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	id 1IR7kf-0001Y4-Jm; Fri, 31 Aug 2007 15:45:37 +0100
To: "Aleksandr Vinokurov" <aleksandr.vin@gmail.com>
Cc: <pgsql-sql@postgresql.org>
Subject: Re: Incomprehensible dogged sort in Merge Join
In-Reply-To: <46D82318.3070700@gmail.com> (Aleksandr Vinokurov's message of
	"Fri\, 31 Aug 2007 18\:18\:00 +0400")
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From: Gregory Stark <stark@enterprisedb.com>
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Date: Fri, 31 Aug 2007 15:45:37 +0100
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"Aleksandr Vinokurov" <aleksandr.vin@gmail.com> writes:

> And that is its plan (attached one is the same, but with costs):
>
>>---------------------------------<cut>--------------------------------<
>  Merge Left Join
>    Merge Cond: ("outer".name =3D "inner".name)
>    ->  Sort
>          Sort Key: log.name
>          ->  Seq Scan on log_example_3 log
>    ->  Sort
>          Sort Key: uh.name
>          ->  Subquery Scan uh
>                ->  Sort
>                      Sort Key: name
>                      ->  Seq Scan on user_history
>>---------------------------------<cut>--------------------------------<

What version are you running with?

Incidentally with CVS HEAD I see it working:

postgres=3D# explain select * from (select * from a order by i) as a right =
join b on a.i =3D b.i ;
                           QUERY PLAN=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
-----------------------------------------------------------------
 Merge Right Join  (cost=3D299.56..675.13 rows=3D22898 width=3D16)
   Merge Cond: (public.a.i =3D b.i)
   ->  Sort  (cost=3D149.78..155.13 rows=3D2140 width=3D8)
         Sort Key: public.a.i
         ->  Seq Scan on a  (cost=3D0.00..31.40 rows=3D2140 width=3D8)
   ->  Sort  (cost=3D149.78..155.13 rows=3D2140 width=3D8)
         Sort Key: b.i
         ->  Seq Scan on b  (cost=3D0.00..31.40 rows=3D2140 width=3D8)
(8 rows)



> With best regards to all of you,
> Aleksandr.