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))


> 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

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