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Re: Join Query Perfomance Issue

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Thomas Zaksek <zaksek(at)ptt(dot)uni-due(dot)de>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Join Query Perfomance Issue
Date: 2008-02-13 15:48:42
Message-ID: 15212.1202917722@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Thomas Zaksek <zaksek(at)ptt(dot)uni-due(dot)de> writes:
> Nested Loop Left Join  (cost=0.00..32604.48 rows=3204 width=14) (actual 
> time=11.991..2223.227 rows=2950 loops=1)
>    ->  Index Scan using 
> messungen_v_dat_2007_11_12_messpunkt_minute_tag_idx on 
> messungen_v_dat_2007_11_12 m  (cost=0.00..5371.09 rows=3204 width=4) 
> (actual time=0.152..12.385 rows=2950 loops=1)
>          Index Cond: ((ganglinientyp = 'M'::bpchar) AND (992 = minute_tag))
>    ->  Index Scan using messwerte_mv_nr_idx on messwerte_mv w  
> (cost=0.00..8.49 rows=1 width=18) (actual time=0.730..0.734 rows=1 
> loops=2950)
>          Index Cond: (w.nr = m.messpunkt)
>  Total runtime: 2234.143 ms
> (6 rows)

> To me this plan looks very clean and nearly optimal,

For so many rows I'm surprised it's not using a bitmap indexscan.
What PG version is this?  How big are these tables?

			regards, tom lane

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