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Coalesce bug ?

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Hi,

In PostgreSQL 9.2, I have the following behavior, and I found it strange.

ps3 is executed or "never executed" ? !!!

JG

[postgres@]test=# create or replace function ps3(a int) returns int as $$ BEGIN
RAISE WARNING 'Call ps3(%)=%',$1,$1; RETURN $1::int;
END; $$ LANGUAGE plpgsql STRICT IMMUTABLE;
CREATE FUNCTION
Temps : 22,632 ms
[postgres@]test=# select coalesce( (select ps3(1)), (SELECT ps3(2)) );
WARNING:  Call ps3(1)=1
WARNING:  Call ps3(2)=2
 coalesce 
----------
        1
(1 ligne)

Temps : 0,692 ms
[postgres@]test=# select coalesce( ps3(1), ps3(2) );
WARNING:  Call ps3(1)=1
 coalesce 
----------
        1
(1 ligne)

Temps : 0,441 ms

[postgres@]test=# explain (analyze, verbose, buffers) select coalesce( (select ps3(1)), (SELECT ps3(2)) );
WARNING:  Call ps3(1)=1
WARNING:  Call ps3(2)=2
                                         QUERY PLAN                             
            
--------------------------------------------------------------------------------------------
 Result  (cost=0.02..0.03 rows=1 width=0) (actual time=0.006..0.006 rows=1 loops=1)
   Output: COALESCE($0, $1)
   InitPlan 1 (returns $0)
     ->  Result  (cost=0.00..0.01 rows=1 width=0) (actual time=0.001..0.001 rows=1 loops=1)
           Output: 1
   InitPlan 2 (returns $1)
     ->  Result  (cost=0.00..0.01 rows=1 width=0) (never executed)
           Output: 2
 Total runtime: 0.024 ms
(9 lignes)

Temps : 0,819 ms



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