Re: Index usage in bitwise operation context

"W.Alphonse HAROUNY" <wharouny(at)gmail(dot)com> writes:

> Question:
> --------------
> I have an SQL request similar to:
>
> SELECT ..... FROM TBL1, TBL2 WHERE
> <inner join between TBL1 and TBL2 is True> AND
> TBL1.CATEGORY & TBL2.CATEGORY <> 0 //-- where & is the AND bitwise
> operator
>
> Qst:
> 1/ IS the above SQL request will use the INDEX [categoryGroup] defined on
> TBL1 and TBL2 ?

No, & isn't an indexable operator for any of the standard indexing methods.

You could create 32 partial indexes on some other key with clauses like
WHERE tbl1.category & 0100... = 0100...
But I don't think that would be useful for a join clause in any case.

Second idea, you could create an expression index on

tbl1 (category & 0100... = 0100...,
category & 0010... = 0010...,
category & 0001... = 0001...,
...)

Again I don't see that it's going to be used for a join condition.

Lastly, you could look for a GIST index method for varbit which would be
superior to both of the above tactics. I'm still not sure it would be able to
handle a join clause though, but maybe?

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com