优化postgresql请求

Question

如何在 postgresql 中优化请求？我应该创建哪些最佳索引？

我尝试为 t_my.id、t_my.param1、t_my.param2、t_my_other.param3 添加单独的索引，但我的请求工作缓慢。或者也许我可以做一些改变或使用一些其他函数来获得网格结果数组？

大小t_my 50000 行

大小t_my_other 相同的 50000 行

我需要为 Serie1 和 Serie2 的每个组合获取值网格

金额，金额，Serie1，Serie2

EXPLAIN
WITH CTS AS
(
    SELECT * FROM (SELECT 50.0+10.0/11*generate_series(0, 11) as Serie) as tempt CROSS JOIN (SELECT 20.0+25.0/11*generate_series(0, 11) as Serie2) as t
) 

SELECT    COUNT(id) AS amount, SUM(param3) AS wire_guard, CTS.Serie, CTS.Serie2
FROM      CTS 
LEFT JOIN (SELECT t_my.id,t_my.param1,t_my.param2, t_my_other.param3 FROM t_my 
          LEFT JOIN t_my_other ON t_my.id = t_my_other.id_object) as objects 
ON        objects.param1>= CTS.Serie 
AND       objects.param1<  CTS.Serie + (60.0-50)/11
AND       objects.param2>=  CTS.Serie2
AND       objects.param2<  CTS.Serie2 + (35.0-10)/11

GROUP BY  (CTS.Serie, CTS.Serie2)
ORDER BY  CTS.Serie
;
;```

plan
'GroupAggregate  (cost=1617712999.78..1649282408.93 rows=40000 width=80)'
'  Group Key: cts.serie, cts.serie2'
'  CTE cts'
'    ->  Nested Loop  (cost=0.00..12532.53 rows=1000000 width=64)'
'          ->  Result  (cost=0.00..5.01 rows=1000 width=32)'
'          ->  Materialize  (cost=0.00..20.02 rows=1000 width=32)'
'                ->  Result  (cost=0.00..5.01 rows=1000 width=32)'
'  ->  Sort  (cost=1617700467.25..1624014269.08 rows=2525520732 width=76)'
'        Sort Key: cts.serie, cts.serie2'
'        ->  Hash Right Join  (cost=604227963.92..662200918.76 rows=2525520732 width=76)'
'              Hash Cond: (t_my_other.id_object = t_my.id)'
'              ->  Seq Scan on t_my_other (cost=0.00..8501.18 rows=297518 width=12)'
'              ->  Hash  (cost=546125388.00..546125388.00 rows=2399074074 width=72)'
'                    ->  Nested Loop Left Join  (cost=434.15..546125388.00 rows=2399074074 width=72)'
'                          ->  CTE Scan on cts  (cost=0.00..20000.00 rows=1000000 width=64)'
'                          ->  Bitmap Heap Scan on t_my  (cost=434.15..522.12 rows=2399 width=24)'
'                                Recheck Cond: ((param2 >= (cts.serie2)::double precision) AND (param2 < ((cts.serie2 + 2.2727272727272727))::double precision) AND (param1 >= (cts.serie)::double precision) AND (param1 < ((cts.serie + 0.90909090909090909091))::double precision))'
'                                ->  BitmapAnd  (cost=434.15..434.15 rows=2399 width=0)'
'                                      ->  Bitmap Index Scan on i_param2  (cost=0.00..216.35 rows=21592 width=0)'
'                                            Index Cond: ((param2  >= (cts.serie2)::double precision) AND (param2  < ((cts.serie2 + 2.2727272727272727))::double precision))'
'                                      ->  Bitmap Index Scan on i_param1  (cost=0.00..216.35 rows=21592 width=0)'
'                                            Index Cond: ((param1 >= (cts.serie)::double precision) AND (param1  < ((cts.serie + 0.90909090909090909091))::double precision))'

Answer 1

升级到 PostgreSQL v12 或更高版本，因为

该版本引入了优化器支持函数，可以为 generate_series
正确估计行数
从 v12 开始，CTE 不再充当优化障碍

这应该会改进执行计划，从而改进性能。

优化postgresql请求

Optimization postgresql request

sql

postgresql

indexing

optimization

generate-series