sql - 每周总计唯一序列号

Question

我正在尝试编写一个查询来搜索我的数据库并每周查找设备的唯一序列号总数。我当前的代码是:

SELECT date_part('week', "timestamp") , count(DISTINCT serialno) 
FROM eddi_minute em 
GROUP BY date_part('week', "timestamp")  

不幸的是，我正在搜索的数据集很大 (~600Gb)，因此搜索时间非常长。我希望能够每周搜索一次，每周搜索一次很短的时间，即 1 分钟 a.k.a.

select count(distinct serialno) as Devices
        from eddi_minute em where "timestamp" >= '2021-06-23 00:01:00' and "timestamp" < '2021-06-23 00:02:00';

但是对于一整年的每个星期，这样我就可以按一次回车键，它会为整个数据库执行此操作，以避免不必要的计数。

在理想情况下，我的想法是创建一个我要搜索的时间表，然后用它和我的数据库进行左连接以减少我正在搜索的数据，但我只有读取权限到服务器，所以这不是一个选项。有没有简单的方法可以做到这一点？抱歉，如果这里有任何不清楚的地方，如果有任何地方没有得到正确解释，我会详细说明。

表的索引是

CREATE UNIQUE INDEX "PK_4c94f05e4de575488f4a0c2905d" ON ONLY public.eddi_minute USING btree (serialno, "timestamp")

解释分析结果是:

GroupAggregate  (cost=41219561.55..90787854.96 rows=200 width=16) (actual time=7065790.406..8172419.446 rows=53 loops=1)
  Group Key: (date_part('week'::text, em."timestamp"))
  ->  Gather Merge  (cost=41219561.55..88747442.16 rows=408082059 width=16) (actual time=7052726.256..7834672.575 rows=408057194 loops=1)
        Workers Planned: 2
        Workers Launched: 2
        ->  Sort  (cost=41218561.53..41643646.99 rows=170034187 width=16) (actual time=6956066.331..7201252.404 rows=136019065 loops=3)
              Sort Key: (date_part('week'::text, em."timestamp"))
              Sort Method: external merge  Disk: 3368720kB
              Worker 0:  Sort Method: external merge  Disk: 3640792kB
              Worker 1:  Sort Method: external merge  Disk: 3371808kB
              ->  Parallel Append  (cost=0.00..9256242.79 rows=170034187 width=16) (actual time=0.435..2825202.379 rows=136019065 loops=3)
                    ->  Parallel Seq Scan on eddi_minute_p2021_05 em_11  (cost=0.00..1725776.58 rows=34898767 width=16) (actual time=0.011..1722528.987 rows=83740195 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_06 em_12  (cost=0.00..1488905.33 rows=30102507 width=16) (actual time=1.266..1488189.219 rows=72252984 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_04 em_10  (cost=0.00..1428581.36 rows=28905149 width=16) (actual time=149.934..1290294.249 rows=69366177 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_03 em_9  (cost=0.00..1290438.50 rows=26110040 width=16) (actual time=69.475..483281.530 rows=20887814 loops=3)
                    ->  Parallel Seq Scan on eddi_minute_p2021_02 em_8  (cost=0.00..922294.02 rows=18661202 width=16) (actual time=195.734..931653.840 rows=44786882 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_01 em_7  (cost=0.00..823415.96 rows=16660557 width=16) (actual time=102.708..834900.144 rows=39985282 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2020_12 em_6  (cost=0.00..293130.95 rows=5931036 width=16) (actual time=182.465..296634.818 rows=14234537 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2020_11 em_5  (cost=0.00..111271.35 rows=2251388 width=16) (actual time=195.367..110910.685 rows=5403366 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2020_10 em_4  (cost=0.00..105311.10 rows=2130808 width=16) (actual time=146.920..109340.586 rows=5113938 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2020_09 em_3  (cost=0.00..93692.39 rows=1895711 width=16) (actual time=87.456..94169.812 rows=4549714 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2020_08 em_2  (cost=0.00..86189.97 rows=1743918 width=16) (actual time=0.007..88029.891 rows=4185403 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2020_07 em_1  (cost=0.00..33400.45 rows=675796 width=16) (actual time=1.046..14190.279 rows=1621911 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_07 em_13  (cost=0.00..3438.66 rows=88773 width=16) (actual time=0.006..51.229 rows=150887 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_default em_26  (cost=0.00..45.20 rows=1456 width=16) (actual time=0.016..0.639 rows=2477 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_08 em_14  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_09 em_15  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.515 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_10 em_16  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_11 em_17  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2021_12 em_18  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2022_01 em_19  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2022_02 em_20  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2022_03 em_21  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.001 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2022_04 em_22  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2022_05 em_23  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2022_06 em_24  (cost=0.00..15.00 rows=400 width=16) (actual time=0.000..0.000 rows=0 loops=1)
                    ->  Parallel Seq Scan on eddi_minute_p2022_07 em_25  (cost=0.00..15.00 rows=400 width=16) (actual time=0.002..0.003 rows=0 loops=1)
Planning Time: 35.809 ms
Execution Time: 8172556.078 ms

Answer 1

一些想法:

尽管"timestamp"是有效的列名，为对象使用保留名称被认为是不好的做法。它可能看起来无害，但从长远来看会变得非常烦人。

我相信列中的索引 "timestamp"应该显着提高第二个查询的性能:

CREATE INDEX idx_timestamp ON eddi_minute ("timestamp");

关于第一个查询:考虑到您有一个 600GB (!) 的表，创建 partial index 可能会很有趣在 "timestamp" 栏中, 以便时间戳按您将在查询中使用的值编制索引，例如周:

CREATE INDEX idx_timestamp_week ON eddi_minute (date_part('week', "timestamp"));

注意:虽然索引可以加快查询速度，但它们会减慢其他操作的速度，例如插入、更新和删除。如果您创建新索引，请测试所有相关操作的性能。

演示: db<>fiddle