From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | andrew(at)tao11(dot)riddles(dot)org(dot)uk |
Cc: | pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #7622: Incorrect aggregate level processing |
Date: | 2012-10-26 13:44:44 |
Message-ID: | 20677.1351259084@sss.pgh.pa.us |
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Lists: | pgsql-bugs |
andrew(at)tao11(dot)riddles(dot)org(dot)uk writes:
> select (select array_agg(random()*i) from (values (1),(2)) v(a)) from
> generate_series(1,3) i;
> Expected output is three rows each with a 2-element array; actual output
> is:
> ERROR: more than one row returned by a subquery used as an expression
> Looking at the explain, the aggregate is being pulled out of the subplan and
> evaluated at the top query level. (This came up while doing some random data
> generation, I've simplified it a bit.)
This is not a bug, it's the behavior required by SQL standard. An
aggregate belongs to the lowest query level supplying a variable to it
(except of course when it contains no variable at all). So it's
effectively an outer-reference constant for that inner select.
regards, tom lane
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