public inbox for [email protected]
help / color / mirror / Atom feedFrom: Alvaro Herrera <[email protected]>
To: Fujii Masao <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Petr Jelinek <[email protected]>
Cc: [email protected]
Cc: pgsql-docs <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: [DOCS] max_worker_processes on the standby
Date: Fri, 4 Dec 2015 12:56:16 -0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAHGQGwFRDStn0jBS5GH_JwD-_PD+_tBe+yxFs5cq6LFxyLQ+bw@mail.gmail.com>
References: <CA+Tgmoaqmo-eSyBQu996Lko7AWu-Yij-Tjd1Zi-LM3UJmU2MKQ@mail.gmail.com>
<[email protected]>
<CA+Tgmob_NQhUgbDCFEWBy6CanVG7mo5FuzPGR1_q9=7Gv+Q0cw@mail.gmail.com>
<[email protected]>
<CA+TgmoYNUAt-7fJboXGOVcXmS_OeddhL+r5Tq3qDebdhJHR8mA@mail.gmail.com>
<[email protected]>
<[email protected]>
<CAHGQGwEsKDoYFarJjQ4dvH2ZiDxxK0ZcBP4cV2ahdje5pRW2JA@mail.gmail.com>
<[email protected]>
<CAHGQGwFRDStn0jBS5GH_JwD-_PD+_tBe+yxFs5cq6LFxyLQ+bw@mail.gmail.com>
List-Unsubscribe: <mailto:[email protected]?body=unsub%20pgsql-hackers>
Fujii Masao wrote:
> Sorry for not reviewing the patch before you push it...
>
> In HEAD, I ran very simple test case:
>
> 1. enable track_commit_timestamp
> 2. start the server
> 3. run some transactions
> 4. execute pg_last_committed_xact() -- returns non-null values
> 5. shutdown the server with immdiate mode
> 6. restart the server -- crash recovery happens
> 7. execute pg_last_committed_xact()
>
> The last call of pg_last_committed_xact() returns NULL values, which means
> that the xid and timestamp information of the last committed transaction
> disappeared by crash recovery. Isn't this a bug?
Hm, not really, because the status of the "last" transaction is kept in
shared memory as a cache and not expected to live across a restart.
However, I tested the equivalent scenario:
alvherre=# create table fg();
CREATE TABLE
alvherre=# select ts.* from pg_class,pg_xact_commit_timestamp(xmin) ts where relname = 'fg';
ts
-------------------------------
2015-12-04 12:41:48.017976-03
(1 fila)
then crash the server, and after recovery the data is gone:
alvherre=# select ts.*, xmin, c.relname from pg_class c,pg_xact_commit_timestamp(xmin) ts where relname = 'fg';
ts | xmin | relname
----+------+---------
| 630 | fg
(1 fila)
Not sure what is going on; my reading of the code certainly says that
the data should be there. I'm looking into it.
I also noticed that I didn't actually push the whole of the patch
yesterday -- I neglected to "git add" the latest changes, the ones that
fix the promotion scenario :-( so the commit messages is misleading
because it describes something that's not there.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
--
Sent via pgsql-hackers mailing list ([email protected])
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
view thread (38+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: [DOCS] max_worker_processes on the standby
In-Reply-To: <[email protected]>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox