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Re: Amcheck verification of GiST and GIN

Mark Dilger <mark.dilger@enterprisedb.com>

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From: Mark Dilger <mark.dilger@enterprisedb.com>
To: Kirill Reshke <reshkekirill@gmail.com>
Cc: Tomas Vondra <tomas@vondra.me>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>, Alexander Lakhin <exclusion@gmail.com>, Andrey Borodin <amborodin86@gmail.com>, Peter Geoghegan <pg@bowt.ie>, 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: 2025-02-28T18:31:29Z
Lists: pgsql-hackers 
> So, we have an entry tree page, where there is tuple on offset 80,
> with gin tuple category = 3, and then it goes category 0 again. And
> one more such pattern on the same page.
> The ginCompareEntries function compares the gin tuples category first.
> I do not understand how this would be a valid order on the page, given
> that
> ginCompareEntries used in `ginget.c` logic. . Maybe I'm missing
> something vital about GIN.
>

The only obvious definition of "wrong" for this is that gin index scans
return different result sets than table scans over the same data.  Using
your much smaller reproducible test case, and adding rows like:

SELECT COUNT(*) FROM tbl WHERE j @>
'"1129BBCABFFAACA9VGVKipnwohaccc9TSIMTOQKHmcGYVeFE_PWKLHmpyj60137672qugtsstugg"'::jsonb;
SELECT COUNT(*) FROM tbl WHERE j @> '{"": "r", "hji4124": "",
"HTJP_DAptxn6": 9}'::jsonb;
SELECT COUNT(*) FROM tbl WHERE j @> '[]'::jsonb;
SELECT COUNT(*) FROM tbl WHERE j @> NULL::jsonb;
SELECT COUNT(*) FROM tbl WHERE j @> '{"": -6, "__": [""], "YMb":
-22}'::jsonb;
SELECT COUNT(*) FROM tbl WHERE j @> '{"853": -60, "pjx": "",
"TGLUG_jxmrggv": null}'::jsonb;
SELECT COUNT(*) FROM tbl WHERE j @>
'"D3BDA069074174vx48A37IVHWVXLUP9382542ypsl1465pixtryzCBgrkkhrvCC_BDDFatkyXHLIe"'::jsonb;
SELECT COUNT(*) FROM tbl WHERE j @> '{"F18s": {"": -84194}, "ececab2":
[""]}'::jsonb;

The results are the same with or without the index.  Can you find any
examples where they differ?

—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.