根据时间间隔拆分 table 数据

Question

假设我们有一个导入到 postgres 中的实体元数据的时间序列数据集 table Stats:

CREATE EXTENSION IF NOT EXISTS POSTGIS;
DROP TABLE IF EXISTS "Stats";
CREATE TABLE IF NOT EXISTS "Stats"
(
    "time" BIGINT,
    "id" BIGINT,
    "position" GEOGRAPHY(PointZ, 4326)
);

这里是 table 的示例：

SELECT 
    "id",
    "time"
FROM
    "Stats"
ORDER BY 
    "id", "time" ASC

id|time|
--+----+
 1|   3|
 1|   4|
 1|   6|
 1|   7|
 2|   2|
 2|   6|
 3|  14|
 4|   2|
 4|   9|
 4|  10|
 4|  11|
 5|  32|
 6|  15|
 7|  16|

业务需求是给这个table中的实体分配route-id，所以当每个实体的时间跳过1 second时，就意味着该实体的新航班或航线。之前的样本的最终结果如下：

id|time|route_id|
--+----+--------+
 1|   3|       1|
 1|   4|       1|
 1|   6|       2|
 1|   7|       2|
 2|   2|       1|
 2|   6|       2|
 3|  14|       1|
 4|   2|       1|
 4|   9|       2|
 4|  10|       2|
 4|  11|       2|
 5|  32|       1|
 6|  15|       1|
 7|  16|       1|

这将是路线的新摘要 table：

id|start_time|end_time|route_id|
--+----------+--------+--------+
 1|         3|       4|       1|
 1|         6|       7|       2|
 2|         2|       2|       1|
 2|         6|       6|       2|
 3|        14|      14|       1|
 4|         2|       2|       1|
 4|         9|      11|       2|
 5|        32|      32|       1|
 6|        15|      15|       1|
 7|        16|      16|       1|

那么应该如何构建这个复杂的查询？

Answer 1

with data as (
    select *, row_number() over (partition by id order by "time") rn from Stats
)
select id,
    min("time") as start_time, max("time") as end_time,
    row_number() over (partition by id order by "time" - rn) as route_id
from data
group by id, "time" - rn
order by id, "time" - rn

https://dbfiddle.uk/?rdbms=postgres_9.5&fiddle=c272bc57786487b0b664648139530ae4

Answer 2

假设您手头有 table stats，以下查询将通过分配 route_id:

创建一个 table

查询分配 route_id 使用 recursive-cte:

CREATE TABLE tbl_route AS 
with recursive cte AS 
(
  SELECT id,  prev_time, time, rn, rn AS ref_rn, rn AS route_id 
  FROM 
  (    
    SELECT 
      *,
      lag(time) OVER(partition BY id ORDER BY time) AS prev_time,
      row_number() OVER(partition BY id ORDER BY time) AS rn 
    FROM stats
  ) AS rnt
  WHERE rn=1

  UNION

  SELECT rnt2.id, rnt2.prev_time, rnt2.time, rnt2.rn, cte.rn AS ref_rn,
    CASE 
      WHEN abs(rnt2.time-rnt2.prev_time)<=1 THEN cte.route_id
      ELSE cte.route_id+1
    END AS route_id
  FROM cte
  INNER JOIN
  (
   SELECT 
     *,
     lag(time) OVER(partition BY id ORDER BY time) AS prev_time,
     row_number() OVER(partition BY id ORDER BY time) AS rn 
   FROM stats
  ) AS rnt2
   ON cte.id=rnt2.id AND cte.rn+1 = rnt2.rn
)

SELECT id, time, route_id FROM cte;

查询以检查 route_id 分配是否正确：

select id, time, route_id 
from tbl_route 
order by id, time

要创建的查询 new summary table:

select id, min(time) as start_time, max(time) as end_time, route_id
from tbl_route
group by id, route_id
order by id, route_id, start_time, end_time

递归 CTE 查询细分：

由于使用了recursive cte，查询可能看起来比较乱。但是，我尝试将其分解如下：

有 2 个主要查询使用 UNION 附加，第一个将为每个 id 的开头分配 route_id，第二个将为每个 id 的其余行执行此操作
rnt 和 rnt2 已创建，因为我们需要 ROW_NUMBER 和 LAG 值来实现此
我们加入了cte和rnt2recursively通过检查时间的差异分配route_id

DEMO

根据时间间隔拆分 table 数据

Split table data based on time gaps

sql

postgresql

postgis

window-functions