Re: totally different plan when using partitions

From: Scara Maccai <m_lists(at)yahoo(dot)it>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: totally different plan when using partitions
Date: 2009-08-14 07:43:32
Message-ID: 930905.3109.qm@web24613.mail.ird.yahoo.com
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Query:
set enable_mergejoin=off;set enable_hashjoin=off;

explain analyze
select nome1,
thv3tralacc,
dltbfpgpdch
FROM cell_bsc_60_0610 as cell_bsc
left outer join teststscell73_test as data on data.ne_id=cell_bsc.nome1
left outer join teststscell13_test as data1 on data1.ne_id=cell_bsc.nome1 and data1.time=data.time
where

data.time >=cell_bsc.starttime and data.time <=cell_bsc.endtime and
data.time between '2006-10-01 00:00:00' and '2006-10-02 01:00:00'
and data1.time >=cell_bsc.starttime and data1.time <=cell_bsc.endtime
and data1.time between '2006-10-01 00:00:00' and '2006-10-02 01:00:00'
and cell_bsc.nome2=2;

Explain analyze on my sistem ("PostgreSQL 8.4.0 on sparc-sun-solaris2.10, compiled by cc: Sun C 5.9 SunOS_sparc Patch 124867-02 2007/11/27, 64-bit"):

http://explain-analyze.info/query_plans/3822-query-plan-2528

interesting bit (if I got it right):

-> Nested Loop (cost=0.0..3139.65 rows=6531 width=36) (actual time=0.141..13.459 rows=3692 loops=1)
Join Filter: ((data1.time >= cell_bsc.starttime) AND (data1.time <= cell_bsc.endtime) AND (cell_bsc.nome1 = data1.ne_id))
-> Seq Scan on cell_bsc_60_0610 cell_bsc (cost=0.0..99.39 rows=285 width=20) (actual time=0.033..1.740 rows=285 loops=1)
Filter: (nome2 = 2)
-> Append (cost=0.0..10.6 rows=4 width=16) (actual time=0.012..0.027 rows=13 loops=285)

285*4 should give 1140 max, not 6531: is this different enough?

If it is, I have a 585K dump file that should recreate the problem.

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