Re: Optimizer & boolean syntax

Using the famous WAG tech, in your first query the optimizer has to
evaluate monitored for each record to determine its value.

Robert Treat

On Thu, 2002-11-21 at 13:39, Daniele Orlandi wrote:
> 
> Are those two syntaxes eqivalent ?
> 
> select * from users where monitored;
> select * from users where monitored=true;
> 
> If the answer is yes, the optimimer probably doesn't agree with you :)
> 
> Tested on RC1:
> 
> template1=# create table a (a boolean, b text);
> CREATE TABLE
> 
> 
> .... inserted ~18000 rows with just one true (just to make an index scan 
>   meaningful)....
> 
> template1=# vacuum analyze a;
> VACUUM
> template1=# explain select * from a where a;
>                       QUERY PLAN
> ----------------------------------------------------
>   Seq Scan on a  (cost=0.00..802.64 rows=1 width=11)
>     Filter: a
> (2 rows)
> 
> template1=# explain select * from a where a=true;
>                            QUERY PLAN
> --------------------------------------------------------------
>   Index Scan using a_a on a  (cost=0.00..2.01 rows=1 width=11)
>     Index Cond: (a = true)
> (2 rows)
> 
> Bye!
> 
> -- 
>   Daniele Orlandi
>   Planet Srl
> 
> 
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