Re: Partitioning and constraint exclusion - Mailing list pgsql-general
| From | Jayadevan M |
|---|---|
| Subject | Re: Partitioning and constraint exclusion |
| Date | |
| Msg-id | CAFS1N4jXADP7P-U6-hZMMKtq0oizYLxwxXJipQkZVEshg1fcmA@mail.gmail.com Whole thread Raw |
| In response to | Re: Partitioning and constraint exclusion ("David G. Johnston" <david.g.johnston@gmail.com>) |
| List | pgsql-general |
I am not sure but am doubting it is intelligent enough to recognize the functional expression even if all of the values are present. "simple equality" (http://www.postgresql.org/docs/9.4/interactive/ddl-partitioning.html) this is not.
Looks like the tables with about 100+ values in the check list gets pulled in, even with constraint exclusion on. I created a simple test case. One parent table with just one column, and 3 child tables with one column.
test=# \d+ parent
Table "public.parent"
Column | Type | Modifiers | Storage | Stats target | Description
--------+---------+-----------+---------+--------------+-------------
id | integer | | plain | |
Child tables: child1,
child2,
child3
test=# \d+ child1
Table "public.child1"
Column | Type | Modifiers | Storage | Stats target | Description
--------+---------+-----------+---------+--------------+-------------
id | integer | | plain | |
Check constraints:
"c" CHECK (id = ANY (ARRAY[1, 2]))
Inherits: parent
test=# \d+ child2
Table "public.child2"
Column | Type | Modifiers | Storage | Stats target | Description
--------+---------+-----------+---------+--------------+-------------
id | integer | | plain | |
Check constraints:
"c" CHECK (id = ANY (ARRAY[3, 4]))
Inherits: parent
test=# \d+ child3
Table "public.child3"
Column | Type | Modifiers | Storage | Stats target | Description
--------+---------+-----------+---------+--------------+-------------
id | integer | | plain | |
Check constraints:
"c3" CHECK (id = ANY (ARRAY[5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100]))
Inherits: parent
test=# explain analyze select * from parent where id = 1;
QUERY PLAN
--------------------------------------------------------------------------------------------------------
Append (cost=0.00..40.00 rows=13 width=4) (actual time=0.002..0.002 rows=0 loops=1)
-> Seq Scan on parent (cost=0.00..0.00 rows=1 width=4) (actual time=0.001..0.001 rows=0 loops=1)
Filter: (id = 1)
-> Seq Scan on child1 (cost=0.00..40.00 rows=12 width=4) (actual time=0.000..0.000 rows=0 loops=1)
Filter: (id = 1)
Total runtime: 0.029 ms
If I increase the number of values a bit more.....
with t as (select generate_series(5,110) x ) select 'alter table child3 add constraint c3 check ( id in ( ' || string_agg(x::text,',') || ' )) ; ' from t;
test=# explain analyze select * from parent where id = 1;
QUERY PLAN
--------------------------------------------------------------------------------------------------------
Append (cost=0.00..80.00 rows=25 width=4) (actual time=0.003..0.003 rows=0 loops=1)
-> Seq Scan on parent (cost=0.00..0.00 rows=1 width=4) (actual time=0.001..0.001 rows=0 loops=1)
Filter: (id = 1)
-> Seq Scan on child1 (cost=0.00..40.00 rows=12 width=4) (actual time=0.000..0.000 rows=0 loops=1)
Filter: (id = 1)
-> Seq Scan on child3 (cost=0.00..40.00 rows=12 width=4) (actual time=0.000..0.000 rows=0 loops=1)
Filter: (id = 1)
Thanks,
Jayadevan
David J.
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