To: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
From: Clailson <clailson.dba@gmail.com>
Subject: Optimization inner join
Message-ID: <7ad1128e-7fdb-9976-823c-d4abdf554fa2@gmail.com>
Date: Thu, 19 Jan 2017 07:08:47 -0300
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Hi,

Is there something in the roadmap to optimize the inner join?

I've this situation above. Table b has 400 rows with null in the column b.

explain analyze select * from a inner join b on (b.b = a.a);

"Merge Join  (cost=0.55..65.30 rows=599 width=16) (actual time=0.030..1.173 rows=599 loops=1)"
"  Merge Cond: (a.a = b.b)"
"  ->  Index Scan using a_pkey on a  (cost=0.28..35.27 rows=1000 width=8) (actual time=0.014..0.364 rows=1000 loops=1)"
"  ->  Index Scan using in01 on b  (cost=0.28..33.27 rows=1000 width=8) (actual time=0.012..0.249 rows=600 loops=1)"
"Total runtime: 1.248 ms"

My question is: Why the planner isn't removing the null rows during the 
scan of table b?

-- 
Clailson Soares Dinízio de Almeida


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    <font size="-1"><font face="Arial">Hi,<br>
        <br>
        Is there something in the roadmap to optimize the inner join?<br>
        <br>
        I've this situation </font></font>above. Table b ha<font
      size="-1"><font face="Arial">s 400 rows with null in the column b.<br>
      </font></font><br>
    explain analyze select * from a inner join b on (b.b = a.a);
    <pre>"Merge Join  (cost=0.55..65.30 rows=599 width=16) (actual time=0.030..1.173 rows=599 loops=1)" 
"  Merge Cond: (a.a = b.b)" 
"  -&gt;  Index Scan using a_pkey on a  (cost=0.28..35.27 rows=1000 width=8) (actual time=0.014..0.364 rows=1000 loops=1)" 
"  -&gt;  Index Scan using in01 on b  (cost=0.28..33.27 rows=1000 width=8) (actual time=0.012..0.249 rows=600 loops=1)" 
"Total runtime: 1.248 ms" 

<font size="-1"><font face="Arial">My question is: Why the planner isn't removing the null rows during the scan of table b?</font></font>
</pre>
    <pre class="moz-signature" cols="72">-- 
Clailson Soares Dinízio de Almeida
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