Re: BUG #17485: Records missing from Primary Key index when doing REINDEX INDEX CONCURRENTLY

> On 24 May 2022, at 23:15, Andres Freund <andres@anarazel.de> wrote:
>
> With fsync=on, it's much harder to reproduce.
That exaplains why it's easier to reproduce on MacOS: it seem it ignores fsync.



> On 24 May 2022, at 23:15, Andres Freund <andres@anarazel.de> wrote:
>
> I suspect the problem might be related to pruning done during the validation
> scan. Once PROC_IN_SAFE_IC is set, the backend itself will not preserve tids
> its own snapshot might need. Which will wreak havoc during the validation
> scan.

I observe that removing PROC_IN_SAFE_IC for index_validate() fixes tests.
But why it's not a problem for index_build() scan?

And I do not understand why it's a problem that tuple is pruned during the scan... How does this "wreak havoc" happen?

Best regards, Andrey Borodin.