Subject: Re: WIP: Covering + unique indexes.
To: David Rowley <david.rowley@2ndquadrant.com>
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Cc: Jeff Janes <jeff.janes@gmail.com>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
From: Anastasia Lubennikova <a.lubennikova@postgrespro.ru>
Message-ID: <56965808.7050004@postgrespro.ru>
Date: Wed, 13 Jan 2016 16:58:32 +0300
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13.01.2016 04:27, David Rowley:
> I've also done some testing:
>
> create table ab (a int, b int);
> insert into ab select a,b from generate_Series(1,10) a(a), 
> generate_series(1,10000) b(b);
> set enable_bitmapscan=off;
> set enable_indexscan=off;
>
> select * from ab where a = 1 and b=1;
>  a | b
> ---+---
>  1 | 1
> (1 row)
>
> set enable_indexscan = on;
> select * from ab where a = 1 and b=1;
>  a | b
> ---+---
> (0 rows)
>
> This is broken. I've not looked into why yet, but from looking at the 
> EXPLAIN output I was a bit surprised to see b=1 as an index condition. 
> I'd have expected a Filter maybe, but I've not looked at the EXPLAIN 
> code to see how those are determined yet.

Hmm... Do you use both patches?
And could you provide index definition, I can't reproduce the problem 
assuming that index is created by the statement
CREATE INDEX idx ON ab (a) INCLUDING (b);

-- 
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company


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