Hi,
Interesting idea.
With VOLATILE, the bug disappears.
With IMMUTABLE, the EXPLAIN and the execution does not match !!!!
That is a bug. Even if the behavior has to be different in VOLATILE and IMMUTABLE, the EXPLAIN and the execution MUST
becoherent.
JG
[postgres@]test=# create or replace function ps3(a int) returns int as $$ BEGIN
test$# RAISE WARNING 'Call ps3(%)=%',$1,$1; RETURN $1::int;
test$# END; $$ LANGUAGE plpgsql STRICT VOLATILE;
CREATE FUNCTION
Temps : 127,417 ms
[postgres@]test=# SELECT ps3(1);
WARNING: Call ps3(1)=1
ps3
-----
1
(1 ligne)
Temps : 0,941 ms
[postgres@]test=# SELECT ps3(2);
WARNING: Call ps3(2)=2
ps3
-----
2
(1 ligne)
Temps : 0,413 ms
[postgres@]test=# select coalesce( (select ps3(1)), (SELECT ps3(2)) );
WARNING: Call ps3(1)=1
coalesce
----------
1
(1 ligne)
Temps : 0,501 ms
[postgres@]test=# explain (verbose, analyze, buffers) select coalesce( (select ps3(1)), (SELECT ps3(2)) );
WARNING: Call ps3(1)=1
QUERY PLAN
--------------------------------------------------------------------------------
------------
Result (cost=0.52..0.53 rows=1 width=0) (actual time=0.072..0.072 rows=1 loops
=1)
Output: COALESCE($0, $1)
InitPlan 1 (returns $0)
-> Result (cost=0.00..0.26 rows=1 width=0) (actual time=0.067..0.067 rows
=1 loops=1)
Output: ps3(1)
InitPlan 2 (returns $1)
-> Result (cost=0.00..0.26 rows=1 width=0) (never executed)
Output: ps3(2)
Total runtime: 0.095 ms
(9 lignes)
Temps : 0,630 ms
[postgres@]test=# select coalesce( ps3(1), ps3(2) );
WARNING: Call ps3(1)=1
coalesce
----------
1
(1 ligne)
Temps : 0,451 ms
[postgres@]test=#