From: John Lumby <johnlumby@hotmail.com>
To: "pgsql-docs@lists.postgresql.org" <pgsql-docs@lists.postgresql.org>
Subject: description of  Aggregate Expressions
Thread-Topic: description of  Aggregate Expressions
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Date: Thu, 5 Dec 2019 22:18:42 +0000
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In PostgreSQL 12.1 Documentation chapter 4.2.7. Aggregate Expressions  it s=
ays=0A=
=0A=
=0A=
The syntax of an aggregate expression is one of the following:=0A=
  ... =0A=
aggregate_name (DISTINCT expression [ , ... ] [ order_by_clause ] ) [ FILTE=
R ( WHERE filter_clause ) ]=0A=
...=0A=
=0A=
I believe this is incorrect in the case where the DISTINCT is on a comma-se=
parated list of expressions.=0A=
It would imply that this is legal=0A=
=0A=
select count(DISTINCT parent_id , name) from  mytable=0A=
=0A=
but that is rejected with =0A=
ERROR:  function count(bigint, text) does not exist=0A=
=0A=
whereas =0A=
=0A=
select count(DISTINCT ( parent_id , name) ) from mytable=0A=
=0A=
is accepted.=0A=
=0A=
So I think to handle all cases the line in the doc should read=0A=
=0A=
aggregate_name (DISTINCT ( expression [ , ... ] ) [ order_by_clause ] ) [ F=
ILTER ( WHERE filter_clause ) ]=0A=
=0A=
I don't know how to indicate that those extra parentheses can be omitted if=
 the list has only one expression.=0A=
=0A=
Cheers,  John Lumby=