From: | "Bossart, Nathan" <bossartn(at)amazon(dot)com> |
---|---|
To: | Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> |
Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, "Schneider (AWS), Jeremy" <schnjere(at)amazon(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: XMAX_LOCK_ONLY and XMAX_COMMITTED (fk/multixact code) |
Date: | 2022-01-06 21:55:25 |
Message-ID: | 0215C7B2-2505-4FCF-BFCE-E9964F1CC86A@amazon.com |
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Lists: | pgsql-hackers |
On 12/21/21, 11:42 AM, "Mark Dilger" <mark(dot)dilger(at)enterprisedb(dot)com> wrote:
> + /* pre-v9.3 lock-only bit pattern */
> + ereport(ERROR,
> + (errcode(ERRCODE_DATA_CORRUPTED),
> + errmsg_internal("found tuple with HEAP_XMAX_COMMITTED and"
> + "HEAP_XMAX_EXCL_LOCK set and "
> + "HEAP_XMAX_IS_MULTI unset")));
> + }
> +
>
> I find this bit hard to understand. Does the comment mean to suggest that the *upgrade* process should have eliminated all pre-v9.3 bit patterns, and therefore any such existing patterns are certainly corruption, or does it mean that data written by pre-v9.3 servers (and not subsequently updated) is defined as corrupt, or .... ?
>
> I am not complaining that the logic is wrong, just trying to wrap my head around what the comment means.
This is just another way that a tuple may be marked locked-only, and
we want to explicitly disallow locked-only + xmax-committed. This bit
pattern may be present on servers that were pg_upgraded from pre-v9.3
versions. See commits 0ac5ad5 and 74ebba8 for more detail.
Nathan
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