Horton

Re: Speedup twophase transactions

Simon Riggs <simon@2ndquadrant.com>

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From: Simon Riggs <simon@2ndquadrant.com>
To: Nikhil Sontakke <nikhils@2ndquadrant.com>
Cc: Michael Paquier <michael.paquier@gmail.com>, Stas Kelvich <s.kelvich@postgrespro.ru>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>, Jesper Pedersen <jesper.pedersen@redhat.com>, Robert Haas <robertmhaas@gmail.com>
Date: 2017-01-27T10:07:46Z
Lists: pgsql-hackers 
On 27 January 2017 at 09:59, Nikhil Sontakke <nikhils@2ndquadrant.com> wrote:
>>> But, I put the recovery process and the checkpointer process of the
>>> standby under gdb with breakpoints on these functions, but both did
>>> not hit CreateRestartPoint() as well as CheckPointGuts() when I issued
>>> a promote :-|
>>
>> No end-of-recovery checkpoints happen at promotion since 9.3. You can
>> still use fallback_promote as promote file to trigger the pre-9.2 (9.2
>> included) behavior.
>
> Ok, so that means, we also need to fsync out these 2PC XIDs at promote
> time as well for their durability.

Why? The data files haven't been fsynced either at that point.

If there is a bug there it doesn't just affect 2PC.

What sequence of actions would cause data loss?

-- 
Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Speedup 2PC recovery by skipping two phase state files in normal path

  2. Add tests for two-phase commit

  3. Improve grammar of message about two-phase state files.

  4. Speedup 2PC by skipping two phase state files in normal path