25

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

我想禁止给定的重叠间隔(account_id, product_id)

编辑：我发现了一些东西：

CREATE TABLE test (                                                                                                
    from_ts TIMESTAMPTZ,
    to_ts TIMESTAMPTZ,
    account_id INTEGER,
    product_id INTEGER,
    CHECK ( from_ts < to_ts ),
    CONSTRAINT overlapping_times EXCLUDE USING GIST (
        account_id WITH =,
        product_id WITH =,
        box(
            point( extract(epoch FROM from_ts at time zone 'UTC'), extract(epoch FROM from_ts at time zone 'UTC') ),
            point( extract(epoch FROM to_ts at time zone 'UTC') , extract(epoch FROM to_ts at time zone 'UTC') )
        ) WITH &&
    )
);

如果您想了解更多关于此http://www.depesz.com/2010/01/03/waiting-for-8-5-exclusion-constraints/

我唯一的问题是它不能使用空值作为结束时间戳，我想用无限值替换它但效果不佳。

4

4 回答 4

29

好的，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、交易证明完美结合。

我只需要安装临时扩展，它将在 postgres 9.2 中本地化，并且 btree_gist 在 9.1 中作为扩展可用CREATE EXTENSION btree_gist;

注意：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。

于 2012-05-21T10:17:31.930 回答
7

在最新的 postgres 版本中（我在 9.6 中对其进行了测试，但我认为它在 >=9.2 中工作）您可以使用tstzrange()其他评论中提到的内置功能。默认情况下，空值将被视为正无穷大或负无穷大，然后不再明确需要 CHECK 约束（如果您认为仅检查<=并且范围可以以相同日期开始和结束）。只需要扩展名btree_gist：

CREATE 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 &&
    )
);
于 2017-10-05T07:46:53.387 回答
0

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NOT EXISTS()在检查中添加一些子查询）

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，也不能引用当前行列以外的变量。

流行的解决方法是：使用执行脏工作的触发器函数（或使用大多数人不赞成使用的规则系统）

因为大多数人都喜欢触发器，所以我将在这里重新发布一个规则系统黑客......（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;
于 2012-05-16T10:50:20.613 回答
-4

如何为一组列创建唯一约束：

 CREATE TABLE table (
    date_start date,
    date_end  date,
    account_id integer,
    UNIQUE (account_id , date_start ,date_end) );

在您的情况下，如果表已经存在，您将需要 ALTER TABLE，请查看对您有帮助的文档：
-DDL约束
-ALTER Table

于 2012-05-16T10:04:30.743 回答