Postgresql IN operator Performance: List vs Subquery -
for list of ~700 ids query performance on 20x slower passing subquery returns 700 ids. should opposite.
e.g. (first query takes under 400ms, later 9600 ms)
select date_trunc('month', day) month, sum(total) table_x y_id in (select id table_y prop = 'xyz') , day between '2015-11-05' , '2016-11-04' group month
is 20x faster on machine passing array directly:
select date_trunc('month', day) month, sum(total) table_x y_id in (1625, 1871, ..., 1640, 1643, 13291, 1458, 13304, 1407, 1765) , day between '2015-11-05' , '2016-11-04' group month
any idea problem or how optimize , obtain same performance?
the difference simple filter vs hash join:
explain analyze select t in (500,501,502,503,504,505,506,507,508,509,510,511,512,513,514,515,516,517,518,519,520,521,522,523,524,525,526,527,528,529,530,531,532,533,534,535,536,537,538,539,540,541,542,543,544,545,546,547,548,549,550,551,552,553,554,555,556,557,558,559,560,561,562,563,564,565,566,567,568,569,570,571,572,573,574,575,576,577,578,579,580,581,582,583,584,585,586,587,588,589,590,591,592,593,594,595,596,597,598,599,600); query plan ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- seq scan on t (cost=0.00..140675.00 rows=101 width=4) (actual time=0.648..1074.567 rows=101 loops=1) filter: (i = ('{500,501,502,503,504,505,506,507,508,509,510,511,512,513,514,515,516,517,518,519,520,521,522,523,524,525,526,527,528,529,530,531,532,533,534,535,536,537,538,539,540,541,542,543,544,545,546,547,548,549,550,551,552,553,554,555,556,557,558,559,560,561,562,563,564,565,566,567,568,569,570,571,572,573,574,575,576,577,578,579,580,581,582,583,584,585,586,587,588,589,590,591,592,593,594,595,596,597,598,599,600}'::integer[])) rows removed filter: 999899 planning time: 0.170 ms execution time: 1074.624 ms explain analyze select t in (select r); query plan ------------------------------------------------------------------------------------------------------------------- hash semi join (cost=3.27..17054.40 rows=101 width=4) (actual time=0.382..240.389 rows=101 loops=1) hash cond: (t.i = r.i) -> seq scan on t (cost=0.00..14425.00 rows=1000000 width=4) (actual time=0.030..117.193 rows=1000000 loops=1) -> hash (cost=2.01..2.01 rows=101 width=4) (actual time=0.074..0.074 rows=101 loops=1) buckets: 1024 batches: 1 memory usage: 12kb -> seq scan on r (cost=0.00..2.01 rows=101 width=4) (actual time=0.010..0.035 rows=101 loops=1) planning time: 0.245 ms execution time: 240.448 ms
to have same performance join array:
explain analyze select t inner join unnest( array[500,501,502,503,504,505,506,507,508,509,510,511,512,513,514,515,516,517,518,519,520,521,522,523,524,525,526,527,528,529,530,531,532,533,534,535,536,537,538,539,540,541,542,543,544,545,546,547,548,549,550,551,552,553,554,555,556,557,558,559,560,561,562,563,564,565,566,567,568,569,570,571,572,573,574,575,576,577,578,579,580,581,582,583,584,585,586,587,588,589,590,591,592,593,594,595,596,597,598,599,600]::int[] ) u (i) using (i) ; query plan ----------------------------------------------------------------------------------------------------------------------- hash join (cost=2.25..18178.25 rows=100 width=4) (actual time=0.267..243.768 rows=101 loops=1) hash cond: (t.i = u.i) -> seq scan on t (cost=0.00..14425.00 rows=1000000 width=4) (actual time=0.022..118.709 rows=1000000 loops=1) -> hash (cost=1.00..1.00 rows=100 width=4) (actual time=0.063..0.063 rows=101 loops=1) buckets: 1024 batches: 1 memory usage: 12kb -> function scan on unnest u (cost=0.00..1.00 rows=100 width=4) (actual time=0.028..0.041 rows=101 loops=1) planning time: 0.172 ms execution time: 243.816 ms
or use values
syntax:
explain analyze select t = (values (500),(501),(502),(503),(504),(505),(506),(507),(508),(509),(510),(511),(512),(513),(514),(515),(516),(517),(518),(519),(520),(521),(522),(523),(524),(525),(526),(527),(528),(529),(530),(531),(532),(533),(534),(535),(536),(537),(538),(539),(540),(541),(542),(543),(544),(545),(546),(547),(548),(549),(550),(551),(552),(553),(554),(555),(556),(557),(558),(559),(560),(561),(562),(563),(564),(565),(566),(567),(568),(569),(570),(571),(572),(573),(574),(575),(576),(577),(578),(579),(580),(581),(582),(583),(584),(585),(586),(587),(588),(589),(590),(591),(592),(593),(594),(595),(596),(597),(598),(599),(600)) ; query plan ----------------------------------------------------------------------------------------------------------------------- hash semi join (cost=2.53..17053.65 rows=101 width=4) (actual time=0.279..239.888 rows=101 loops=1) hash cond: (t.i = "*values*".column1) -> seq scan on t (cost=0.00..14425.00 rows=1000000 width=4) (actual time=0.022..117.199 rows=1000000 loops=1) -> hash (cost=1.26..1.26 rows=101 width=4) (actual time=0.059..0.059 rows=101 loops=1) buckets: 1024 batches: 1 memory usage: 12kb -> values scan on "*values*" (cost=0.00..1.26 rows=101 width=4) (actual time=0.002..0.027 rows=101 loops=1) planning time: 0.242 ms execution time: 239.933 ms
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