternal * * ALTER TABLE with target specified by OID + * + * We do not reject if the relation is already open, because it's quite + * likely that one or more layers of caller have it open. That means it + * is unsafe to use this entry point for alterations that could break + * existing query plans. */ void AlterTableInternal(Oid relid, List *cmds, bool recurse) { - ATController(relation_open(relid, AccessExclusiveLock), - cmds, - recurse); + Relation rel = relation_open(relid, AccessExclusiveLock); + + ATController(rel, cmds, recurse); } static void @@ -2915,6 +2940,12 @@ ATSimpleRecursion(List **wqueue, Relation rel, if (childrelid == relid) continue; childrel = relation_open(childrelid, AccessExclusiveLock); + /* check for child relation in use in this session */ + if (childrel->rd_refcnt != 1) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_IN_USE), + errmsg("relation \"%s\" is being used by active queries in this session", + RelationGetRelationName(childrel)))); ATPrepCmd(wqueue, childrel, cmd, false, true); relation_close(childrel, NoLock); } @@ -2946,6 +2977,12 @@ ATOneLevelRecursion(List **wqueue, Relation rel, Relation childrel; childrel = relation_open(childrelid, AccessExclusiveLock); + /* check for child relation in use in this session */ + if (childrel->rd_refcnt != 1) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_IN_USE), + errmsg("relation \"%s\" is being used by active queries in this session", + RelationGetRelationName(childrel)))); ATPrepCmd(wqueue, childrel, cmd, true, true); relation_close(childrel, NoLock); } @@ -3745,6 +3782,12 @@ ATExecDropColumn(Relation rel, const char *colName, Form_pg_attribute childatt; childrel = heap_open(childrelid, AccessExclusiveLock); + /* check for child relation in use in this session */ + if (childrel->rd_refcnt != 1) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_IN_USE), + errmsg("relation \"%s\" is being used by active queries in this session", + RelationGetRelationName(childrel)))); tuple = SearchSysCacheCopyAttName(childrelid, colName); if (!HeapTupleIsValid(tuple)) /* shouldn't happen */ |