| From: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru>, Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Subject: | Re: logical decoding of two-phase transactions |
| Date: | 2017-02-01 20:15:55 |
| Message-ID: | 589241FB.8060509@postgrespro.ru |
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| Lists: | pgsql-hackers |
On 02/01/2017 10:32 PM, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> Also, including the GID in the WAL for each COMMIT/ABORT PREPARED
>> doesn't seem inordinately expensive to me.
> I'm confused ... isn't it there already? If not, how do we handle
> reconstructing 2PC state from WAL at all?
>
> regards, tom lane
>
>
Right now logical decoding ignores prepare and take in account only "commit prepared":
/*
* Currently decoding ignores PREPARE TRANSACTION and will just
* decode the transaction when the COMMIT PREPARED is sent or
* throw away the transaction's contents when a ROLLBACK PREPARED
* is received. In the future we could add code to expose prepared
* transactions in the changestream allowing for a kind of
* distributed 2PC.
*/
For some scenarios it works well, but if we really need prepared state at replica (as in case of multimaster), then it is not enough.
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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