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From: Peter Geoghegan <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: BTree index corruption (heap-tid-past-end, unexpected zero page, misplaced TID in posting list) recurring on high-churn tables, PG 18.3, data_checksums=on, no preceding crash
Date: Thu, 2 Jul 2026 14:32:31 -0400
Message-ID: <CAH2-Wzmocfze4XEk=XP6wCdo8kWbnJUsBoJW3RG-Jq=nP16bmQ@mail.gmail.com> (raw)
In-Reply-To: <CAFDALapqu1NLj-svUV-sPdLs-e0DMEiaoS-kTFXhUqtjqn7M=A@mail.gmail.com>
References: <CAFDALapqu1NLj-svUV-sPdLs-e0DMEiaoS-kTFXhUqtjqn7M=A@mail.gmail.com>

On Thu, Jul 2, 2026 at 2:25 PM Alessandro Regolini
<[email protected]> wrote:
> What we can provide on the next occurrence
> ------------------------------------------
> We run a periodic amcheck sweep, so we usually catch a fresh case before
> reindexing. Before REINDEX we can capture, for the affected block:
>   - contrib/pageinspect: bt_page_items() of the index block and
>     heap_page_items() / page_header() of the referenced heap block
>   - full bt_index_check / bt_index_parent_check output
>   - verify_heapam() of the underlying table
> Please tell us which dumps would be most useful to root-cause this (btree
> deduplication / VACUUM interaction is our current suspicion).

Those all seem useful, but I doubt that bt_index_parent_check is going
to add much over bt_index_check. However, you should be sure to run
bt_index_check with heapallindexed=true, which will verify agreement
between the index and the underlying table.

If you see a heapallindexed=true failure, getting page images for the
pointed-to heap page is useful (as well as the index page). I prefer a
raw dump of the page itself over a textual representation. See the
procedure here:

https://wiki.postgresql.org/wiki/Getting_a_stack_trace_of_a_running_PostgreSQL_backend_on_Linux/BSD#...

-- 
Peter Geoghegan

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  Subject: Re: BTree index corruption (heap-tid-past-end, unexpected zero page, misplaced TID in posting list) recurring on high-churn tables, PG 18.3, data_checksums=on, no preceding crash
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