Re: Postgres does not use indexes with OR-conditions

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От David Rowley
Тема Re: Postgres does not use indexes with OR-conditions
Дата
Msg-id CAApHDvr0X+eYy-bZJh-ch3Kr62BJkk=ZWACyndMKJsUBYWjQpg@mail.gmail.com
обсуждение исходный текст
Ответ на Postgres does not use indexes with OR-conditions  (arhipov <arhipov@dc.baikal.ru>)
Ответы Re: Postgres does not use indexes with OR-conditions
Список pgsql-performance
Дерево обсуждения
On Fri, Nov 7, 2014 at 5:16 PM, arhipov <arhipov@dc.baikal.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

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