| From: | Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru> |
|---|---|
| To: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Subject: | Re: logical decoding of two-phase transactions |
| Date: | 2017-01-26 11:34:47 |
| Message-ID: | 3477E635-F590-4432-BD20-C59142B65CD3@postgrespro.ru |
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| Lists: | pgsql-hackers |
> On 26 Jan 2017, at 12:51, Craig Ringer <craig(at)2ndquadrant(dot)com> wrote:
>
> * Tracking xid/gid map in memory also doesn’t help much — if server reboots between prepare
> and commit we’ll lose that mapping.
>
> Er what? That's why I suggested using the prepared xacts shmem state. It's persistent as you know from your work on prepared transaction files. It has all the required info.
Imagine following scenario:
1. PREPARE happend
2. PREPARE decoded and sent where it should be sent
3. We got all responses from participating nodes and issuing COMMIT/ABORT
4. COMMIT/ABORT decoded and sent
After step 3 there is no more memory state associated with that prepared tx, so if will fail
between 3 and 4 then we can’t know GID unless we wrote it commit record (or table).
--
Stas Kelvich
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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