Re: extra function calls from query returning composite type - Mailing list pgsql-general

From Merlin Moncure
Subject Re: extra function calls from query returning composite type
Date
Msg-id CAHyXU0wHAtBJf8O6CBiUgp=8EnMVGCep=ZWWiXvYWR10v5p-sg@mail.gmail.com
Whole thread Raw
In response to extra function calls from query returning composite type  (Ronald Peterson <ron@hub.yellowbank.com>)
List pgsql-general
On Mon, Dec 29, 2014 at 9:06 AM, Ronald Peterson <ron@hub.yellowbank.com> wrote:
> I added a 'raise notice' to a plpgsql function I was working on
> recently, and noticed that my notification was being raised more often
> than I'd expect.  The notification is raised in a function ('getone'
> in my example below) that returns a single composite value.  This
> function is then called by another function ('getset') that returns a
> setof that composite value.  It appears that 'getone' is called once
> for each column of my composite type.  I whittled this down to the
> following example.
>
> I get the expected result from my query.  But it appears to me (and
> what do I know) that perhaps something inefficient is happening in the
> way this query is running.  Or maybe this is doing exactly what it
> should, in which case this is just a curiosity question - I don't
> understand why my 'getone' notice is called twice as often as I'd
> expect.

This was answered pretty clearly above.  The problem is (func()).*
syntax and how it's expanded in the query.  This was a longstanding
issue with set returning functions until 9.3 nailed it completely with
LATERAL.  Consider (func()).* to be deprecated syntax.

merlin


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