Re: index used when casting to different type?

Ah.. This explains the performance I was getting with rserv, I have
int4 keys on my replicated tables and _rserv_log_ uses a text column
to be generic and support keys of different types. Problem is the
replicate function does a join from the text column to my key cast
as text and thus after running for a little bit, slows to a crawl.

Adding explicit text indexes on my int key columns seems to have
fixed the problem.

Thanks,

Alex.

On Mon, 19 Feb 2001, Tom Lane wrote:

> adb <adb(at)Beast(dot)COM> writes:
> > If I have a table with a key column stored as text and
> > another table with a key column stored as an int4 and
> > I join the two by casting the in4 column to text, will the existing
> > index on the int4 key be used?
>
> Nope. Indexes are associated with a particular datatype and only work
> for comparison operators of that datatype. The index on the first
> table's text column could possibly be used in this scenario, but not
> the one on the int4 column.
>
> regards, tom lane
>