相关的前一个问题:
按值(而不是列)分组后从组中选择随机条目? https://stackoverflow.com/questions/15091363/select-a-random-entry-from-a-group-after-grouping-by-a-value-not-column
我当前的查询如下所示:
WITH
points AS (
SELECT unnest(array_of_points) AS p
),
gtps AS (
SELECT DISTINCT ON(points.p)
points.p, m.groundtruth
FROM measurement m, points
WHERE st_distance(m.groundtruth, points.p) < distance
ORDER BY points.p, RANDOM()
)
SELECT DISTINCT ON(gtps.p, gtps.groundtruth, m.anchor_id)
m.id, m.anchor_id, gtps.groundtruth, gtps.p
FROM measurement m, gtps
ORDER BY gtps.p, gtps.groundtruth, m.anchor_id, RANDOM()
语义:
-
有两个输入值:
- 第 4 行:点数组
array_of_points
- 第 12 行:双精度数:
distance
-
第一段(第 1-6 行):
-
第二段(第 8-14 行):
- 对于内的每个点
points
表:获取一个随机数(!)groundtruth
点从measurement
表,其距离 distance
- 将这些元组保存在
gtps
table
-
第三段(第 16-19 行):
- 对于每个
groundtruth
里面的值gtps
表:获取全部anchor_id
价值观和...
- If an
anchor_id
值不唯一:然后随机选择一个
Output: id
, anchor_id
, groundtruth
, p
(输入值来自array_of_points
)
示例表:
id | anchor_id | groundtruth | data
-----------------------------------
1 | 1 | POINT(1 4) | ...
2 | 3 | POINT(1 4) | ...
3 | 8 | POINT(1 4) | ...
4 | 6 | POINT(1 4) | ...
-----------------------------------
5 | 2 | POINT(3 2) | ...
6 | 4 | POINT(3 2) | ...
-----------------------------------
7 | 1 | POINT(4 3) | ...
8 | 1 | POINT(4 3) | ...
9 | 6 | POINT(4 3) | ...
10 | 7 | POINT(4 3) | ...
11 | 3 | POINT(4 3) | ...
-----------------------------------
12 | 1 | POINT(6 2) | ...
13 | 5 | POINT(6 2) | ...
结果示例:
id | anchor_id | groundtruth | p
-----------------------------------------
1 | 1 | POINT(1 4) | POINT(1 0)
2 | 3 | POINT(1 4) | POINT(1 0)
4 | 6 | POINT(1 4) | POINT(1 0)
3 | 8 | POINT(1 4) | POINT(1 0)
5 | 2 | POINT(3 2) | POINT(2 2)
6 | 4 | POINT(3 2) | POINT(2 2)
1 | 1 | POINT(1 4) | POINT(4 8)
2 | 3 | POINT(1 4) | POINT(4 8)
4 | 6 | POINT(1 4) | POINT(4 8)
3 | 8 | POINT(1 4) | POINT(4 8)
12 | 1 | POINT(6 2) | POINT(7 3)
13 | 5 | POINT(6 2) | POINT(7 3)
1 | 1 | POINT(4 3) | POINT(9 1)
11 | 3 | POINT(4 3) | POINT(9 1)
9 | 6 | POINT(4 3) | POINT(9 1)
10 | 7 | POINT(4 3) | POINT(9 1)
如你看到的:
- 每个输入值可以有多个相等的
groundtruth
values.
- 如果一个输入值有多个
groundtruth
值,这些必须全部相等。
- 每个真实输入点元组都与每个可能的
anchor_id
为了这个事实。
- 两个不同的输入值可以有相同的对应
groundtruth
value.
- 两个不同的 groundtruth-inputPoint-tuples 可以具有相同的
anchor_id
- 两个相同的真实输入点元组必须具有不同的
anchor_id
s
基准测试(对于两个输入值):
- 第 1-6 行:16ms
- 第 8-14 行:48ms
- 第 16-19 行:600ms
详细解释:
Unique (cost=11119.32..11348.33 rows=18 width=72)
Output: m.id, m.anchor_id, gtps.groundtruth, gtps.p, (random())
CTE points
-> Result (cost=0.00..0.01 rows=1 width=0)
Output: unnest('{0101000000EE7C3F355EF24F4019390B7BDA011940:01010000003480B74082FA44402CD49AE61D173C40}'::geometry[])
CTE gtps
-> Unique (cost=7659.95..7698.12 rows=1 width=160)
Output: points.p, m.groundtruth, (random())
-> Sort (cost=7659.95..7679.04 rows=7634 width=160)
Output: points.p, m.groundtruth, (random())
Sort Key: points.p, (random())
-> Nested Loop (cost=0.00..6565.63 rows=7634 width=160)
Output: points.p, m.groundtruth, random()
Join Filter: (st_distance(m.groundtruth, points.p) < m.distance)
-> CTE Scan on points (cost=0.00..0.02 rows=1 width=32)
Output: points.p
-> Seq Scan on public.measurement m (cost=0.00..535.01 rows=22901 width=132)
Output: m.id, m.anchor_id, m.tag_node_id, m.experiment_id, m.run_id, m.anchor_node_id, m.groundtruth, m.distance, m.distance_error, m.distance_truth, m."timestamp"
