Re: [PATCH] Hooks at XactCommand level

Le 01/07/2021 à 18:47, Tom Lane a écrit :
> Nicolas CHAHWEKILIAN <leptitstagiaire(at)gmail(dot)com> writes:
>> As far as I am concerned, I am totally awaiting for this kind of feature
>> exposed here, for one single reason at this time : the extension
>> pg_statement_rollback will be much more valuable with the ability of
>> processing "rollback to savepoint" without the need for explicit
>> instruction from client side (and this patch is giving this option).
> What exactly do these hooks do that isn't done as well or better
> by the RegisterXactCallback and RegisterSubXactCallback mechanisms?
> Perhaps we need to define some additional event types for those?
> Or pass more data to the callback functions?
>
> I quite dislike inventing a hook that's defined as "run during
> start_xact_command", because there is basically nothing that's
> not ad-hoc about that function: it's internal to postgres.c
> and both its responsibilities and its call sites have changed
> over time. I think anyone hooking into that will be displeased
> by the stability of their results.

Sorry Tom, it seems that I have totally misinterpreted your comments,
google translate was not a great help for my understanding but Julien
was. Thanks Julien.

I'm joining a new patch v4 that removes the need of any hook and adds a
new events XACT_EVENT_COMMAND_START and SUBXACT_EVENT_COMMAND_START that
can be cautch in the xact callbacks when a new command is to be executed.

--
Gilles Darold
http://www.darold.net/