Re: amcheck verification for GiST and GIN

On 29/07/2021 21:34, Nikolay Samokhvalov wrote:
> I was trying to check a bunch of GINs on some production after switching 
> from Ubuntu 16.04 to 18.04 and got many errors. So decided to check for 
> 16.04 first (that is still used on prod for that DB), without any 
> OS/glibc changes.
> 
> On 16.04, I still saw errors and it was not really expected because this 
> should mean that production is corrupted too. So, REINDEX should fix it. 
> But it didn't -- see output below. I cannot give data and thinking how 
> to create a synthetic demo of this. Any suggestions?
> 
> And is this a sign that the tool is wrong rather that we have a real 
> corruption cases? (I assume if we did, we would see no errors after 
> REINDEXing -- of course, if GIN itself doesn't have bugs).
> 
> Env: Ubuntu 16.04 (so, glibc 2.27), Postgres 12.7, patch from Heikki 
> slightly adjusted to work with PG12 (
> https://gitlab.com/postgres/postgres/-/merge_requests/5 
> <https://gitlab.com/postgres/postgres/-/merge_requests/5>) snippet used 
> to run amcheck:
> https://gitlab.com/-/snippets/2001962 
> <https://gitlab.com/-/snippets/2001962> (see file #3)

Almost certainly the tool is wrong. We went back and forth a few times 
with Pawel, fixing various bugs in the amcheck patch at this thread: 
https://www.postgresql.org/message-id/9fdbb584-1e10-6a55-ecc2-9ba8b5dca1cf%40iki.fi. 
Can you try again with the latest patch version from that thread, 
please? That's v5-0001-Amcheck-for-GIN-13stable.patch.

- Heikki