postgresql.org@xxxxxxxxx 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
