Re: [Patch] ALTER SYSTEM READ ONLY - Mailing list pgsql-hackers

From Michael Paquier
Subject Re: [Patch] ALTER SYSTEM READ ONLY
Date
Msg-id 20200626095921.GF1504@paquier.xyz
Whole thread Raw
In response to Re: [Patch] ALTER SYSTEM READ ONLY  (Amul Sul <sulamul@gmail.com>)
Responses Re: [Patch] ALTER SYSTEM READ ONLY  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On Fri, Jun 26, 2020 at 10:11:41AM +0530, Amul Sul wrote:
> I think that's expected since the server isn't clean shutdown, similar error can
> be seen with any server which has been shutdown in immediate mode
> (pg_clt -D data_dir -m i).

Any operation working on on-disk relation blocks needs to have a
consistent state, and a clean shutdown gives this guarantee thanks to
the shutdown checkpoint (see also pg_rewind).  There are two states in
the control file, shutdown for a primary and shutdown while in
recovery to cover that.  So if you stop the server cleanly but fail to
see a proper state with pg_checksums, it seems to me that the proposed
patch does not handle correctly the state of the cluster in the
control file at shutdown.  That's not good.
--
Michael

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