Re: partitioned tables query not using indexes

From: A. Kretschmer
Subject: Re: partitioned tables query not using indexes
Date: ,
Msg-id: 20100224145536.GM22249@a-kretschmer.de
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In response to: partitioned tables query not using indexes  (Kevin Kempter)
Responses: Re: partitioned tables query not using indexes  (Kevin Kempter)
List: pgsql-performance

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partitioned tables query not using indexes  (Kevin Kempter, )
 Re: partitioned tables query not using indexes  ("A. Kretschmer", )
  Re: partitioned tables query not using indexes  (Kevin Kempter, )
 Re: partitioned tables query not using indexes  (Josh Berkus, )
  Re: partitioned tables query not using indexes  (Kenneth Marshall, )
   Re: partitioned tables query not using indexes  (Josh Berkus, )

In response to Kevin Kempter :
> Hi All;
>
> I have a table that has daily partitions.
>
> The check constraints look like this:
> CHECK (timezone('EST'::text, insert_dt) >= '2010-01-01'::date
> AND timezone('EST'::text, insert_dt) < '2010-01-02'::date)
>
> each partition has this index:
>     "fact_idx1_20100101_on_cust_id" btree (cust_id)
>
> If I run an explain hitting an individual partition I get an index scan:
>
> explain select distinct cust_id from children.fact_20100101;
>
>               QUERY PLAN
> --------------------------------------------------------------------------------------------------------------
>  Unique  (cost=0.00..136891.18 rows=70296 width=38)
>    ->  Index Scan using fact_idx1_20100101_on_cust_id on fact_20100101
> (cost=0.00..133112.0
>
>
>
>
>
> However the same query against the base table when specifying the check
> constraint key in the where clause produces sequential scans:

Have you set constraint_exclusion = on?



>
>
> explain  select distinct cust_id from fact
> where timezone('EST'::text, insert_dt) between  '2010-01-01'::date
> and '2010-01-02'::date;

Can you show the table definition? I'm not sure about the
timezone()-function and index...

Maybe you should try to rewrite your code to:

between  '2010-01-01 00:00'::timestamp and ...


Andreas
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Andreas Kretschmer
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