Skip site navigation (1) Skip section navigation (2)

BUG #6662: Database do not push condition to subquery,test case for bug 6658

From: maxim(dot)boguk(at)gmail(dot)com
To: pgsql-bugs(at)postgresql(dot)org
Subject: BUG #6662: Database do not push condition to subquery,test case for bug 6658
Date: 2012-05-23 01:13:04
Message-ID: E1SX08O-00085J-HA@wrigleys.postgresql.org (view raw or flat)
Thread:
Lists: pgsql-bugs
The following bug has been logged on the website:

Bug reference:      6662
Logged by:          Maxim Boguk
Email address:      maxim(dot)boguk(at)gmail(dot)com
PostgreSQL version: 9.1.3
Operating system:   Linux
Description:        

I managed create simple self-contained test case for 6658.



create table test as select * from generate_series(1,100000) as g(val);
create index test_val_special on test((val || ''));
analyze test;
select count(*) from test;

--ok
--index scan
explain analyze
SELECT val
FROM test
WHERE (val || '')='something';


                                                      QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------
 Index Scan using test_val_special on test  (cost=0.01..8.29 rows=1 width=4)
(actual time=0.011..0.011 rows=0 loops=1)
   Index Cond: (((val)::text || ''::text) = 'something'::text)
 Total runtime: 0.038 ms


--not ok
--seq scan on 9.1.3
explain analyze
SELECT val 
FROM
(
SELECT
val,
(val || '') AS search_string
FROM test
) AS t1
WHERE search_string='something';

                                                    QUERY PLAN
------------------------------------------------------------------------------------------------------------------
 Subquery Scan on t1  (cost=0.00..3443.00 rows=500 width=4) (actual
time=47.076..47.076 rows=0 loops=1)
   Filter: (t1.search_string = 'something'::text)
   ->  Seq Scan on test  (cost=0.00..2193.00 rows=100000 width=4) (actual
time=0.012..34.949 rows=100000 loops=1)
 Total runtime: 47.091 ms


--the same second query on 8.3.13
--plan correct
                                                      QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------
 Index Scan using test_val_special on test  (cost=0.01..8.29 rows=1 width=4)
(actual time=0.004..0.004 rows=0 loops=1)
   Index Cond: (((val)::text || ''::text) = 'something'::text)
 Total runtime: 0.018 ms

Kind Regards,
Maksym


Responses

pgsql-bugs by date

Next:From: Tom LaneDate: 2012-05-23 01:46:04
Subject: Re: BUG #6662: Database do not push condition to subquery, test case for bug 6658
Previous:From: Valentine GogichashviliDate: 2012-05-23 00:11:30
Subject: Re: BUG #6661: out-of-order XID insertion in KnownAssignedXids

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group