From: "Yuzuko Hosoya" <hosoya.yuzuko@lab.ntt.co.jp>
References: <00e601d4ca86$932b8bc0$b982a340$@lab.ntt.co.jp>
 <afef4fb8-c448-d54a-9628-7c26277d4895@lab.ntt.co.jp>
In-Reply-To: <afef4fb8-c448-d54a-9628-7c26277d4895@lab.ntt.co.jp>
Subject: RE: Problem with default partition pruning
Date: Wed, 27 Feb 2019 15:50:39 +0900
Message-ID: <010e01d4ce68$c0427b10$40c77130$@lab.ntt.co.jp>
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Content-language: ja
Thread-Index: AQLwSThp7L0tC61luGAd4dJt3HxY3QJvrgn9o6jA3LA=
To: "'Amit Langote'" <Langote_Amit_f8@lab.ntt.co.jp>,
        "'PostgreSQL Hackers'" <pgsql-hackers@lists.postgresql.org>
Precedence: bulk

Amit-san,

> From: Amit Langote [mailto:Langote_Amit_f8@lab.ntt.co.jp]
> Sent: Wednesday, February 27, 2019 11:22 AM
> 
> Hosoya-san,
> 
> On 2019/02/22 17:14, Yuzuko Hosoya wrote:
> > Hi,
> >
> > I found the bug of default partition pruning when executing a range query.
> >
> > -----
> > postgres=# create table test1(id int, val text) partition by range
> > (id); postgres=# create table test1_1 partition of test1 for values
> > from (0) to (100); postgres=# create table test1_2 partition of test1
> > for values from (150) to (200); postgres=# create table test1_def
> > partition of test1 default;
> >
> > postgres=# explain select * from test1 where id > 0 and id < 30;
> >                            QUERY PLAN
> > ----------------------------------------------------------------
> >  Append  (cost=0.00..11.83 rows=59 width=11)
> >    ->  Seq Scan on test1_1  (cost=0.00..5.00 rows=58 width=11)
> >          Filter: ((id > 0) AND (id < 30))
> >    ->  Seq Scan on test1_def  (cost=0.00..6.53 rows=1 width=12)
> >          Filter: ((id > 0) AND (id < 30))
> > (5 rows)
> >
> > There is no need to scan the default partition, but it's scanned.
> > -----
> >
> > In the current implement, whether the default partition is scanned or
> > not is determined according to each condition of given WHERE clause at
> > get_matching_range_bounds().  In this example, scan_default is set
> > true according to id > 0 because id >= 200 matches the default
> > partition.  Similarly, according to id < 30, scan_default is set true.
> > Then, these results are combined according to AND/OR at perform_pruning_combine_step().
> > In this case, final result's scan_default is set true.
> >
> > The modifications I made are as follows:
> > - get_matching_range_bounds() determines only offsets of range bounds
> >   according to each condition
> > - These results are combined at perform_pruning_combine_step()
> > - Whether the default partition is scanned or not is determined at
> >   get_matching_partitions()
> >
> > Attached the patch.  Any feedback is greatly appreciated.
> 
> Thank you for reporting.  Can you please add this to March CF in Bugs category so as not to lose
track
> of this?
> 
> I will try to send review comments soon.
> 
Thank you for your reply.  I added this to March CF.

Regards,
Yuzuko Hosoya
NTT Open Source Software Center