From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Yotsunaga, Naoki <yotsunaga.naoki@jp.fujitsu.com>
Cc: Postgres hackers <pgsql-hackers@postgresql.org>
Subject: Re: automatic restore point
Date: Mon, 1 Oct 2018 19:06:32 -0300
Message-ID: <20181001220632.7a4jnzph2cwntq6w@alvherre.pgsql> (raw)
In-Reply-To: <544ca174-f0a1-fe75-ce74-3625fbc09447@2ndquadrant.com>
On 2018-Oct-01, Peter Eisentraut wrote:
> The following appears to work:
>
> CREATE FUNCTION evt_automatic_restart_point() RETURNS event_trigger
> LANGUAGE plpgsql
> AS $$
> BEGIN
> PERFORM pg_create_restore_point(tg_tag);
> END
> $$;
>
> CREATE EVENT TRIGGER automatic_restart_point ON ddl_command_start
> EXECUTE PROCEDURE evt_automatic_restart_point();
>
> Are there any concerns about this?
Mumble.
Re-reading the implementation in standard_ProcessUtility, I wonder what
is PROCESS_UTILITY_QUERY_NONATOMIC -- there seems to be a maze through
SPI that determines whether this flag is set or not, which could affect
whether the event trigger is useful. Are utilities executed through a
procedure detected by event triggers? If so, then this mechanism seems
good enough to me. But if there's a way to sneak utility commands (DROP
TABLE) without the event trigger being invoked, then no (and in that
case maybe it's just a bug in procedures and we can still not include
this patch).
(Grepping for "atomic" is unsurprisingly unhelpful. I really wish we
didn't use plain words as struct member names ...)
On the TRUNCATE case it's a bit annoying that you can't do it with event
triggers -- you have to create individual regular triggers on truncate
for each table (so you probably need yet another event trigger that
creates such triggers).
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: alvherre@2ndquadrant.com, peter.eisentraut@2ndquadrant.com, michael@paquier.xyz, yotsunaga.naoki@jp.fujitsu.com
Subject: Re: automatic restore point
In-Reply-To: <20181001220632.7a4jnzph2cwntq6w@alvherre.pgsql>
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