Re: [HACKERS] Speedup twophase transactions - Mailing list pgsql-hackers

From Michael Paquier
Subject Re: [HACKERS] Speedup twophase transactions
Date
Msg-id CAB7nPqR-bpR=fPsmm0TQzmk7AKOYSq2Zs1yVY-jccTRqHsaz2w@mail.gmail.com
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In response to Re: [HACKERS] Speedup twophase transactions  (Simon Riggs <simon@2ndquadrant.com>)
Responses Re: [HACKERS] Speedup twophase transactions  (Nikhil Sontakke <nikhils@2ndquadrant.com>)
List pgsql-hackers
On Fri, Jan 27, 2017 at 8:23 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On 27 January 2017 at 11:01, Nikhil Sontakke <nikhils@2ndquadrant.com> wrote:
>> The xact_redo code will add prepared transactions to the
>> KnownPreparedList in memory. Earlier it used to create the on-disk 2PC
>> file.
>>
>> At standby promote, the surviving (yet uncommitted) prepared
>> transactions from KnownPreparedList need to be persisted, right?
>
> I don't see why, so please explain or show the error that can be
> caused if we don't.

I agree with Simon here. There is no point to fsync the 2PC files are
in case of an immediate crash after promotion replay will happen from
the last checkpoint, aka the one before the promotion has been
triggered. So there is no point to flush them at promotion, they would
be replayed anyway.
-- 
Michael



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