From: Tom Lane <tgl@sss.pgh.pa.us>
To: Craig A. James <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: function not called if part of aggregate
Date: Sun, 11 Jun 2006 13:39:30 -0400
Message-ID: <18419.1150047570@sss.pgh.pa.us> (raw)
In-Reply-To: <448C505C.2080504@modgraph-usa.com>
References: <448C505C.2080504@modgraph-usa.com>
"Craig A. James" <cjames@modgraph-usa.com> writes:
> select count(1) from (select foo_init(value) from foo_init_table order by value_id) as foo;
> And indeed, it count() returns 800, as expected. But my function foo_init() never gets called!
Really? With the ORDER BY in there, it does get called, in my
experiments. What PG version is this exactly?
However, the short answer to your question is that PG does not guarantee
to evaluate parts of the query not needed to determine the result. You
could do something like
select count(x) from (select foo_init(value) as x from foo_init_table order by value_id) as foo;
to ensure that foo_init() must be evaluated.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, cjames@modgraph-usa.com
Subject: Re: function not called if part of aggregate
In-Reply-To: <18419.1150047570@sss.pgh.pa.us>
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