| From: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
|---|---|
| To: | Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com> |
| Cc: | Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: logical decoding of two-phase transactions |
| Date: | 2017-03-16 11:44:36 |
| Message-ID: | CAMsr+YHb8gTViN3feVJFO2DrVrjVtWjESqhBHfpnssTWwf+GQg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 15 March 2017 at 15:42, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com> wrote:
> Thinking about this some more. Why can't we use the same mechanism
> standby uses, ie, use xid to identify the 2PC?
It pushes work onto the downstream, which has to keep an <xid,gid>
mapping in a crash-safe, persistent form. We'll be doing a flush of
some kind anyway so we can report successful prepare to the upstream
so an additional flush of a SLRU might not be so bad for a postgres
downstream. And I guess any other clients will have some kind of
downstream persistent mapping to use.
So I think I have a mild preference for recording the gid on 2pc
commit and abort records in the master's WAL, where it's very cheap
and simple.
But I agree that just sending the xid is a viable option if that falls through.
I'm going to try to pick this patch up and amend its interface per our
discussion earlier, see if I can get it committable.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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