Re: [HACKERS] Bug? relpages, reltuples resets to zero

> I think the simple way of modifying the tuple in the page
> does not work. I found that catalog/index.c does the same for
> relpages and reltuples in UpdateStats(). Calling
> UpdateStats() after vc_updstats() as a quick hack solved the
> problem.

And now I know the way of modifying them in the buffer is the
only one to succeed. Doing it like index.c with
heap_replace() irritates vacuum itself.

Sometimes it's good to check returncodes :-).
WriteNoReleaseBuffer() (as it's name says) takes a buffer
number as argument, not a disk block number. Thus, it
returned FALSE sometimes when called to write buffer # 0.

The attdisbursion is also permanently saved on disk now. It
had the same problem.

Anyway, the fix is below.

Patch is regression tested.

Jan

--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me. #
#======================================== jwieck(at)debis(dot)com (Jan Wieck) #

*** vacuum.c.orig Fri Oct 23 16:47:21 1998
--- vacuum.c Fri Oct 23 16:41:56 1998
***************
*** 1792,1799 ****
--- 1792,1807 ----
/* overwrite the existing statistics in the tuple */
if (VacAttrStatsEqValid(stats))
{
+ Buffer abuffer;

+ /*
+ * We manipulate the heap tuple in the
+ * buffer, so we fetch it to get the
+ * buffer number
+ */
+ atup = heap_fetch(ad, SnapshotNow, &atup->t_ctid, &abuffer);
vc_setpagelock(ad, ItemPointerGetBlockNumber(&atup->t_ctid));
+ attp = (Form_pg_attribute) GETSTRUCT(atup);

if (stats->nonnull_cnt + stats->null_cnt == 0 ||
(stats->null_cnt <= 1 && stats->best_cnt == 1))
***************
*** 1822,1828 ****
if (selratio > 1.0)
selratio = 1.0;
attp->attdisbursion = selratio;
! WriteNoReleaseBuffer(ItemPointerGetBlockNumber(&atup->t_ctid));

/* DO PG_STATISTIC INSERTS */

--- 1830,1843 ----
if (selratio > 1.0)
selratio = 1.0;
attp->attdisbursion = selratio;
!
! /*
! * Invalidate the cache for the tuple
! * and write the buffer
! */
! RelationInvalidateHeapTuple(ad, atup);
! WriteNoReleaseBuffer(abuffer);
! ReleaseBuffer(abuffer);

/* DO PG_STATISTIC INSERTS */

***************
*** 1875,1884 ****
heap_close(sd);
}

RelationInvalidateHeapTuple(rd, rtup);

! /* XXX -- after write, should invalidate relcache in other backends */
! WriteBuffer(ItemPointerGetBlockNumber(&rtup->t_ctid));

heap_close(rd);
}
--- 1890,1904 ----
heap_close(sd);
}

+ /*
+ * Invalidate the cached pg_class tuple and
+ * write the buffer
+ */
RelationInvalidateHeapTuple(rd, rtup);

! WriteNoReleaseBuffer(buffer);
!
! ReleaseBuffer(buffer);

heap_close(rd);
}