From: | "Yuzuko Hosoya" <hosoya(dot)yuzuko(at)lab(dot)ntt(dot)co(dot)jp> |
---|---|
To: | "'PostgreSQL Hackers'" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Cc: | "'Amit Langote'" <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
Subject: | Problem with default partition pruning |
Date: | 2019-02-22 08:14:04 |
Message-ID: | 00e601d4ca86$932b8bc0$b982a340$@lab.ntt.co.jp |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
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.
Best regards,
---
Yuzuko Hosoya
NTT Open Source Software Center
Attachment | Content-Type | Size |
---|---|---|
default_partition_pruning.patch | application/octet-stream | 12.5 KB |
From | Date | Subject | |
---|---|---|---|
Next Message | Etsuro Fujita | 2019-02-22 08:17:24 | Re: Problems with plan estimates in postgres_fdw |
Previous Message | Haribabu Kommi | 2019-02-22 08:10:49 | Re: pg_basebackup ignores the existing data directory permissions |