| From: | Linos <info(at)linos(dot)es> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: unneeded joins on view |
| Date: | 2014-04-16 16:08:33 |
| Message-ID: | 534EAB01.80405@linos.es |
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| Lists: | pgsql-performance |
On 16/04/14 17:57, Heikki Linnakangas wrote:
> On 04/16/2014 06:13 PM, Linos wrote:
>> I thought that Postgresql would optimize out joins on columns I
>> don't ask for when I use the view but it doesn't, this query:
>
> It doesn't, because it would be wrong. It still has to check that the tables have a matching row (or multiple matching rows).
>
> If you use LEFT JOINs instead, and have a unique index on all the ID columns, then the planner can do what you expected and leave out the joins.
>
> - Heikki
>
>
You are right, I knew I was forgetting something important but I didn't know what was, thank you Heikki.
Regards,
Miguel Angel.
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