mdtruncate throws an error if the relation file doesn't exist. However,
that's not an error condition if the relation was dropped later.
Non-existent file should be treated the same as an already truncated
file; we now end up with an unrecoverable database.
This bug seems to be present from 8.0 onwards.
Attached is a test case to reproduce it, along with a patch for CVS
HEAD, and an adapted version of the patch for 8.0-8.2.
Thanks to my colleague Dharmendra Goyal for finding this bug and
constructing an initial test case.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
DROP TABLE test;
CREATE TABLE test(i char(1800));
BEGIN;
INSERT INTO test VALUES('a');
ROLLBACK;
-- Crash database. This leaves behind an unitialized page at the end of the
-- relation, which vacuum will then truncate.
\! DATA=`psql regression -t -c 'show data_directory'`&& echo $DATA; pg_ctl restart -w -m immediate -D $DATA
\c regression;
VACUUM test;
DROP TABLE test;
-- Crash database
\! DATA=`psql regression -t -c 'show data_directory'`&& echo $DATA; pg_ctl restart -w -m immediate -D $DATA
\c regression;
Index: src/backend/storage/smgr/md.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/storage/smgr/md.c,v
retrieving revision 1.128
diff -c -r1.128 md.c
*** src/backend/storage/smgr/md.c 12 Apr 2007 17:10:55 -0000 1.128
--- src/backend/storage/smgr/md.c 20 Jul 2007 12:31:42 -0000
***************
*** 717,722 ****
--- 717,734 ----
#endif
/*
+ * Open the relation. We call mdopen before mdnblocks, because that will
+ * fail if the first segment doesn't exist. That can happen in recovery,
+ * if the relation was dropped after the truncate.
+ */
+ v = mdopen(reln, InRecovery ? EXTENSION_RETURN_NULL : EXTENSION_FAIL);
+ if (v == NULL)
+ {
+ Assert(InRecovery);
+ return;
+ }
+
+ /*
* NOTE: mdnblocks makes sure we have opened all active segments, so
* that truncation loop will get them all!
*/
***************
*** 736,743 ****
if (nblocks == curnblk)
return; /* no work */
- v = mdopen(reln, EXTENSION_FAIL);
-
#ifndef LET_OS_MANAGE_FILESIZE
priorblocks = 0;
while (v != NULL)
--- 748,753 ----
Index: src/backend/storage/smgr/md.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/storage/smgr/md.c,v
retrieving revision 1.114.4.2
diff -c -r1.114.4.2 md.c
*** src/backend/storage/smgr/md.c 26 Apr 2007 23:25:30 -0000 1.114.4.2
--- src/backend/storage/smgr/md.c 20 Jul 2007 12:37:45 -0000
***************
*** 601,606 ****
--- 601,618 ----
#endif
/*
+ * Open the relation. We call mdopen before mdnblocks, because that will
+ * fail if the first segment doesn't exist. That can happen in recovery,
+ * if the relation was dropped after the truncate.
+ */
+ v = mdopen(reln, InRecovery);
+ if (v == NULL)
+ {
+ Assert(InRecovery);
+ return;
+ }
+
+ /*
* NOTE: mdnblocks makes sure we have opened all active segments, so
* that truncation loop will get them all!
*/
***************
*** 612,619 ****
if (nblocks == curnblk)
return nblocks; /* no work */
- v = mdopen(reln, false);
-
#ifndef LET_OS_MANAGE_FILESIZE
priorblocks = 0;
while (v != NULL)
--- 624,629 ----
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
