diff options
Diffstat (limited to 'src/backend/commands/tablecmds.c')
| -rw-r--r-- | src/backend/commands/tablecmds.c | 101 |
1 files changed, 62 insertions, 39 deletions
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index e0f87865078..1350b0d0269 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 1.174.2.6 2008/05/09 22:37:47 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.174.2.7 2008/05/27 21:13:39 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -588,6 +588,12 @@ ExecuteTruncate(List *relations) (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot truncate temporary tables of other sessions"))); + /* + * Also check for active uses of the relation in the current + * transaction, including open scans and pending AFTER trigger events. + */ + CheckTableNotInUse(rel, "TRUNCATE"); + /* Save it into the list of rels to truncate */ rels = lappend(rels, rel); } @@ -1764,6 +1770,55 @@ update_ri_trigger_args(Oid relid, } /* + * Disallow ALTER TABLE (and similar commands) when the current backend has + * any open reference to the target table besides the one just acquired by + * the calling command; this implies there's an open cursor or active plan. + * We need this check because our AccessExclusiveLock doesn't protect us + * against stomping on our own foot, only other people's feet! + * + * For ALTER TABLE, 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. + * + * We also reject these commands if there are any pending AFTER trigger events + * for the rel. This is certainly necessary for the rewriting variants of + * ALTER TABLE, because they don't preserve tuple TIDs and so the pending + * events would try to fetch the wrong tuples. It might be overly cautious + * in other cases, but again it seems better to err on the side of paranoia. + * + * REINDEX calls this with "rel" referencing the index to be rebuilt; here + * we are worried about active indexscans on the index. The trigger-event + * check can be skipped, since we are doing no damage to the parent table. + * + * The statement name (eg, "ALTER TABLE") is passed for use in error messages. + */ +void +CheckTableNotInUse(Relation rel, const char *stmt) +{ + int expected_refcnt; + + expected_refcnt = rel->rd_isnailed ? 2 : 1; + if (rel->rd_refcnt != expected_refcnt) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_IN_USE), + /* translator: first %s is a SQL command, eg ALTER TABLE */ + errmsg("cannot %s \"%s\" because " + "it is being used by active queries in this session", + stmt, RelationGetRelationName(rel)))); + + if (rel->rd_rel->relkind != RELKIND_INDEX && + AfterTriggerPendingOnRel(RelationGetRelid(rel))) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_IN_USE), + /* translator: first %s is a SQL command, eg ALTER TABLE */ + errmsg("cannot %s \"%s\" because " + "it has pending trigger events", + stmt, RelationGetRelationName(rel)))); +} + +/* * AlterTable * Execute ALTER TABLE, which can be a list of subcommands * @@ -1800,26 +1855,8 @@ void AlterTable(AlterTableStmt *stmt) { 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)))); + CheckTableNotInUse(rel, "ALTER TABLE"); ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt)); } @@ -1832,7 +1869,8 @@ AlterTable(AlterTableStmt *stmt) * 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. + * existing query plans. On the assumption it's not used for such, we + * don't have to reject pending AFTER triggers, either. */ void AlterTableInternal(Oid relid, List *cmds, bool recurse) @@ -2744,12 +2782,7 @@ 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)))); + CheckTableNotInUse(childrel, "ALTER TABLE"); ATPrepCmd(wqueue, childrel, cmd, false, true); relation_close(childrel, NoLock); } @@ -2781,12 +2814,7 @@ 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)))); + CheckTableNotInUse(childrel, "ALTER TABLE"); ATPrepCmd(wqueue, childrel, cmd, true, true); relation_close(childrel, NoLock); } @@ -3613,12 +3641,7 @@ 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)))); + CheckTableNotInUse(childrel, "ALTER TABLE"); tuple = SearchSysCacheCopyAttName(childrelid, colName); if (!HeapTupleIsValid(tuple)) /* shouldn't happen */ |