PostgreSQL分区约束行为奇怪

Question

我有一个由两个列( expired和type_id )划分的表。expired是按范围划分的布尔值和type_id分区。表例：

mos_active_1
...
mos_active_15
mos_expired_1
...
mos_expired_15

我的约束设置如下：

ADD CONSTRAINT mos_active_1_check CHECK (expired = false AND type_id < 100 )
...
ADD CONSTRAINT mos_expired_1_check CHECK (expired = true AND type_id < 100 )

如果我现在运行一个SELECT * from mos WHERE expired = true AND type_id = 34 --一切都像预期的那样工作，那么只会命中mos_expired_1。

Result  (cost=0.00..19.77 rows=2 width=627)
  ->  Append  (cost=0.00..19.77 rows=2 width=627)
        ->  Seq Scan on mos  (cost=0.00..11.50 rows=1 width=627)
              Filter: (expired AND (type_id = 34))
        ->  Index Scan using index_mos_expired_1_on_type_id_and_region_id on mos_expired_1 mos  (cost=0.00..8.27 rows=1 width=627)
              Index Cond: (type_id = 34)
              Filter: expired

奇怪的是，SELECT * from mos WHERE expired = false AND type_id = 34做而不是工作。EXPLAIN显示，mos_expired_1和mos_active_1都是被查询的。

Result  (cost=0.00..2464.71 rows=5863 width=150)
  ->  Append  (cost=0.00..2464.71 rows=5863 width=150)
        ->  Seq Scan on mos  (cost=0.00..11.50 rows=1 width=627)
              Filter: ((NOT expired) AND (type_id = 34))
        ->  Index Scan using index_mos_expired_1_on_type_id_and_region_id on mos_expired_1 mos  (cost=0.00..8.27 rows=1 width=627)
              Index Cond: (type_id = 34)
              Filter: (NOT expired)
        ->  Bitmap Heap Scan on mos_active_1 mos  (cost=113.68..2444.95 rows=5861 width=150)
              Recheck Cond: (type_id = 34)
              Filter: (NOT expired)
              ->  Bitmap Index Scan on index_mos_active_1_on_type_id  (cost=0.00..112.22 rows=5861 width=0)
                    Index Cond: (type_id = 34)

完全SQL (除了实际创建mos表之外)

我真的很想知道我是不是遗漏了什么，或者这是一个查询计划问题。

更新：I能够用一个简单得多的例子再现同样的问题，只有两个表具有一个基于过期的约束：

CREATE TABLE mos (type_id   INTEGER UNIQUE, expired boolean);
CREATE TABLE mos_expired_1 ( CHECK ( expired = true  ) ) INHERITS (mos);
CREATE TABLE mos_active_1 ( CHECK ( expired = false ) ) INHERITS (mos);
INSERT INTO mos_expired_1 (type_id,expired) VALUES(1, true);
INSERT INTO mos_active_1 (type_id,expired) VALUES(2, false);
EXPLAIN SELECT * from mos where expired = false;
EXPLAIN SELECT * from mos where expired = true;

Answer 1

在PostgreSQL中，对布尔人的约束排除不起作用。当您使用integer或enum时，它工作得很好。

整数：

CREATE TABLE mos (type_id INTEGER UNIQUE, expired int);
CREATE TABLE mos_expired_1 ( CHECK ( expired = 0 ) ) INHERITS (mos);
CREATE TABLE mos_active_1 ( CHECK ( expired = 1 ) ) INHERITS (mos); 
INSERT INTO mos_expired_1 (type_id,expired) VALUES(1, 0);
INSERT INTO mos_active_1 (type_id,expired) VALUES(2, 1); 
analyze;

EXPLAIN SELECT * from mos where expired = 0;
                                 QUERY PLAN                                  
-----------------------------------------------------------------------------
 Result  (cost=0.00..37.76 rows=12 width=8)
   ->  Append  (cost=0.00..37.76 rows=12 width=8)
         ->  Seq Scan on mos  (cost=0.00..36.75 rows=11 width=8)
               Filter: (expired = 0)
         ->  Seq Scan on mos_expired_1 mos  (cost=0.00..1.01 rows=1 width=8)
               Filter: (expired = 0)
(6 rows)

EXPLAIN SELECT * from mos where expired = 1;
                                 QUERY PLAN                                 
----------------------------------------------------------------------------
 Result  (cost=0.00..37.76 rows=12 width=8)
   ->  Append  (cost=0.00..37.76 rows=12 width=8)
         ->  Seq Scan on mos  (cost=0.00..36.75 rows=11 width=8)
               Filter: (expired = 1)
         ->  Seq Scan on mos_active_1 mos  (cost=0.00..1.01 rows=1 width=8)
               Filter: (expired = 1)
(6 rows)

Enum：

CREATE TYPE mybool AS ENUM ('true', 'false');                                     
CREATE TABLE mos (type_id INTEGER UNIQUE, expired mybool);
CREATE TABLE mos_expired_1 ( CHECK ( expired = 'true' ) ) INHERITS (mos);
CREATE TABLE mos_active_1 ( CHECK ( expired = 'false' ) ) INHERITS (mos);
INSERT INTO mos_expired_1 (type_id,expired) VALUES(1, 'true');
INSERT INTO mos_active_1 (type_id,expired) VALUES(2, 'false');
analyze;

EXPLAIN SELECT * from mos where expired = 'true';
                                 QUERY PLAN                                  
-----------------------------------------------------------------------------
 Result  (cost=0.00..37.76 rows=12 width=8)
   ->  Append  (cost=0.00..37.76 rows=12 width=8)
         ->  Seq Scan on mos  (cost=0.00..36.75 rows=11 width=8)
               Filter: (expired = 'true'::mybool)
         ->  Seq Scan on mos_expired_1 mos  (cost=0.00..1.01 rows=1 width=8)
               Filter: (expired = 'true'::mybool)
(6 rows)

EXPLAIN SELECT * from mos where expired = 'false';
                                 QUERY PLAN                                 
----------------------------------------------------------------------------
 Result  (cost=0.00..37.76 rows=12 width=8)
   ->  Append  (cost=0.00..37.76 rows=12 width=8)
         ->  Seq Scan on mos  (cost=0.00..36.75 rows=11 width=8)
               Filter: (expired = 'false'::mybool)
         ->  Seq Scan on mos_active_1 mos  (cost=0.00..1.01 rows=1 width=8)
               Filter: (expired = 'false'::mybool)
(6 rows)

我不知道是不是虫子。我想它在任何地方都没有记录。