On Mon, 30 Aug 2004, Martin Sarsale wrote:
> "Multicolumn indexes can only be used if the clauses involving the
> indexed columns are joined with AND. For instance,
>
> SELECT name FROM test2 WHERE major = constant OR minor = constant;
You can use DeMorgan's Theorem to transform an OR clause to an AND clause.
In general:
A OR B <=> NOT ((NOT A) AND (NOT B))
So:
> But I need something like:
>
> select * from t where c<>0 or d<>0;
select * from t where not (c=0 and d=0);
I haven't actually tried to see if postgresql would do anything
interesting after such a transformation.
---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
