Thread: partition table slow planning
We encounter a issue when we do query on partition table directly with proper partition key provide. postgres able to find problem partition but when I do explain plan it showing 95% spend on planning the execution . Here is example
itinerary=# EXPLAIN ANALYZE SELECT * FROM itinerary WHERE destination ='GRJ' AND departure_date = '2020-01-01' AND month_day = 101
itinerary-# ;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
Append (cost=0.29..13.79 rows=11 width=1024) (actual time=0.033..0.037 rows=1 loops=1)
-> Index Scan using itinerary_101_destination_departure_date_idx on itinerary_101 (cost=0.29..13.73 rows=11 width=1024) (actual time=0.033..0.036 rows=1 loops=1)
Index Cond: (((destination)::text = 'GRJ'::text) AND ((departure_date)::text = '2020-01-01'::text))
Filter: (month_day = 101)
Planning Time: 51.677 ms
Execution Time: 0.086 ms
itinerary-# ;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
Append (cost=0.29..13.79 rows=11 width=1024) (actual time=0.033..0.037 rows=1 loops=1)
-> Index Scan using itinerary_101_destination_departure_date_idx on itinerary_101 (cost=0.29..13.73 rows=11 width=1024) (actual time=0.033..0.036 rows=1 loops=1)
Index Cond: (((destination)::text = 'GRJ'::text) AND ((departure_date)::text = '2020-01-01'::text))
Filter: (month_day = 101)
Planning Time: 51.677 ms
Execution Time: 0.086 ms
When I do query on directly on the partition table it is quite fast
itinerary=# EXPLAIN ANALYZE SELECT * FROM itinerary_101 WHERE destination ='GRJ' AND departure_date = '2020-01-01' AND month_day = 101
itinerary-# ;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
Index Scan using itinerary_101_destination_departure_date_idx on itinerary_101 (cost=0.29..13.73 rows=11 width=1024) (actual time=0.043..0.048 rows=1 loops=1)
Index Cond: (((destination)::text = 'GRJ'::text) AND ((departure_date)::text = '2020-01-01'::text))
Filter: (month_day = 101)
Planning Time: 0.191 ms
Execution Time: 0.074 ms
(5 rows)
itinerary=#
itinerary-# ;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
Index Scan using itinerary_101_destination_departure_date_idx on itinerary_101 (cost=0.29..13.73 rows=11 width=1024) (actual time=0.043..0.048 rows=1 loops=1)
Index Cond: (((destination)::text = 'GRJ'::text) AND ((departure_date)::text = '2020-01-01'::text))
Filter: (month_day = 101)
Planning Time: 0.191 ms
Execution Time: 0.074 ms
(5 rows)
itinerary=#
Can we know why this is happening?
On Wed, Jul 24, 2019 at 4:24 AM Jatinder Sandhu <jatinder.sandhu@flightnetwork.com> wrote: > > > We encounter a issue when we do query on partition table directly with proper partition key provide. postgres able to findproblem partition but when I do explain plan it showing 95% spend on planning the execution . Here is example > itinerary=# EXPLAIN ANALYZE SELECT * FROM itinerary WHERE destination ='GRJ' AND departure_date = '2020-01-01' AND month_day= 101 > itinerary-# ; > QUERY PLAN > ----------------------------------------------------------------------------------------------------------------------------------------------------------------------- > Append (cost=0.29..13.79 rows=11 width=1024) (actual time=0.033..0.037 rows=1 loops=1) > -> Index Scan using itinerary_101_destination_departure_date_idx on itinerary_101 (cost=0.29..13.73 rows=11 width=1024)(actual time=0.033..0.036 rows=1 loops=1) > Index Cond: (((destination)::text = 'GRJ'::text) AND ((departure_date)::text = '2020-01-01'::text)) > Filter: (month_day = 101) > Planning Time: 51.677 ms > Execution Time: 0.086 ms > > > When I do query on directly on the partition table it is quite fast > itinerary=# EXPLAIN ANALYZE SELECT * FROM itinerary_101 WHERE destination ='GRJ' AND departure_date = '2020-01-01' ANDmonth_day = 101 > itinerary-# ; > QUERY PLAN > ----------------------------------------------------------------------------------------------------------------------------------------------------------------- > Index Scan using itinerary_101_destination_departure_date_idx on itinerary_101 (cost=0.29..13.73 rows=11 width=1024)(actual time=0.043..0.048 rows=1 loops=1) > Index Cond: (((destination)::text = 'GRJ'::text) AND ((departure_date)::text = '2020-01-01'::text)) > Filter: (month_day = 101) > Planning Time: 0.191 ms > Execution Time: 0.074 ms > (5 rows) > > itinerary=# > > Can we know why this is happening? > I guess when you give the query on the parent table, based on your clause it need to search which partition to scan that can increase the planning time. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com