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Back-patch the 8.3 fix that prohibits TRUNCATE, CLUSTER, and REINDEX when the

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current transaction has any open references to the target relation or index
(implying it has an active query using the relation).  Also back-patch the
8.2 fix that prohibits TRUNCATE and CLUSTER when there are pending
AFTER-trigger events.  Per suggestion from Heikki.
This commit is contained in:
Tom Lane
2008-05-27 21:13:50 +00:00
parent b74150668d
commit bda5491729
6 changed files with 158 additions and 45 deletions
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101
src/backend/commands/tablecmds.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.142.4.9 2008/05/09 22:37:56 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.142.4.10 2008/05/27 21:13:50 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -577,6 +577,12 @@ TruncateRelation(const RangeVar *relation)
(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");
/*
* Don't allow truncate on tables which are referenced by foreign keys
*/
@@ -1776,6 +1782,55 @@ update_ri_trigger_args(Oid relid,
CommandCounterIncrement();
}
/*
* 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
@@ -1813,26 +1868,8 @@ 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));
}
@@ -1845,7 +1882,8 @@ 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)
@@ -2739,12 +2777,7 @@ 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);
}
@@ -2776,12 +2809,7 @@ 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);
}
@@ -3610,12 +3638,7 @@ 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 */