Horton

Re: Speedup twophase transactions

Nikhil Sontakke <nikhils@2ndquadrant.com>

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From: Nikhil Sontakke <nikhils@2ndquadrant.com>
To: Michael Paquier <michael.paquier@gmail.com>
Cc: David Steele <david@pgmasters.net>, Stas Kelvich <s.kelvich@postgrespro.ru>, Simon Riggs <simon@2ndquadrant.com>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>, Jesper Pedersen <jesper.pedersen@redhat.com>, Robert Haas <robertmhaas@gmail.com>
Date: 2017-03-17T07:42:44Z
Lists: pgsql-hackers 
>
> >
> > I don't think this will work. We cannot replace pg_twophase with shmem
> > entries + WAL pointers. This is because we cannot expect to have WAL
> entries
> > around for long running prepared queries which survive across
> checkpoints.
>
> But at the beginning of recovery, we can mark such entries with ondisk
> and inredo, in which case the WAL pointers stored in the shmem entries
> do not matter because the data is already on disk.
>

Ok, we can do that and then yes, RecoverPreparedTransaction() can just have
one loop going through the shmem entries. BUT, we cannot ignore
"inredo"+"ondisk" entries. For such entries, we will have to read and
recover from the corresponding 2PC files.

Regards,
Nikhils
-- 
 Nikhil Sontakke                   http://www.2ndQuadrant.com/
 PostgreSQL/Postgres-XL Development, 24x7 Support, 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