Re: generic explain options v3 - RR Review

From: Andres Freund <andres(at)anarazel(dot)de>
To: pgsql-hackers(at)postgresql(dot)org
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>
Subject: Re: generic explain options v3 - RR Review
Date: 2009-07-19 01:15:38
Message-ID: 200907190315.39139.andres@anarazel.de
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Hi Robert, Hi All,

Patch applies with some offset changes, code changes look sensible, I
personally like the new syntax and the features it may allow in future. One,
possibly big, gripe remains though:
The formerly valid statement which cannot be written without the parentheses
and stay semantically equivalent:
EXPLAIN (SELECT 1 ORDER BY 1) UNION ALL (SELECT 2 ORDER BY 1);
is now not valid anymore (The added %prec UMINUS causes the first '(' to be
recognize as start of the option list as intended).
This currently can only be resolved by using an option list like:
EXPLAIN (VERBOSE OFF) ...
Its also currently impossible to use an empty set of parentheses to resolve
this - this could easily be changed though.

I have to admit I don't see a nice solution here except living with the
incompatibility... Perhaps somebody has a better idea?

Andres

PS: The 'offset corrected' version I tested with is attached

Attachment Content-Type Size
explain_options-v3_offset.patch text/x-patch 50.8 KB

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