如何使用postgres查找事件对? [英] How to find pairs of events with postgres?

问题描述

我有一个事件表:

             ts             |  user  | reason 
----------------------------+--------+--------
 2018-06-01 10:44:15.52+01  | 359999 | START
 2018-06-01 10:44:29.521+01 | 359999 | STOP
 2018-06-01 10:44:43.52+01  | 359998 | START
 2018-06-01 10:44:55.52+01  | 359999 | START
 2018-06-01 10:44:59.521+01 | 359998 | STOP
 2018-06-01 10:45:07.52+01  | 359999 | STOP
 2018-06-01 10:46:16.52+01  | 359999 | START

我想找到事件对:

  user  |           start            |            stop            
--------+----------------------------+----------------------------
 359999 | 2018-06-01 10:44:15.52+01  | 2018-06-01 10:44:29.521+01
 359998 | 2018-06-01 10:44:43.52+01  | 2018-06-01 10:44:59.521+01
 359999 | 2018-06-01 10:44:55.52+01  | 2018-06-01 10:45:07.52+01
 359999 | 2018-06-01 10:46:16.52+01  |

什么样的查询可以做到这一点?

What sort of query could do this?

推荐答案

您可以使用 窗口函数.除其他外，这些允许您引用查询结果中的下一行/上一行(通过 lead() 和 lag()).例如:

You can do this pretty easily with a window function. Among other things, these let you reference the next/previous row in a query result (via lead() and lag()). For example:

SELECT "user", ts AS start, next_ts AS stop
FROM (
  SELECT *, lead(ts) OVER (PARTITION BY "user" ORDER BY ts) AS next_ts
  FROM events
  WHERE reason IN ('START', 'STOP')
) AS ts_pairs
WHERE reason = 'START'

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