Re: Default gucs for EXPLAIN

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Guillaume Lelarge <guillaume(at)lelarge(dot)info>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Bruce Momjian <bruce(at)momjian(dot)us>, Nikolay Samokhvalov <samokhvalov(at)gmail(dot)com>, Vik Fearing <vik(at)postgresfriends(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Default gucs for EXPLAIN
Date: 2020-05-26 14:25:15
Message-ID: 20200526142515.GE3418@tamriel.snowman.net
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Greetings,

* Guillaume Lelarge (guillaume(at)lelarge(dot)info) wrote:
> Le mar. 26 mai 2020 à 04:27, Stephen Frost <sfrost(at)snowman(dot)net> a écrit :
> > To that end- what if this was done client-side with '\explain' or
> > similar? Basically, it'd work like \watch or \g but we'd have options
> > under pset like "explain_analyze t/f" and such. I feel like that'd also
> > largely address the concerns about how this might 'feature creep' to
> > other commands- because those other commands don't work with a query
> > buffer, so it wouldn't really make sense for them.
> >
> > As for the concerns wrt explain UPDATE or explain DETELE actually
> > running the query, that's what transactions are for, and if you don't
> > feel comfortable using transactions or using these options- then don't.
>
> This means you'll always have to check if the new GUCs are set up in a way
> it will actually execute the query or to open a transaction for the same
> reason. This is a huge behaviour change where people might lose data.

It's only a behaviour change if you enable it.. and the suggestion I
made specifically wouldn't even be a regular 'explain', you'd be using
'\explain' in psql, a new command.

> I really don't like this proposal (the new GUCs).

The proposal you're commenting on (seemingly mine, anyway) didn't
include adding any new GUCs.

Thanks,

Stephen

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