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From: Korisk <Korisk@yandex.ru>
To: Ondrej Ivanič <ondrej.ivanic@gmail.com>
Cc: Sergey Konoplev <gray.ru@gmail.com>
Cc: Craig Ringer <ringerc@ringerc.id.au>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: hash aggregation
Date: Fri, 12 Oct 2012 18:37:48 +0400
Message-ID: <846851350052668@web19g.yandex.ru> (raw)
In-Reply-To: <CAM6mieJT5tyMz0kgESUEgNSvNBhdcoBCPSX5X_WFW6Rs2HugQg@mail.gmail.com>
References: <118871349885342@web16f.yandex.ru>
	<CAL_0b1tHHHGz=umGWm=FXkSkt+yCJh-Cb10BJLoD-i3mwvNeaQ@mail.gmail.com>
	<323831349928808@web5g.yandex.ru>
	<50764D55.2060401@ringerc.id.au>
	<53981349968513@web6f.yandex.ru>
	<CAL_0b1tap1pSQ78t482ynYN_2yBqpYQnmJAXNC3zS023+=Xqqg@mail.gmail.com>
	<246351350014151@web25e.yandex.ru>
	<CAL_0b1v1yGzkLsnCS=8Cxh8awPa22F5OZYM4NcpvpYijFcABLA@mail.gmail.com>
	<270381350015278@web27h.yandex.ru>
	<CAM6mieJT5tyMz0kgESUEgNSvNBhdcoBCPSX5X_WFW6Rs2HugQg@mail.gmail.com>

> What I can not understand is why the seq scan's estimated cost is
> better the index scan's one. It depends on the number of pages in
> index/relation. May be the index is heavily bloated?
Mm i don't know how to see bloating level. But the index was created by 
create index on hashcheck using btree (name)
after the table population.

Sizes:
hashes=# select pg_total_relation_size('hashcheck');
 pg_total_relation_size 
------------------------
             2067701760
(1 row)

hashes=# select pg_total_relation_size('hashcheck_name_rev_idx');
 pg_total_relation_size 
------------------------
              629170176
(1 row)

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