| From: | Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com> |
|---|---|
| To: | Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> |
| Cc: | Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Noah Misch <noah(at)leadboat(dot)com>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Aleksander Alekseev <aleksander(at)timescale(dot)com>, Postgres hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Maxim Orlov <orlovmg(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Greg Stark <stark(at)mit(dot)edu>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Peter Geoghegan <pg(at)bowt(dot)ie>, Maxim Orlov <m(dot)orlov(at)postgrespro(dot)ru>, lubennikovaav(at)gmail(dot)com |
| Subject: | Re: [PATCH] Improve amcheck to also check UNIQUE constraint in btree index. |
| Date: | 2024-05-17 19:42:42 |
| Message-ID: | CALT9ZEEJs33i2u_vGUFdubw7y_C92HPyNuwfS5uYS+71XmJEgw@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi, Mark!
On Fri, 17 May 2024 at 23:10, Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com>
wrote:
>
>
> > On May 17, 2024, at 11:51 AM, Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com>
> wrote:
> >
> > Amcheck with checkunique option does check uniqueness violation between
> pages. But it doesn't warranty detection of cross page uniqueness
> violations in extremely rare cases when the first equal index entry on the
> next page corresponds to tuple that is not visible (e.g. dead). In this, I
> followed the Peter's notion [1] that checking across a number of dead equal
> entries that could theoretically span even across many pages is an unneeded
> code complication and amcheck is not a tool that provides any warranty when
> checking an index.
>
> This confuses me a bit. The regression test creates a table and index but
> never performs any DELETE nor any UPDATE operations, so none of the index
> entries should be dead. If I am understanding you correct, I'd be forced
> to conclude that the uniqueness checking code is broken. Can you take a
> look?
>
At the first glance it's not clear to me:
- why your test creates cross-page unique constraint violations?
- how do you know they are not detected?
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