From: martial.bizel@free.fr
To: pgsql-performance@postgresql.org
Subject: Re: explain hashAggregate
Date: Wed, 15 Feb 2006 16:56:07 +0100
Message-ID: <1140018967.43f34f1761803@imp2-g19.free.fr> (raw)
In-Reply-To: <1140018387.43f34cd36a076@imp2-g19.free.fr>
References: <20060215090446.2F3AC1B819F@mx1.hub.org>
<1140018387.43f34cd36a076@imp2-g19.free.fr>
Good morning,
I try to understand how optimizer uses HashAggregate instead of GroupAggregate
and I want to know what is exactly this two functionnality (benefits
/inconvenients)
In my case, I've this explain plan.
-----------------------
Nested Loop (cost=2451676.23..2454714.73 rows=1001 width=34)
-> Subquery Scan "day" (cost=2451676.23..2451688.73 rows=1000 width=16)
-> Limit (cost=2451676.23..2451678.73 rows=1000 width=12)
-> Sort (cost=2451676.23..2451684.63 rows=3357 width=12)
Sort Key: sum(occurence)
-> HashAggregate (cost=2451471.24..2451479.63 rows=3357
width=12)
-> Index Scan using test_date on
queries_detail_statistics (cost=0.00..2449570.55 rows=380138 width=12)
Index Cond: ((date >= '2006-01-01'::date) AND
(date <= '2006-01-30'::date))
Filter: (((portal)::text = '1'::text) OR
((portal)::text = '2'::text))
-> Index Scan using query_string_pkey on query_string (cost=0.00..3.01
rows=1 width=34)
Index Cond: ("outer".query = query_string.id)
----------------------------
How to get necessary memory RAM for this explain plan ?
thanks a lot
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To: pgsql-performance@postgresql.org
Cc: martial.bizel@free.fr
Subject: Re: explain hashAggregate
In-Reply-To: <1140018967.43f34f1761803@imp2-g19.free.fr>
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