From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Andres Freund <andres@anarazel.de>
Cc: Alexandre Garcia <alexandre@vmfarms.com>
Cc: pgsql-admin@postgresql.org <pgsql-admin@postgresql.org>
Subject: Re: postgresql 9.6 - cannot freeze committed xmax
Date: Thu, 1 Mar 2018 14:40:10 -0300
Message-ID: <20180301174010.vqrjlps5stz6opzd@alvherre.pgsql> (raw)
In-Reply-To: <20180228234944.hjastb2mqr7rdnw5@alap3.anarazel.de>
Andres Freund wrote:
> Wonder if this a big enough fix? Isn't the bug "one layer up"? We
> shouldn't do the TransactionIdPrecedes() calls in the surrounding block,
> in the first place, right? Right now we could very well hit both
> ERROR: found xmax %u from before relfrozenxid %u
> and
> ERROR: cannot freeze committed xmax %u
> and freeze_xmax, totally_frozen will be wrong. I think that's largely
> harmless, but we should fix it nonetheless, and inspect other relevant
> sites.
Hmm ...
After reading the 9.2 code, I don't think so. These values must
absolutely be still within the freeze limits. The version pre-pgupgrade
should have replaced the xmax with InvalidTransactionId as soon as the
tuple was freezable.
In fact, I checked 9.2's code and heap_tuple_needs_freeze tests "if xmax
not a multi and < cutoff_xid"; and in that case heap_freeze_tuple does
change the value to 0.
I hope I'm not misunderstanding what you mean.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-admin@postgresql.org
Cc: alvherre@alvh.no-ip.org, andres@anarazel.de, alexandre@vmfarms.com
Subject: Re: postgresql 9.6 - cannot freeze committed xmax
In-Reply-To: <20180301174010.vqrjlps5stz6opzd@alvherre.pgsql>
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