From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
---|---|
To: | Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)bowt(dot)ie> |
Subject: | Re: room for improvement in amcheck btree checking? |
Date: | 2020-12-01 23:26:53 |
Message-ID: | 20201201232653.GA5727@alvherre.pgsql |
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Lists: | pgsql-hackers |
On 2020-Dec-01, Mark Dilger wrote:
> 7) Run a SQL query that uses an index scan on the table and see that it errors with something like:
>
> ERROR: could not read block 0 in file "base/13097/16391": read only 0 of 8192 bytes
>
> I found it surprising that even when precisely zero of the tids in the
> index exist in the table the index checks all come back clean.
Yeah, I've seen this kind of symptom in production databases (indexes
pointing to non-existant heap pages).
I think one useful cross-check that amcheck could do, is verify that if
a heap page is referenced from the index, then the heap page must exist.
Otherwise, it's a future index corruption of sorts: the old index
entries will point to the wrong new heap tuples as soon as the table
grows again.
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