From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: pgsql-performance@postgresql.org
Subject: Re: partitioned tables query not using indexes
Date: Wed, 24 Feb 2010 15:55:36 +0100
Message-ID: <20100224145536.GM22249@a-kretschmer.de> (raw)
In-Reply-To: <201002240736.36341.kevink@consistentstate.com>
References: <201002240736.36341.kevink@consistentstate.com>
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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To: pgsql-performance@postgresql.org
Cc: andreas.kretschmer@schollglas.com
Subject: Re: partitioned tables query not using indexes
In-Reply-To: <20100224145536.GM22249@a-kretschmer.de>
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