Re: COMMIT NOWAIT Performance Option - Mailing list pgsql-hackers

From Zeugswetter Andreas ADI SD
Subject Re: COMMIT NOWAIT Performance Option
Date
Msg-id E1539E0ED7043848906A8FF995BDA57901CAFFBF@m0143.s-mxs.net
Whole thread Raw
In response to Re: COMMIT NOWAIT Performance Option  (Gregory Stark <stark@enterprisedb.com>)
Responses Re: COMMIT NOWAIT Performance Option  (Heikki Linnakangas <heikki@enterprisedb.com>)
List pgsql-hackers
> > Maybe a suitable replacement for full-page would be to sync the
first
> > WAL record for a page change before writing the buffer
>
> We *always* sync WAL records for page changes before writing
> the buffer for the page.

Um, is that so ? And how is that done ? (e.g. bgwriter would need to
wait for or even initiate a WAL record sync)
Seems this is not clear to others eighter.

Why else would people think we need a full data scan after crash without
full-pages ?
If this is true, all pages with possibly pending IO during crash will be
touched and could thus be checked during startup recovery.

I can see that we need to sync wal before write for certain changes, but
I don't see why we would currently need it for e.g. a heap insert, that
gets a free slot.

Andreas


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