From: Yuzuko Hosoya <hosoya.yuzuko@lab.ntt.co.jp>
To: pgsql-hackers@lists.postgresql.org
Subject: Runtime pruning problem
Date: Tue, 16 Apr 2019 20:54:36 +0900
Message-ID: <001001d4f44b$2a2cca50$7e865ef0$@lab.ntt.co.jp> (raw)
Hi all,
I found a runtime pruning test case which may be a problem as follows:
----
create table t1 (id int, dt date) partition by range(dt);
create table t1_1 partition of t1 for values from ('2019-01-01') to ('2019-04-01');
create table t1_2 partition of t1 for values from ('2019-04-01') to ('2019-07-01');
create table t1_3 partition of t1 for values from ('2019-07-01') to ('2019-10-01');
create table t1_4 partition of t1 for values from ('2019-10-01') to ('2020-01-01');
In this example, current_date is 2019-04-16.
postgres=# explain select * from t1 where dt = current_date + 400;
QUERY PLAN
------------------------------------------------------------
Append (cost=0.00..198.42 rows=44 width=8)
Subplans Removed: 3
-> Seq Scan on t1_1 (cost=0.00..49.55 rows=11 width=8)
Filter: (dt = (CURRENT_DATE + 400))
(4 rows)
postgres=# explain analyze select * from t1 where dt = current_date + 400;
QUERY PLAN
---------------------------------------------------------------------------------------
Append (cost=0.00..198.42 rows=44 width=8) (actual time=0.000..0.001 rows=0 loops=1)
Subplans Removed: 3
-> Seq Scan on t1_1 (cost=0.00..49.55 rows=11 width=8) (never executed)
Filter: (dt = (CURRENT_DATE + 400))
Planning Time: 0.400 ms
Execution Time: 0.070 ms
(6 rows)
----
I realized t1_1 was not scanned actually since "never executed"
was displayed in the plan using EXPLAIN ANALYZE. But I think
"One-Time Filter: false" and "Subplans Removed: ALL" or something
like that should be displayed instead.
What do you think?
Best regards,
Yuzuko Hosoya
NTT Open Source Software Center
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To: pgsql-hackers@postgresql.org
Cc: hosoya.yuzuko@lab.ntt.co.jp, pgsql-hackers@lists.postgresql.org
Subject: Re: Runtime pruning problem
In-Reply-To: <001001d4f44b$2a2cca50$7e865ef0$@lab.ntt.co.jp>
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