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Message-ID: <46D82C11.5090506@gmail.com>
Date: Fri, 31 Aug 2007 18:56:17 +0400
From: Aleksandr Vinokurov <aleksandr.vin@gmail.com>
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To: Gregory Stark <stark@enterprisedb.com>
CC: pgsql-sql@postgresql.org
Subject: Re: Incomprehensible dogged sort in Merge Join
References: <46D82318.3070700@gmail.com> <877inb225q.fsf@oxford.xeocode.com>
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Gregory Stark wrote:
> "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 = "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?

8.0.1, sorry for missing.

> 
> Incidentally with CVS HEAD I see it working:
> 
> postgres=# explain select * from (select * from a order by i) as a right join b on a.i = b.i ;
>                            QUERY PLAN                            
> -----------------------------------------------------------------
>  Merge Right Join  (cost=299.56..675.13 rows=22898 width=16)
>    Merge Cond: (public.a.i = b.i)
>    ->  Sort  (cost=149.78..155.13 rows=2140 width=8)
>          Sort Key: public.a.i
>          ->  Seq Scan on a  (cost=0.00..31.40 rows=2140 width=8)
>    ->  Sort  (cost=149.78..155.13 rows=2140 width=8)
>          Sort Key: b.i
>          ->  Seq Scan on b  (cost=0.00..31.40 rows=2140 width=8)
> (8 rows)
> 
> 
> 
>> With best regards to all of you,
>> Aleksandr.
>> ÿþ 
> 
> gesundheit.
> 
> 

Best wishes,
Aleksandr.