Message-ID: <4FD1FF14.9060303@gmail.com>
Date: Fri, 08 Jun 2012 21:33:08 +0800
From: Rural Hunter <ruralhunter@gmail.com>
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To: pgsql-performance@postgresql.org
Subject: how to change the index chosen in plan?
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I have a query like this:
select a.* from a inner join b on a.aid=b.aid where a.col1=33 a.col2=44 
and b.bid=8
postgresql selected the index on a.col1 then selected the index on 
b.bid. But in my situation, I know that the query will be faster if it 
chose the index on b.bid first since there are only a few rows with 
value 8. So I re-wrote the query as below:
select a.* from a where a.aid in (select aid from b where bid=8) and 
a.col1=33 a.col2=44
But surprisingly, postgresql didn't change the plan. it still chose to 
index scan on a.col1. How can I re-wirte the query so postgresql will 
scan on b.bid first?