我有一张这样的桌子：
date_start date_end account_id product_id
2001-01-01 2001-01-31 1 1
2001-02-01 2001-02-20 1 1
2001-04-01 2001-05-20 1 1
我想禁止给定的间隔重叠
(account_id, product_id)好吧，我最终这样做了：
CREATE TABLE test (
from_ts TIMESTAMPTZ,
to_ts TIMESTAMPTZ,
account_id INTEGER DEFAULT 1,
product_id INTEGER DEFAULT 1,
CHECK ( from_ts < to_ts ),
CONSTRAINT overlapping_times EXCLUDE USING GIST (
account_id WITH =,
product_id WITH =,
period(from_ts, CASE WHEN to_ts IS NULL THEN 'infinity' ELSE to_ts END) WITH &&
)
);
与无穷大、交易证明完美配合。
我只需要安装临时扩展，该扩展将在 postgres 9.2 中原生，而 btree_gist 可作为 9.1 中的扩展
CREATE EXTENSION btree_gist;nb：如果您没有空时间戳，则无需使用时间扩展，您可以使用我的问题中指定的 box 方法。
在最新的 postgres 版本中（我在 9.6 中测试了它，但我假设它在 >=9.2 中工作），您可以使用内置函数
tstzrange()<=btree_gistCREATE EXTENSION btree_gist;
CREATE TABLE test (
from_ts TIMESTAMPTZ,
to_ts TIMESTAMPTZ,
account_id INTEGER DEFAULT 1,
product_id INTEGER DEFAULT 1,
CONSTRAINT overlapping_times EXCLUDE USING GIST (
account_id WITH =,
product_id WITH =,
TSTZRANGE(from_ts, to_ts) WITH &&
)
);
这是一个难题，因为约束只能引用“当前行”，并且可能不包含子查询。 （否则简单的解决方案是在检查中添加一些
NOT EXISTS()指定为列约束的检查约束应仅引用该列的值，而出现在表约束中的表达式可以引用多个列。
目前，CHECK 表达式不能包含子查询，也不能引用除当前行的列以外的变量。
流行的解决方法是：使用触发函数来完成肮脏的工作（或使用大多数人不赞成的规则系统）
因为大多数人都喜欢触发器，所以我将在这里重新发布规则系统黑客......（它没有额外的“id”关键元素，但这是一个小细节）
-- Implementation of A CONSTRAINT on non-overlapping datetime ranges
-- , using the Postgres rulesystem.
-- We need a shadow-table for the ranges only to avoid recursion in the rulesystem.
-- This shadow table has a canary variable with a CONSTRAINT (value=0) on it
-- , and on changes to the basetable (that overlap with an existing interval)
-- an attempt is made to modify this variable. (which of course fails)
-- CREATE SCHEMA tmp;
DROP table tmp.dates_shadow CASCADE;
CREATE table tmp.dates_shadow
( time_begin timestamp with time zone
, time_end timestamp with time zone
, overlap_canary INTEGER NOT NULL DEFAULT '0' CHECK (overlap_canary=0)
)
;
ALTER table tmp.dates_shadow
ADD PRIMARY KEY (time_begin,time_end)
;
DROP table tmp.dates CASCADE;
CREATE table tmp.dates
( time_begin timestamp with time zone
, time_end timestamp with time zone
, payload varchar
)
;
ALTER table tmp.dates
ADD PRIMARY KEY (time_begin,time_end)
;
CREATE RULE dates_i AS
ON INSERT TO tmp.dates
DO ALSO (
-- verify shadow
UPDATE tmp.dates_shadow ds
SET overlap_canary= 1
WHERE (ds.time_begin, ds.time_end) OVERLAPS ( NEW.time_begin, NEW.time_end)
;
-- insert shadow
INSERT INTO tmp.dates_shadow (time_begin,time_end)
VALUES (NEW.time_begin, NEW.time_end)
;
);
CREATE RULE dates_d AS
ON DELETE TO tmp.dates
DO ALSO (
DELETE FROM tmp.dates_shadow ds
WHERE ds.time_begin = OLD.time_begin
AND ds.time_end = OLD.time_end
;
);
CREATE RULE dates_u AS
ON UPDATE TO tmp.dates
WHERE NEW.time_begin <> OLD.time_begin
AND NEW.time_end <> OLD.time_end
DO ALSO (
-- delete shadow
DELETE FROM tmp.dates_shadow ds
WHERE ds.time_begin = OLD.time_begin
AND ds.time_end = OLD.time_end
;
-- verify shadow
UPDATE tmp.dates_shadow ds
SET overlap_canary= 1
WHERE (ds.time_begin, ds.time_end) OVERLAPS ( NEW.time_begin, NEW.time_end)
;
-- insert shadow
INSERT INTO tmp.dates_shadow (time_begin,time_end)
VALUES (NEW.time_begin, NEW.time_end)
;
);
INSERT INTO tmp.dates(time_begin,time_end) VALUES
('2011-09-01', '2011-09-10')
, ('2011-09-10', '2011-09-20')
, ('2011-09-20', '2011-09-30')
;
SELECT * FROM tmp.dates;
EXPLAIN ANALYZE
INSERT INTO tmp.dates(time_begin,time_end) VALUES ('2011-09-30', '2011-10-04')
;
INSERT INTO tmp.dates(time_begin,time_end) VALUES ('2011-09-02', '2011-09-04')
;
SELECT * FROM tmp.dates;
SELECT * FROM tmp.dates_shadow;