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From: =?ISO-8859-1?Q?C=E9dric_Villemain?= <cedric.villemain.debian@gmail.com>
Date: Thu, 27 May 2010 20:28:36 +0200
Message-ID: <AANLkTinuOUTbuke9FTMtwSObcZBio0uOS1ysWrqFyK3t@mail.gmail.com>
Subject: Re: Random Page Cost and Planner
To: David Jarvis <thangalin@gmail.com>
Cc: Bryan Hinton <bryan@bryanhinton.com>, pgsql-performance@postgresql.org
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2010/5/27 David Jarvis <thangalin@gmail.com>:
> Salut, C=E9dric.
>
>> I wonder what the plan will be if you replace sc.taken_* in :
>> m.taken BETWEEN sc.taken_start AND sc.taken_end
>> by values. It might help the planner...
>
> That is a fairly important restriction. I will try making it
> (year1||'-01-01')::date, but I have no constant value for it -- it is a
> user-supplied parameter. And then there's the year wrapping problem, too,
> where the ending year will differ from the starting year in certain cases=
.
> (Like querying rows between Dec 22, 1900 to Mar 22 1901 rather than Mar 2=
2
> 1900 to Dec 22 1900. The first query is the winter season and the second
> query is all seasons except winter.)

Ah, I though that you had a start and an end provided (so able to put
them in the query)

>
>>
>> Also, I'll consider explicit ordered join but I admit I haven't read
>> the whole thread (in particular the table size).
>
> C'est une grosse table. Pres que 40 million lines; il y a sept tableau co=
mme
> ca.
>
> I tried an explicit join in the past: it did not help much. But that was
> before everything was running this fast, so now that the system performs
> differently, maybe it will help?

yes. the documentation is fine for this topic :
http://www.postgresql.org/docs/8.4/interactive/explicit-joins.html
Consider the parameter to explicit join order (you can set it per sql sessi=
on).

You know your data and know what are the tables with less results to
join first.  ;)

>
> Dave
>
>


--=20
C=E9dric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support