> "Pavan Deolasee" <[EMAIL PROTECTED]> writes:
>> The problem mentioned before is hard to reproduce with the
>> suggested change, but its not completely gone away. I have
>> seen that again on CVS HEAD with the patch applied.
>> I am facing another issue with VACUUM FULL. This
>> problem gets reproduced with HOT very easily, but takes
>> few attempts to reproduce with CVS HEAD, but it
>> certainly exists.
I've developed the attached patch against HEAD, and no longer see any
funny behavior. Would appreciate it if you'd test some more, though.
regards, tom lane
Index: vacuum.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/commands/vacuum.c,v
retrieving revision 1.348
diff -c -r1.348 vacuum.c
*** vacuum.c 13 Mar 2007 00:33:40 -0000 1.348
--- vacuum.c 13 Mar 2007 18:00:14 -0000
***************
*** 1880,1885 ****
--- 1880,1894 ----
* To be on the safe side, we abandon the repair_frag
process if
* we cannot find the parent tuple in vtlinks. This
may be overly
* conservative; AFAICS it would be safe to move the
chain.
+ *
+ * Also, because we distinguish DEAD and RECENTLY_DEAD
tuples
+ * using OldestXmin, which is a rather coarse test, it
is quite
+ * possible to have an update chain in which a tuple we
think is
+ * RECENTLY_DEAD links forward to one that is
definitely DEAD.
+ * In such a case the RECENTLY_DEAD tuple must actually
be dead,
+ * but it seems too complicated to try to make VACUUM
remove it.
+ * We treat each contiguous set of RECENTLY_DEAD tuples
as a
+ * separately movable chain, ignoring any intervening
DEAD ones.
*/
if (((tuple.t_data->t_infomask & HEAP_UPDATED) &&
!TransactionIdPrecedes(HeapTupleHeaderGetXmin(tuple.t_data),
***************
*** 1892,1897 ****
--- 1901,1907 ----
Buffer Cbuf = buf;
bool freeCbuf = false;
bool chain_move_failed = false;
+ bool moved_target = false;
ItemPointerData Ctid;
HeapTupleData tp = tuple;
Size tlen = tuple_len;
***************
*** 1919,1925 ****
* If this tuple is in the begin/middle of the
chain then we
* have to move to the end of chain. As with
any t_ctid
* chase, we have to verify that each new tuple
is really the
! * descendant of the tuple we came from.
*/
while (!(tp.t_data->t_infomask &
(HEAP_XMAX_INVALID |
HEAP_IS_LOCKED)) &&
--- 1929,1941 ----
* If this tuple is in the begin/middle of the
chain then we
* have to move to the end of chain. As with
any t_ctid
* chase, we have to verify that each new tuple
is really the
! * descendant of the tuple we came from;
however, here we
! * need even more than the normal amount of
paranoia.
! * If t_ctid links forward to a tuple
determined to be DEAD,
! * then depending on where that tuple is, it
might already
! * have been removed, and perhaps even replaced
by a MOVED_IN
! * tuple. We don't want to include any DEAD
tuples in the
! * chain, so we have to recheck
HeapTupleSatisfiesVacuum.
*/
while (!(tp.t_data->t_infomask &
(HEAP_XMAX_INVALID |
HEAP_IS_LOCKED)) &&
***************
*** 1933,1938 ****
--- 1949,1955 ----
OffsetNumber nextOffnum;
ItemId nextItemid;
HeapTupleHeader nextTdata;
+ HTSV_Result nextTstatus;
nextTid = tp.t_data->t_ctid;
priorXmax =
HeapTupleHeaderGetXmax(tp.t_data);
***************
*** 1963,1968 ****
--- 1980,1998 ----
ReleaseBuffer(nextBuf);
break;
}
+ /* must check for DEAD or MOVED_IN
tuple, too */
+ nextTstatus =
HeapTupleSatisfiesVacuum(nextTdata,
+
OldestXmin,
+
nextBuf);
+ if (nextTstatus == HEAPTUPLE_DEAD ||
+ nextTstatus ==
HEAPTUPLE_INSERT_IN_PROGRESS)
+ {
+ ReleaseBuffer(nextBuf);
+ break;
+ }
+ /* if it's MOVED_OFF we shoulda moved
this one with it */
+ if (nextTstatus ==
HEAPTUPLE_DELETE_IN_PROGRESS)
+ elog(ERROR, "updated tuple is
already HEAP_MOVED_OFF");
/* OK, switch our attention to the next
tuple in chain */
tp.t_data = nextTdata;
tp.t_self = nextTid;
***************
*** 2034,2039 ****
--- 2064,2074 ----
free_vtmove--;
num_vtmove++;
+ /* Remember if we reached the original
target tuple */
+ if
(ItemPointerGetBlockNumber(&tp.t_self) == blkno &&
+
ItemPointerGetOffsetNumber(&tp.t_self) == offnum)
+ moved_target = true;
+
/* Done if at beginning of chain */
if (!(tp.t_data->t_infomask &
HEAP_UPDATED) ||
TransactionIdPrecedes(HeapTupleHeaderGetXmin(tp.t_data),
***************
*** 2102,2107 ****
--- 2137,2149 ----
ReleaseBuffer(Cbuf);
freeCbuf = false;
+ /* Double-check that we will move the current
target tuple */
+ if (!moved_target && !chain_move_failed)
+ {
+ elog(DEBUG2, "failed to chain back to
target --- cannot continue repair_frag");
+ chain_move_failed = true;
+ }
+
if (chain_move_failed)
{
/*
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