Re: Postgres does not use indexes with OR-conditions

On Fri, Nov 7, 2014 at 5:16 PM, arhipov <arhipov(at)dc(dot)baikal(dot)ru> wrote:

> Hello,
>
> I have just came across interesting Postgres behaviour with OR-conditions.
> Are there any chances that the optimizer will handle this situation in the
> future?
>
> select *
> from commons.financial_documents fd
> where fd.creation_time <= '2011-11-07 10:39:07.285022+08'
> order by fd.creation_time desc
> limit 200
>
> select *
> from commons.financial_documents fd
> where fd.creation_time = '2011-11-07 10:39:07.285022+08'
> or fd.creation_time < '2011-11-07 10:39:07.285022+08'
> order by fd.creation_time desc
> limit 200
>

It would certainly be possible, providing the constants compare equally,
but... Question: Would you really want to pay a, say 1% increase in
planning time for ALL queries, so that you could have this unique case of
queries perform better at execution time?

Is there a valid reason why you don't just write the query with the <=
operator?

Regards

David Rowley