From: Tom Lane <tgl@sss.pgh.pa.us>
To: Philippe Lang <philippe.lang@attiksystem.ch>
Cc: pgsql-sql@postgresql.org
Subject: Re: function expression in FROM may not refer to other relations of same query level
Date: Thu, 12 Aug 2004 10:30:41 -0400
Message-ID: <28661.1092321041@sss.pgh.pa.us> (raw)
In-Reply-To: <6C0CF58A187DA5479245E0830AF84F420803B7@poweredge.attiksystem.ch>
References: <6C0CF58A187DA5479245E0830AF84F420803B7@poweredge.attiksystem.ch>
"Philippe Lang" <philippe.lang@attiksystem.ch> writes:
> I wish there was a way to run the query like this:
> select
> id,
> usr,
> code,
> CAST(get_lines(code) as lines)
> from tbl;
You can do something like this:
regression=# create type complex as (r float8, i float8);
CREATE TYPE
regression=# create function fooey(float8) returns complex as
regression-# 'select $1 + 1, $1 + 2' language sql;
CREATE FUNCTION
regression=# select f1, (fooey).r, (fooey).i from
regression-# (select f1, fooey(f1) as fooey from float8_tbl) ss;
f1 | r | i
-----------------------+-----------------------+-----------------------
0 | 1 | 2
-34.84 | -33.84 | -32.84
-1004.3 | -1003.3 | -1002.3
-1.2345678901234e+200 | -1.2345678901234e+200 | -1.2345678901234e+200
-1.2345678901234e-200 | 1 | 2
(5 rows)
Note the odd-looking parenthesization --- you can't write just "fooey.r"
because that looks like it should be a table and field name, not a field
name that is selected from.
If the sub-select is too simple, as it is in this case, the planner is
likely to "flatten out" the query into
select f1, (fooey(f1)).r, (fooey(f1)).i from float8_tbl;
thus defeating your purpose of not calling the function twice. The
currently best hack for preventing this is to add "OFFSET 0" to the
sub-select:
select f1, (fooey).r, (fooey).i from
(select f1, fooey(f1) as fooey from float8_tbl offset 0) ss;
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, philippe.lang@attiksystem.ch
Subject: Re: function expression in FROM may not refer to other relations of same query level
In-Reply-To: <28661.1092321041@sss.pgh.pa.us>
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