Le 28/02/2019 à 09:26, Imai, Yoshikazu a écrit : > Hosoya-san > > On Wed, Feb 27, 2019 at 6:51 AM, Yuzuko Hosoya wrote: >>> From: Amit Langote [mailto:langote_amit...@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. > I tested with simple use case and I confirmed it works correctly like below. > > In case using between clause: > 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; > > [HEAD] > postgres=# explain analyze select * from test1 where id between 0 and 50; > QUERY PLAN > > ----------------------------------------------------------------------------------------------------------- > Append (cost=0.00..58.16 rows=12 width=36) (actual time=0.008..0.008 rows=0 > loops=1) > -> Seq Scan on test1_1 (cost=0.00..29.05 rows=6 width=36) (actual > time=0.005..0.005 rows=0 loops=1) > Filter: ((id >= 0) AND (id <= 50)) > -> Seq Scan on test1_def (cost=0.00..29.05 rows=6 width=36) (actual > time=0.002..0.002 rows=0 loops=1) > Filter: ((id >= 0) AND (id <= 50)) > > > [patched] > postgres=# explain analyze select * from test1 where id between 0 and 50; > QUERY PLAN > > --------------------------------------------------------------------------------------------------------- > Append (cost=0.00..29.08 rows=6 width=36) (actual time=0.006..0.006 rows=0 > loops=1) > -> Seq Scan on test1_1 (cost=0.00..29.05 rows=6 width=36) (actual > time=0.004..0.005 rows=0 loops=1) > Filter: ((id >= 0) AND (id <= 50)) > > > > I considered about another use case. If default partition contains rows whose > id = 300 and then we add another partition which have constraints like id >= > 300 and id < 400, I thought we won't scan the rows anymore. But I noticed we > simply can't add such a partition. > > postgres=# insert into test1 values (300); > INSERT 0 1 > postgres=# create table test1_3 partition of test1 for values from (300) to > (400); > ERROR: updated partition constraint for default partition "test1_def" would > be violated by some row > > > So I haven't come up with bad cases so far :) > > -- > Yoshikazu Imai
Hello Yoshikazu-San, I tested your patch using some sub-partitions and found a possible problem. I create a new partitioned partition test1_3 with 2 sub-partitions : ------------------------- create table test1_3 partition of test1 for values from (200) to (400) partition by range (id); create table test1_3_1 partition of test1_3 for values from (200) to (250); create table test1_3_2 partition of test1_3 for values from (250) to (350); # explain select * from test1 where (id > 0 and id < 30); QUERY PLAN --------------------------------------------------------------- Append (cost=0.00..29.08 rows=6 width=36) -> Seq Scan on test1_1 (cost=0.00..29.05 rows=6 width=36) Filter: ((id > 0) AND (id < 30)) (3 rows) # explain select * from test1 where (id > 220 and id < 230); QUERY PLAN ----------------------------------------------------------------- Append (cost=0.00..29.08 rows=6 width=36) -> Seq Scan on test1_3_1 (cost=0.00..29.05 rows=6 width=36) Filter: ((id > 220) AND (id < 230)) (3 rows) # explain select * from test1 where (id > 0 and id < 30) or (id > 220 and id < 230); QUERY PLAN --------------------------------------------------------------------------- Append (cost=0.00..106.40 rows=39 width=36) -> Seq Scan on test1_1 (cost=0.00..35.40 rows=13 width=36) Filter: (((id > 0) AND (id < 30)) OR ((id > 220) AND (id < 230))) -> Seq Scan on test1_3_1 (cost=0.00..35.40 rows=13 width=36) Filter: (((id > 0) AND (id < 30)) OR ((id > 220) AND (id < 230))) -> Seq Scan on test1_3_2 (cost=0.00..35.40 rows=13 width=36) Filter: (((id > 0) AND (id < 30)) OR ((id > 220) AND (id < 230))) (7 rows) ----------------- Partition pruning is functioning when only the sub-partition is required. When both the partition and the sub-partition is required, there is no pruning on the sub-partition. Cordialement, -- Thibaut Madelaine Dalibo
