From f8bbfad075e855d4603e44847cd6ec51c91b3f92 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 4 Sep 2006 21:15:56 +0000
Subject: [PATCH] Disallow TRUNCATE when there are any pending after-trigger
events for the target relation(s). There might be some cases where we could
discard the pending event instead, but for the moment a conservative approach
seems sufficient. Per report from Markus Schiltknecht and subsequent
discussion.
---
src/backend/commands/tablecmds.c | 9 +++-
src/backend/commands/trigger.c | 70 +++++++++++++++++++++++++++++++-
src/include/commands/trigger.h | 4 +-
3 files changed, 79 insertions(+), 4 deletions(-)
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 7e8884496d0..45167b816af 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 1.201 2006/08/25 04:06:48 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.202 2006/09/04 21:15:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -611,6 +611,13 @@ ExecuteTruncate(TruncateStmt *stmt)
heap_truncate_check_FKs(rels, false);
#endif
+ /*
+ * Also check for pending AFTER trigger events on the target relations.
+ * We can't just leave those be, since they will try to fetch tuples
+ * that the TRUNCATE removes.
+ */
+ AfterTriggerCheckTruncate(relids);
+
/*
* OK, truncate each table.
*/
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 42d89a9a21a..23dc5030397 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.206 2006/08/03 16:04:41 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.207 2006/09/04 21:15:56 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -3117,6 +3117,74 @@ AfterTriggerSetState(ConstraintsSetStmt *stmt)
}
}
+/* ----------
+ * AfterTriggerCheckTruncate()
+ * Test deferred-trigger status to see if a TRUNCATE is OK.
+ *
+ * The argument is a list of OIDs of relations due to be truncated.
+ * We raise error if there are any pending after-trigger events for them.
+ *
+ * In some scenarios it'd be reasonable to remove pending events (more
+ * specifically, mark them DONE by the current subxact) but without a lot
+ * of knowledge of the trigger semantics we can't do this in general.
+ * ----------
+ */
+void
+AfterTriggerCheckTruncate(List *relids)
+{
+ AfterTriggerEvent event;
+ int depth;
+
+ /*
+ * Ignore call if we aren't in a transaction. (Shouldn't happen?)
+ */
+ if (afterTriggers == NULL)
+ return;
+
+ /* Scan queued events */
+ for (event = afterTriggers->events.head;
+ event != NULL;
+ event = event->ate_next)
+ {
+ /*
+ * We can ignore completed events. (Even if a DONE flag is rolled
+ * back by subxact abort, it's OK because the effects of the
+ * TRUNCATE must get rolled back too.)
+ */
+ if (event->ate_event & AFTER_TRIGGER_DONE)
+ continue;
+
+ if (list_member_oid(relids, event->ate_relid))
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot truncate table \"%s\" because it has pending trigger events",
+ get_rel_name(event->ate_relid))));
+ }
+
+ /*
+ * Also scan events queued by incomplete queries. This could only
+ * matter if a TRUNCATE is executed by a function or trigger within
+ * an updating query on the same relation, which is pretty perverse,
+ * but let's check.
+ */
+ for (depth = 0; depth <= afterTriggers->query_depth; depth++)
+ {
+ for (event = afterTriggers->query_stack[depth].head;
+ event != NULL;
+ event = event->ate_next)
+ {
+ if (event->ate_event & AFTER_TRIGGER_DONE)
+ continue;
+
+ if (list_member_oid(relids, event->ate_relid))
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot truncate table \"%s\" because it has pending trigger events",
+ get_rel_name(event->ate_relid))));
+ }
+ }
+}
+
/* ----------
* AfterTriggerSaveEvent()
diff --git a/src/include/commands/trigger.h b/src/include/commands/trigger.h
index 0cb4df7c4fa..31253d8b4fe 100644
--- a/src/include/commands/trigger.h
+++ b/src/include/commands/trigger.h
@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/commands/trigger.h,v 1.58 2006/06/16 20:23:45 adunstan Exp $
+ * $PostgreSQL: pgsql/src/include/commands/trigger.h,v 1.59 2006/09/04 21:15:56 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -164,8 +164,8 @@ extern void AfterTriggerFireDeferred(void);
extern void AfterTriggerEndXact(bool isCommit);
extern void AfterTriggerBeginSubXact(void);
extern void AfterTriggerEndSubXact(bool isCommit);
-
extern void AfterTriggerSetState(ConstraintsSetStmt *stmt);
+extern void AfterTriggerCheckTruncate(List *relids);
/*
--
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