Query optimizer & prepared statements

   select ...
   from T
   where x > $1

prepare testy_prepare(int) as select * from T where x = $1;

execute testy_prepare(4);

Follow the docs :)
http://www.postgresql.org/docs/8.1/interactive/sql-prepare.html

--
Emanuel Calvo Franco
ArPUG [www.arpug.com.ar] / AOSUG Member
www.emanuelcalvofranco.com.ar

Jack Orenstein wrote:

If x is an integer column with an index, then

select ...
from T
where x > 1

and

select ...
from T
where x > 1000000000

could be optimized differently. So how is optimization done for a
prepared statement containing a variable, e.g.

select ...
from T
where x > $1

http://www.postgresql.org/docs/current/static/sql-prepare.html#AEN58703
explains this.

If your parameter is a unique key, then you won't see any difference. If
your parameter is a non-unique key, there may be differences depending
on your data/distribution etc.

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