Re: Inner Join of the same table

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: sebaioni-postgresql(at)yahoo(dot)com(dot)ar
Cc: Performance PostgreSQL <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Inner Join of the same table
Date: 2006-08-15 21:13:02
Message-ID: 20384.1155676382@sss.pgh.pa.us
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=?iso-8859-1?q?Sebasti=E1n=20Baioni?= <sebaioni-postgresql(at)yahoo(dot)com(dot)ar> writes:
> 8 -> GroupAggregate (cost=0.00..37348395.05 rows=3951 width=25) (actual
> time=130.000..2629617.000 rows=254576 loops=1)
> 9 -> Index Scan using uesapt001 on APORTES (cost=0.00..37301678.64
> rows=9339331 width=25) (actual time=110.000..2520690.000 rows=9335892 loops=1)

Given the relatively small estimated number of group rows, I'd have
expected the thing to use a seqscan and HashAggregate for this part.
Do you have enable_hashagg turned off for some reason? Or enable_seqscan?

regards, tom lane

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