Jens Schipkowski a écrit :
On Wed, 13 Dec 2006 13:23:41 +0100, Arnaud Lesauvage <[EMAIL PROTECTED]>
Why is this query better than the other one ? Because it runs the
"(field IN ('some','other') AND field2 = 'Y')" once and then executes
the join with the resulting set ?
True. The Subselect in FROM clause will be executed once and will be
joined using the condition at where clause. So your condition at t2 is not
executed for each row in t1(2mio records) but for each row in t2(1k
records). And the boolean value is already set during update.
OK Jens, thanks for clarifying this.
I thought the planner could guess what to do in such cases.
Regards
--
Arnaud
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
