| From: | Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> |
|---|---|
| To: | Pavel Borisov <pashkin(dot)elfe(at)gmail(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 19:10:10 |
| Message-ID: | 28FCD9E5-795E-44F4-ADFA-DBCAC1945DA1@enterprisedb.com |
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| Lists: | pgsql-hackers |
> 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?
—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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