-> Sort (cost=3421.18..3478.43 rows=22901 width=72)
Output: m.id, m.anchor_id, gtps.groundtruth, gtps.p, (random())
Sort Key: gtps.p, gtps.groundtruth, m.anchor_id, (random())
-> Nested Loop (cost=0.00..821.29 rows=22901 width=72)
Output: m.id, m.anchor_id, gtps.groundtruth, gtps.p, random()
-> CTE Scan on gtps (cost=0.00..0.02 rows=1 width=64)
Output: gtps.p, gtps.groundtruth
-> Seq Scan on public.measurement m (cost=0.00..535.01 rows=22901 width=8)
Output: m.id, m.anchor_id, m.tag_node_id, m.experiment_id, m.run_id, m.anchor_node_id, m.groundtruth, m.distance, m.distance_error, m.distance_truth, m."timestamp"
解释分析:
Unique (cost=11119.32..11348.33 rows=18 width=72) (actual time=548.991..657.992 rows=36 loops=1)
CTE points
-> Result (cost=0.00..0.01 rows=1 width=0) (actual time=0.004..0.011 rows=2 loops=1)
CTE gtps
-> Unique (cost=7659.95..7698.12 rows=1 width=160) (actual time=133.416..146.745 rows=2 loops=1)
-> Sort (cost=7659.95..7679.04 rows=7634 width=160) (actual time=133.415..142.255 rows=15683 loops=1)
Sort Key: points.p, (random())
Sort Method: external merge Disk: 1248kB
-> Nested Loop (cost=0.00..6565.63 rows=7634 width=160) (actual time=0.045..46.670 rows=15683 loops=1)
Join Filter: (st_distance(m.groundtruth, points.p) < m.distance)
-> CTE Scan on points (cost=0.00..0.02 rows=1 width=32) (actual time=0.007..0.020 rows=2 loops=1)
-> Seq Scan on measurement m (cost=0.00..535.01 rows=22901 width=132) (actual time=0.013..3.902 rows=22901 loops=2)
-> Sort (cost=3421.18..3478.43 rows=22901 width=72) (actual time=548.989..631.323 rows=45802 loops=1)
Sort Key: gtps.p, gtps.groundtruth, m.anchor_id, (random())"
Sort Method: external merge Disk: 4008kB
-> Nested Loop (cost=0.00..821.29 rows=22901 width=72) (actual time=133.449..166.294 rows=45802 loops=1)
-> CTE Scan on gtps (cost=0.00..0.02 rows=1 width=64) (actual time=133.420..146.753 rows=2 loops=1)
-> Seq Scan on measurement m (cost=0.00..535.01 rows=22901 width=8) (actual time=0.014..4.409 rows=22901 loops=2)
Total runtime: 834.626 ms
实时运行时,应使用大约 100-1000 个输入值运行。所以目前需要 35 到 350 秒,这还远远不够。
我已经尝试删除RANDOM()
功能。这将运行时间(对于 2 个输入值)从大约 670 毫秒减少到大约 530 毫秒。所以这不是目前的主要影响。
如果更容易/更快,也可以运行 2 或 3 个单独的查询并在软件中执行某些部分(它在 Ruby on Rails 服务器上运行)。例如随机选择?!
工作正在进行中:
SELECT
m.groundtruth, ps.p, ARRAY_AGG(m.anchor_id), ARRAY_AGG(m.id)
FROM
measurement m
JOIN
(SELECT unnest(point_array) AS p) AS ps
ON ST_DWithin(ps.p, m.groundtruth, distance)
GROUP BY groundtruth, ps.p
通过这个查询,速度非常快(15ms),但还遗漏了很多:
- 我只需要每个随机行
ps.p
- 这两个数组属于彼此。意思是:里面物品的顺序很重要!
- 这两个数组需要被过滤(随机):
对于每个anchor_id
在出现多次的数组中:保留随机一个并删除所有其他。这也意味着删除相应的id
来自id
-每个删除的数组anchor_id
如果anchor_id
and id
可以存储在元组数组中。例如:{[4,1],[6,3],[4,2],[8,5],[4,4]}
(约束:每个元组都是唯一的,每个 id (==示例中的第二个值)都是唯一的,anchor_ids 不是唯一的)。此示例显示不带仍必须应用的过滤器的查询。应用过滤器后,它看起来像这样{[6,3],[4,4],[8,5]}
.
正在进行的工作二:
SELECT DISTINCT ON (ps.p)
m.groundtruth, ps.p, ARRAY_AGG(m.anchor_id), ARRAY_AGG(m.id)
FROM
measurement m
JOIN
(SELECT unnest(point_array) AS p) AS ps
ON ST_DWithin(ps.p, m.groundtruth, distance)
GROUP BY ps.p, m.groundtruth
ORDER BY ps.p, RANDOM()
现在这给出了非常好的结果并且仍然非常快:16ms
还剩下一件事要做:
-
ARRAY_AGG(m.anchor_id)
已经是随机的,但是:
- 它包含很多重复的条目,因此:
- 我想在上面使用类似 DISTINCT 的东西,but:
- 它必须与同步
ARRAY_AGG(m.id)
。这意味着:
如果 DISTINCT 命令保留索引 1、4 和 7anchor_id
数组,那么它还必须保留数组的索引 1、4 和 7id
数组(当然删除所有其他数组)