From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mariel Cherkassky <mariel.cherkassky@gmail.com>
cc: =?UTF-8?Q?F=C3=A9lix_GERZAGUET?= <felix.gerzaguet@gmail.com>,
        pgsql-performance@lists.postgresql.org
Subject: Re: distinct on extract returns composite type
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Comments: In-reply-to Mariel Cherkassky <mariel.cherkassky@gmail.com>
	message dated "Mon, 30 Sep 2019 16:42:02 +0300"
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Date: Mon, 30 Sep 2019 09:48:16 -0400
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Mariel Cherkassky <mariel.cherkassky@gmail.com> writes:
> In my query I wrapped the columns with distinct : distinct (extract year...
> , extract quarter..).
> In your query you didnt wrap the columns with distinct but you just
> mentioned it. I guess this is the difference, thanks !

Yeah.  DISTINCT does not have an argument, it's just a keyword you
can stick in after SELECT.  So what you had as the select's targetlist
was (expr,expr), which is read as an implicit row constructor, that
is the same as ROW(expr,expr).  One of many arguably not-well-designed
things about SQL syntax :-(

			regards, tom lane