From: | John Lumby <johnlumby(at)hotmail(dot)com> |
---|---|
To: | "pgsql-docs(at)lists(dot)postgresql(dot)org" <pgsql-docs(at)lists(dot)postgresql(dot)org> |
Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Subject: | Re: description of Aggregate Expressions |
Date: | 2019-12-06 20:01:14 |
Message-ID: | DM6PR06MB5562ED9060C811718CC59605A35F0@DM6PR06MB5562.namprd06.prod.outlook.com |
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Lists: | pgsql-admin pgsql-docs |
Tom Lane wrote
> > How about replacing "expression [ , ... ]" by "parameter_list" in the description,
> > and then stating that parameter_list can be either a single expression or ,
> > if the particular aggregate function accepts it (for which, consult that function's reference),
> > a comma-separated list of expressions.
>
> That's just as wrong. As we tried to explain before, the
> parenthesized-list syntax is a row constructor, so it only works
> in cases where the aggregate function can accept a composite
> argument type. Most don't.
>
But surely not *all* cases of a multi-expression parameter list of an aggregate function are row constructors are they? What about
select parent_id, name, GROUPING(parent_id , name), count(*) FROM mytable GROUP BY ROLLUP(parent_id , name);
In the piece "GROUPING(parent_id , name)" ,
is "(parent_id , name)" a row constructor or a list of two expressions?
Or are you saying those are one and the same thing?
Cheers, John
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