Re: Slow query with indexed ORDER BY and LIMIT when using OR'd conditions - Mailing list pgsql-performance

johno <jan.suchal@gmail.com> writes:
> On Tue, Jul 22, 2014 at 4:53 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> johno <jan.suchal@gmail.com> writes:
>>> The obvious query is
>>> SELECT * FROM register_uz_accounting_entities
>>> WHERE effective_on > '2014-07-11' OR (effective_on = '2014-07-11' AND
>>> id > 1459)
>>> ORDER BY effective_on, id
>>> LIMIT 100

>> A more readily optimizable query is
>> SELECT * FROM register_uz_accounting_entities
>> WHERE (effective_on, id) > ('2014-07-11'::date, 1459)
>> ORDER BY effective_on, id
>> LIMIT 100

> Yes, but that query has completely different semantics - I can't change
> that.

No, it doesn't.  Read it again ... or read up on row comparisons,
if you're unfamiliar with that notation.  The above queries are
exactly equivalent per spec.

            regards, tom lane