Re: function(contants) evaluated for every row - Mailing list pgsql-hackers

From pasman pasmański
Subject Re: function(contants) evaluated for every row
Date
Msg-id AANLkTi=9YJuaB7-qto9fTN74wak8FJA59P1wrSCn9-zg@mail.gmail.com
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In response to function(contants) evaluated for every row  (Bruce Momjian <bruce@momjian.us>)
Responses Re: function(contants) evaluated for every row
List pgsql-hackers
>I've seen this as well be a performance issue, in particular with partitioned tables.
>Out of habit I now write functions that always cache the value of the function in
>a variable and use the variable in the actual query to avoid this particular "gotcha".

subquery may be used to cache constants:

SELECT a_date FROM test WHERE a_date=(SELECT current_date);


"Seq Scan on test1  (cost=0.01..10.76 rows=5 width=4)"
"  Filter: (a_date = $0)"
"  InitPlan 1 (returns $0)"
"    ->  Result  (cost=0.00..0.01 rows=1 width=0)"


------------
pasman


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