Обсуждение: Explain query on table with partition tables

I've made a master table named master and twelve partitions tables. I've
made all constraint on column "timpul" in partition tables and all
neccesary rules on insert operation. I've comment out constraint_exclusion
and put true for that variable into postgresql.conf. I've restarted server.

I run EXPLAIN PLAN for SELECT * FROM MASTER WHERE timpul = '2006-01-01'
and doesn't look that scan only one corect partition table (as I read from
docs). It looks like:
                                              QUERY PLAN
-----------------------------------------------------------------------------------------------------
  Result  (cost=0.00..100.50 rows=43 width=80)
    ->  Append  (cost=0.00..100.50 rows=43 width=80)
          ->  Seq Scan on master  (cost=0.00..18.88 rows=4 width=80)
                Filter: (timpul = '2006-01-01 00:00:00'::timestamp without
time zone)
          ->  Seq Scan on master_012006 master  (cost=0.00..1.01 rows=1
width=23)
                Filter: (timpul = '2006-01-01 00:00:00'::timestamp without
time zone)
          ->  Bitmap Heap Scan on master_022006 master  (cost=2.01..9.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_022006__timpul
(cost=0.00..2.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Bitmap Heap Scan on master_032006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_032006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Seq Scan on master_042006 master  (cost=0.00..1.00 rows=1
width=80)
                Filter: (timpul = '2006-01-01 00:00:00'::timestamp without
time zone)
          ->  Bitmap Heap Scan on master_052006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_052006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Bitmap Heap Scan on master_062006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_062006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Bitmap Heap Scan on master_072006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_072006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Bitmap Heap Scan on master_082006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_082006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Bitmap Heap Scan on master_092006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_092006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Bitmap Heap Scan on master_102006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_102006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Bitmap Heap Scan on master_112006 master  (cost=1.01..8.62
rows=4 width=80)
                Recheck Cond: (timpul = '2006-01-01 00:00:00'::timestamp
without time zone)
                ->  Bitmap Index Scan on idx1_master_112006__timpul
(cost=0.00..1.01 rows=4 width=0)
                      Index Cond: (timpul = '2006-01-01
00:00:00'::timestamp without time zone)
          ->  Seq Scan on master_122006 master  (cost=0.00..1.01 rows=1
width=23)
                Filter: (timpul = '2006-01-01 00:00:00'::timestamp without
time zone)
(46 rows)
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"Pazargic Antonel Ernest" <antonel.pazargic@gmail.com> writes:
> I've made a master table named master and twelve partitions tables. I've
> made all constraint on column "timpul" in partition tables and all
> neccesary rules on insert operation. I've comment out constraint_exclusion
> and put true for that variable into postgresql.conf. I've restarted server.

> I run EXPLAIN PLAN for SELECT * FROM MASTER WHERE timpul = '2006-01-01'
> and doesn't look that scan only one corect partition table (as I read from
> docs). It looks like:

It works for me (tiny example attached).  You might want to try "show
constraint_exclusion" just to verify you turned it on correctly.

            regards, tom lane

regression=# create table master (timpul timestamp);
CREATE TABLE
regression=# create table t1 (check (timpul >= '2005-01-01' and timpul < '2006-01-01')) inherits (master);
CREATE TABLE
regression=# create table t2 (check (timpul >= '2006-01-01' and timpul < '2007-01-01')) inherits (master);
CREATE TABLE
regression=# explain select * from master where timpul = '2005-10-01';
                                     QUERY PLAN
-------------------------------------------------------------------------------------
 Result  (cost=0.00..102.75 rows=30 width=8)
   ->  Append  (cost=0.00..102.75 rows=30 width=8)
         ->  Seq Scan on master  (cost=0.00..34.25 rows=10 width=8)
               Filter: (timpul = '2005-10-01 00:00:00'::timestamp without time zone)
         ->  Seq Scan on t1 master  (cost=0.00..34.25 rows=10 width=8)
               Filter: (timpul = '2005-10-01 00:00:00'::timestamp without time zone)
         ->  Seq Scan on t2 master  (cost=0.00..34.25 rows=10 width=8)
               Filter: (timpul = '2005-10-01 00:00:00'::timestamp without time zone)
(8 rows)

regression=# set constraint_exclusion to 1;
SET
regression=# explain select * from master where timpul = '2005-10-01';
                                     QUERY PLAN
-------------------------------------------------------------------------------------
 Result  (cost=0.00..68.50 rows=20 width=8)
   ->  Append  (cost=0.00..68.50 rows=20 width=8)
         ->  Seq Scan on master  (cost=0.00..34.25 rows=10 width=8)
               Filter: (timpul = '2005-10-01 00:00:00'::timestamp without time zone)
         ->  Seq Scan on t1 master  (cost=0.00..34.25 rows=10 width=8)
               Filter: (timpul = '2005-10-01 00:00:00'::timestamp without time zone)
(6 rows)

regression=#