On 10/06/2015 01:48 PM, Oleksii Kliukin wrote:
On 06 Oct 2015, at 22:40, Adrian Klaver <adrian.klaver@xxxxxxxxxxx
<mailto:adrian.klaver@xxxxxxxxxxx>> wrote:
On 10/06/2015 01:13 PM, Oleksii Kliukin wrote:
Basically, if we invoke the first example, the foo table with have only
1 row and not 10, as supplied by the generate_series.
However, when ORDER BY is attached to the query, or aggregate (such as
max, min or array_agg) is wrapped around the test(id) call, the test
function is called exactly 10 times. If I replace the SELECT INTO with
PERFORM, it would also be called 10 times. Unfortunately, it is not
possible to use PERFORM directly in the CTE expression.
What CTE expression?
Any CTE expression :-). The example here is just an illustration to
expose the issue. The real-world query I came across used a complex CTE
expression and called a function at the end of it inside the SELECT INTO
statement.
Remember SELECT INTO inside plpgsql is different from SELECT INTO outside:
http://www.postgresql.org/docs/9.4/interactive/plpgsql-statements.html#PLPGSQL-STATEMENTS-SQL-ONEROW
"Tip: Note that this interpretation of SELECT with INTO is quite
different from PostgreSQL's regular SELECT INTO command, wherein the
INTO target is a newly created table. If you want to create a table from
a SELECT result inside a PL/pgSQL function, use the syntax CREATE TABLE
... AS SELECT.
So a simple CTE example might help clear things up.
How about:
DO $$
DECLARE l_id integer;
BEGIN
FOR l_id IN SELECT id
FROM generate_series(1,10) as id LOOP
SELECT INTO l_id test(l_id);
END LOOP;
END;
$$ LANGUAGE plpgsql;
This should work, but I'm interested in finding out why the original
statement behaves the way I’ve described.
Kind regards,
--
Oleksii
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
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