Re: Understanding sequential versus index scans.
| От | Robert James |
|---|---|
| Тема | Re: Understanding sequential versus index scans. |
| Дата | |
| Msg-id | e09785e00907191710q7368d50fx2589b5005f49d7cf@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Understanding sequential versus index scans. (Tom Lane <tgl@sss.pgh.pa.us>) |
| Ответы |
Re: Understanding sequential versus index scans.
Re: Understanding sequential versus index scans. |
| Список | pgsql-general |
UNION was better, but still 5 times as slow as either query done individually.
set enable_seqscan=off didn't help at all - it was totally ignored
Is there anything else I can do?
On Sun, Jul 19, 2009 at 7:47 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Robert James <srobertjames@gmail.com> writes:It can use indexes for OR conditions, but not for arbitrary OR
> Hi. I notice that when I do a WHERE x, Postgres uses an index, and when I
> do WHERE y, it does so as well, but when I do WHERE x OR y, it
> doesn't.
conditions...... and that one is pretty arbitrary. You might have some luck with
> select * from dict
> where
> word in (select substr('moon', 0, generate_series(3,length('moon')))) --
> this is my X above
> OR word like 'moon%' -- this is my Y above
using a UNION instead, viz
select * from dict where X
union all
select * from dict where Y
regards, tom lane
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