| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Michael Paquier <michael(at)paquier(dot)xyz> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: finding changed blocks using WAL scanning |
| Date: | 2019-04-22 16:04:01 |
| Message-ID: | CA+TgmobHRgOOHxiWNS4sa3wuooPVmVtmg6U0NR=TmWTqT_w1MA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, Apr 21, 2019 at 10:21 PM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> If you create the extra file when a segment is finished and we switch
> to a new one, then the extra work would happen for a random backend,
> and it is going to be more costly to scan a 1GB segment than a 16MB
> segment as a one-time operation, and less backends would see a
> slowdown at equal WAL data generated. From what I can see, you are
> not planning to do such operations when a segment finishes being
> written, which would be much better.
Well, my plan was to do it all from a background worker, so I do not
think a random backend would ever have to do any extra work.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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