Thread: Problem with large tuples.
I've noticed that some of my tables with large text tuples have problem when these exceed some certain size. I know about the 8k tuplesize limit, but it seems the problem appears earlier than that. This is what I've been able to recreate: CREATE TABLE sizetest (id int, txt text); INSERT INTO sizetest (id, txt) VALUES (1, '...'); // ... = string of 4000 chars vacuum analyze; // <-- works nicely INSERT INTO sizetest (id, txt) VALUES (2, '...'); // ... = string of 4100 chars vacuum analyze; ERROR: Tuple is too big: size 8152, max size 8140 How come the insert works while the vacuum fails? Setup: Postgres 6.5.2, FreeBSD 3.3 /Patrik Kudo
Patrik Kudo writes:> I've noticed that some of my tables with large text tuples have> problem when these exceed some
certainsize. I know about the> 8k tuplesize limit, but it seems the problem appears earlier> than that. This is what
I'vebeen able to recreate:> > CREATE TABLE sizetest (id int, txt text);> INSERT INTO sizetest (id, txt) VALUES (1,
'...');// ... = string of> 4000 chars> vacuum analyze; // <-- works nicely> INSERT INTO sizetest (id, txt) VALUES (2,
'...');// ... = string of> 4100 chars> vacuum analyze;> ERROR: Tuple is too big: size 8152, max size 8140> > How come
theinsert works while the vacuum fails?
It's a bug. You need this patch against 6.5.3:
*** src/backend/commands/vacuum.c.orig Wed Aug 25 08:01:45 1999
--- src/backend/commands/vacuum.c Tue Jan 4 12:15:17 2000
***************
*** 2405,2414 **** stup = heap_formtuple(sd->rd_att, values, nulls); /*
----------------
! * insert the tuple in the relation and get the tuple's oid. *
---------------- */
! heap_insert(sd, stup); pfree(DatumGetPointer(values[3]));
pfree(DatumGetPointer(values[4])); pfree(stup);
--- 2405,2425 ---- stup = heap_formtuple(sd->rd_att, values, nulls); /*
----------------
! * Watch out for oversize tuple, which can happen if
! * both of the saved data values are long.
! * Our fallback strategy is just to not store the
! * pg_statistic tuple at all in that case. (We could
! * replace the values by NULLs and still store the
! * numeric stats, but presently selfuncs.c couldn't
! * do anything useful with that case anyway.) * ----------------
*/
! if (MAXALIGN(stup->t_len) <= MaxTupleSize)
! {
! /* OK to store tuple */
! heap_insert(sd, stup);
! }
! pfree(DatumGetPointer(values[3])); pfree(DatumGetPointer(values[4]));
pfree(stup);
After patching you should remove your statistics with
'DELETE FROM pg_statistic';
You might also need to patch vio.c. Get it from the latest snapshot...
Go back in the pgsql-bugs archive to read more about this problem. It
was discussed some weeks ago...
Dirk
Dirk Lutzebaeck wrote: > ... > You might also need to patch vio.c. Get it from the latest snapshot... vio.c? Can't find it the 6.5.3 sources. I guess that means I don't need to patch it, right? ;) /Palle
Palle Girgensohn <girgen@partitur.se> writes:
> Dirk Lutzebaeck wrote:
>> You might also need to patch vio.c. Get it from the latest snapshot...
> vio.c? Can't find it the 6.5.3 sources. I guess that means I don't need to patch it, right? ;)
I think he meant src/backend/access/heap/hio.c; there's a patch in there
that defends against adding an oversize tuple to a relation, IIRC.
regards, tom lane
Tom Lane wrote: > > I think he meant src/backend/access/heap/hio.c; there's a patch in there > that defends against adding an oversize tuple to a relation, IIRC. Thanks. I applied the patch. /Palle