sql - 时间间隔的tsrange计算？

我有一张预定房间的桌子：

CREATE TABLE reservation (room int, during tsrange);
INSERT INTO reservation VALUES
    (1108, '[2010-01-01 09:30, 2010-01-01 10:30)');

问题：
我需要得到这个房间剩余的空闲时间间隔：30分钟，45分钟，1小时和1.30分钟在白天（09.00-18.00）。
怎么做？
谢谢大家。

最佳答案

以下查询将返回reservation中有条目的所有天数的所有空闲间隔：

WITH mins(lt) AS (
   /* get all lower bounds of intervals */
   SELECT lower(during)
   FROM reservation
   UNION
   /* get 18:00 for each day */
   SELECT date_trunc('day', lower(during)) + INTERVAL '18 hours'
   FROM reservation
), maxs(ut) AS (
   /* get all upper bounds of intervals */
   SELECT upper(during)
   FROM reservation
   UNION
   /* get 09:00 for each day */
   SELECT date_trunc('day', lower(during)) + INTERVAL '9 hours'
   FROM reservation
)
SELECT tsrange(ut, lt)  /* candidate for a free interval */
FROM mins
   JOIN maxs
      ON date_trunc('day', lt) = date_trunc('day', ut)
         AND ut < lt
/* exclude all such intervals that overlap an entry */
WHERE NOT EXISTS (SELECT 1 FROM reservation
                  WHERE during && tsrange(ut, lt, '()'))
ORDER BY ut;

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