Re: Deparsing rewritten query

From: Julien Rouhaud <rjuju123(at)gmail(dot)com>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Gilles Darold <gilles(at)darold(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Deparsing rewritten query
Date: 2022-02-01 03:37:07
Message-ID: 20220201033707.facusnf6evjmnoo3@nol
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On Mon, Jan 31, 2022 at 10:05:44PM +0100, Pavel Stehule wrote:
> I don't feel good about forcing an alias. relname doesn't ensure
> uniqueness. You can have two views with the same name from different
> schemas. Moreover this field is necessary only when a deparsed query is
> printed, not always.

Yes I agree.

> Isn't possible to compute the correct subquery alias in print time when it
> is missing?

Actually I think that the current code already does everything to generate
unique refnames, it's just that they don't get printed for a query after view
expansions. I modified the patch to simply make sure that an alias is
displayed when it's a subquery and the output using a custom pg_get_query_def
is like that:

# select pg_get_query_def('select * from nsp1.v1');
FROM ( SELECT 1 AS nb) v1;+

(1 row)

# select pg_get_query_def('select * from nsp1.v1, nsp2.v1');
SELECT v1.nb, +
v1_1.nb +
FROM ( SELECT 1 AS nb) v1,+
( SELECT 1 AS nb) v1_1; +

(1 row)

Attachment Content-Type Size
v3-0001-Add-pg_get_query_def-to-deparse-and-print-a-rewri.patch text/plain 6.2 KB

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