sql—如何更快地搜索包含8000万条记录的表?

goqiplq2  于 2021-07-26  发布在  Java
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我有一个大约有8000万条记录的表,我想找到用户可以访问的列表和工作区的所有活动。因此,首先,我获取列表和工作区的ID,然后运行以下查询:

select *, COALESCE("origin_created_at", "created_at") AS "created_at",
  COALESCE("updated_at", "origin_updated_at") AS "updated_at" 
from "activities" 
where ("listId" in (310,214088,219,220,271,222,28434,36046,43233,38236,
  1014787,1017501,1065915,162,399844,399845,395721,824491,400,405,408,
  395873,36,188,178,120,461,1104,27341,27356,83329,29271,158639,482197,
  587679,841589,722320,551,170392,421035,197071,632736,632742,632755,
  632758,673517,155,1231,2691,2695,9092,13783,24273,45765,57909,57938,
  58323,291171,324525,496,5369,54099,54576,98818,569319,1434677,279,
  158821,127,158197,50301,761351,261,438101,159009,643013,158273,58557,
  643867,356252,631758,299145,131,179,156,661,241,260,281,245,438106,
  886,101,72915,90857,144564,166270,230,178981,195046,208561,382159,
  226599,297964,298318,89043,193559,326394,313589,450540,541359,620442,
  323458,628644,643014,261008,650332,689117,847849,672369,932660,382843,
  267000,826590,642775,400339,642875,1282788,1341992,1411789,1515479,
  74018) 
 or "workspaceId" in (137, 81, 111, 424284, 425935, 430658, 84, 163840, 
  3, 4, 281105, 57, 64642, 96660, 38739, 273574, 295312, 79, 213, 
  240478, 424760, 65, 36989)) 
and (("isBulk" = false or "activities"."type" = 0) 
       and "activities"."deprecated_at" is null) 
order by COALESCE("origin_created_at", "created_at") DESC, "id" desc
limit 40;

这就是执行计划

Limit  (cost=2446886.55..2446886.65 rows=40 width=1002) (actual time=44452.393..44452.418 rows=40 loops=1)
   ->  Sort  (cost=2446886.55..2449439.67 rows=1021250 width=1002) (actual time=44452.391..44452.401 rows=40 loops=1)
         Sort Key: (COALESCE(origin_created_at, created_at)) DESC, id DESC
         Sort Method: top-N heapsort  Memory: 37kB
         ->  Bitmap Heap Scan on activities  (cost=37546.04..2414605.20 rows=1021250 width=1002) (actual time=1043.663..43916.385 rows=568891 loops=1)
               Recheck Cond: (("listId" = ANY ('{310,214088,219,220,271,222,28434,36046,43233,38236,1014787,1017501,1065915,162,399844,399845,395721,824491,400,405,408,395873,36,188,178,120,461,1104,27341,27356,83329,29271,158639,482197,587679,841589,722320,551,170392,421035,197071,632736,632742,632755,632758,673517,155,1231,2691,2695,9092,13783,24273,45765,57909,57938,58323,291171,324525,496,5369,54099,54576,98818,569319,1434677,279,158821,127,158197,50301,761351,261,438101,159009,643013,158273,58557,643867,356252,631758,299145,131,179,156,661,241,260,281,245,438106,886,101,72915,90857,144564,166270,230,178981,195046,208561,382159,226599,297964,298318,89043,193559,326394,313589,450540,541359,620442,323458,628644,643014,261008,650332,689117,847849,672369,932660,382843,267000,826590,642775,400339,642875,1282788,1341992,1411789,1515479,74018}'::integer[])) OR ("workspaceId" = ANY ('{137,81,111,424284,425935,430658,84,163840,3,4,281105,57,64642,96660,38739,273574,295312,79,213,240478,424760,65,36989}'::integer[])))
               Rows Removed by Index Recheck: 9072392
               Filter: ((deprecated_at IS NULL) AND ((NOT "isBulk") OR (type = 0)))
               Rows Removed by Filter: 113630
               Heap Blocks: exact=41259 lossy=271838
               ->  BitmapOr  (cost=37546.04..37546.04 rows=1350377 width=0) (actual time=1032.769..1032.769 rows=0 loops=1)
                     ->  Bitmap Index Scan on activities_list_id_index  (cost=0.00..17333.10 rows=617933 width=0) (actual time=118.412..118.412 rows=507019 loops=1)
                           Index Cond: ("listId" = ANY ('{310,214088,219,220,271,222,28434,36046,43233,38236,1014787,1017501,1065915,162,399844,399845,395721,824491,400,405,408,395873,36,188,178,120,461,1104,27341,27356,83329,29271,158639,482197,587679,841589,722320,551,170392,421035,197071,632736,632742,632755,632758,673517,155,1231,2691,2695,9092,13783,24273,45765,57909,57938,58323,291171,324525,496,5369,54099,54576,98818,569319,1434677,279,158821,127,158197,50301,761351,261,438101,159009,643013,158273,58557,643867,356252,631758,299145,131,179,156,661,241,260,281,245,438106,886,101,72915,90857,144564,166270,230,178981,195046,208561,382159,226599,297964,298318,89043,193559,326394,313589,450540,541359,620442,323458,628644,643014,261008,650332,689117,847849,672369,932660,382843,267000,826590,642775,400339,642875,1282788,1341992,1411789,1515479,74018}'::integer[]))
                     ->  Bitmap Index Scan on activities_workspace_id_index  (cost=0.00..19702.32 rows=732444 width=0) (actual time=914.355..914.355 rows=682628 loops=1)
                           Index Cond: ("workspaceId" = ANY ('{137,81,111,424284,425935,430658,84,163840,3,4,281105,57,64642,96660,38739,273574,295312,79,213,240478,424760,65,36989}'::integer[]))
 Planning time: 2.882 ms
 Execution time: 44452.871 ms
(17 rows)

正如计划中所述,postgresql使用“位图堆扫描”来扫描活动,这使得查询速度变慢,尽管这两个列都被索引。表上总共有4个索引,分别对应于以下列:type、listid、workspaceid、organizationid。
如何使查询更快?还是有更好的方法重写查询?

uelo1irk

uelo1irk1#

正如计划中所述,postgresql使用“位图堆扫描”来扫描活动,这使得查询速度变慢,尽管这两个列都被索引。
它正在使用这两个索引。用于引导堆扫描的位图基于它们,通过位图Map器。
一个可能的罪魁祸首是:

Rows Removed by Index Recheck: 9072392
Heap Blocks: exact=41259 lossy=271838

增加功,直到有损块消失。但如果问题是从磁盘读取数据块的时间,那可能就没用了。

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