Re: Amcheck verification of GiST and GIN

[Tomas Vondra]

Hi,

I've spent a bit more time looking at the GiST part as part of my
"parallel GiST build" patch nearby, and I think there's some sort of
memory leak.

Consider this:

  create table t (a text);

  insert into t select md5(i::text)
    from generate_series(1,25000000) s(i);

  create index on t using gist (a gist_trgm_ops);

  select gist_index_check('t_a_idx', true);

This creates a ~4GB GiST trigram index, and then checks it. But that
gets killed, because of OOM killer. On my test machine it consumes
~6.5GB of memory before OOM intervenes.

The memory context stats look like this:

  TopPortalContext: 8192 total in 1 blocks; 7680 free (0 chunks); 512 used
    PortalContext: 1024 total in 1 blocks; 616 free (0 chunks); 408
used: <unnamed>
      ExecutorState: 8192 total in 1 blocks; 4024 free (4 chunks); 4168 used
        printtup: 8192 total in 1 blocks; 7952 free (0 chunks); 240 used
        ExprContext: 8192 total in 1 blocks; 7224 free (10 chunks); 968 used
          amcheck context: 3128950872 total in 376 blocks; 219392 free
(1044 chunks); 3128731480 used
            ExecutorState: 8192 total in 1 blocks; 7200 free (0 chunks);
992 used
              ExprContext: 8192 total in 1 blocks; 7952 free (0 chunks);
240 used
            GiST scan context: 22248 total in 2 blocks; 7808 free (8
chunks); 14440 used

This is from before the OOM kill, but it shows there's ~3GB of memory is
the amcheck context.

Seems like a memory leak to me - I didn't look at which place leaks.



regards

-- 
Tomas Vondra