Re: how to enforce index usage with +0

On Sun, Jun 10, 2007 at 05:32:55AM -0700, Timasmith wrote:
> select s.order_id
> from small_orders_table s, orders o
> where s.find_these_id in
> (select some_id from some_table where some_indexed_field = 'ABC')
> and s.order_id+0 = o.order_id
> and date_trunc('microseconds', o.valid_until_dt) < now()
>
> This should essentially use the s.some_indexed_field as the primary
> index and hit the orders table on the order id.

It will do this automatically if the selectivity of your
some_indexed_field values leans that way. I think you're probably
trying to outsmart the planner/optimiser here, and that's _usually_
not a good idea. IT shouldn't make any difference whether you add
that +0 or not, assuming the database is tuned correctly.

I'd be rather more worried about the date_trunc stuff. You probably
want a functional index on there.

A

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