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Re: Amcheck verification of GiST and GIN

Tomas Vondra <tomas@vondra.me>

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From: Tomas Vondra <tomas@vondra.me>
To: "Andrey M. Borodin" <x4mmm@yandex-team.ru>, Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: Alexander Lakhin <exclusion@gmail.com>, Andrey Borodin <amborodin86@gmail.com>, Peter Geoghegan <pg@bowt.ie>, Mark Dilger <mark.dilger@enterprisedb.com>, Jose Arthur Benetasso Villanova <jose.arthur@gmail.com>, Andres Freund <andres@anarazel.de>, Nikolay Samokhvalov <samokhvalov@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-08-05T15:05:04Z
Lists: pgsql-hackers 
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

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. amcheck: Fix posting tree checks in gin_index_check()

  2. amcheck: Fix parent key check in gin_index_check()

  3. amcheck: Fix checks of entry order for GIN indexes

  4. amcheck: Remove unused GinScanItem->parentlsn field

  5. amcheck: Test gin_index_check on a multicolumn index

  6. Remove incidental md5() function use from test

  7. amcheck: Add a GIN index to the CREATE INDEX CONCURRENTLY tests

  8. amcheck: Add a test with GIN index on JSONB data

  9. amcheck: Fix indentation in verify_gin.c

  10. amcheck: Add gin_index_check() to verify GIN index

  11. amcheck: Move common routines into a separate module

  12. Fix grammar in GIN README

  13. Avoid amcheck inline compression false positives.