[EMAIL PROTECTED] writes:
> select * from t where c1 = 75000;
> select * from t where ((0 is null) OR (c1 = 75000));
> The first one properly uses the index on c1, the second does not.
> Obviously, a human looking at the second one would realize it's
> essentially identical to the first and properly evaluate the (0 is null)
> part once (since it's immutable) and then ignore it for the rest of the
> searching.
Well, you could update --- 8.2 contains code to recognize that the IS
NULL expression is constant, but prior releases do not.
However, if you're hoping to do this:
> ((vC1 IS NULL) OR (C1 = vC1)) AND
> ((vC2 IS NULL) OR (C2 = vC2)) ...
you're still gonna lose because those are variables not constants ...
regards, tom lane
---------------------------(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
