Question

我有一张这样的表：

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(account_id, product_id)

的重叠间隔编辑：我找到了一些东西：

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 &&
    )
);

如果您想了解有关此http://www.depesz.com/2010/01/03/waiting-for-8-5-exclusion-constraints/

的更多信息

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是不能正常工作。

Answer 1

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 &&
    )
);

与无限，交易证明完美配合。

我只需要安装时间扩展，这将在postgres 9.2中生成，btree_gist可用作9.1 CREATE EXTENSION btree_gist;

中的扩展名

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。

Answer 2

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＆gt; = 9.2中工作），您可以使用其他一些注释中提到的构建函数tstzrange()。默认情况下，空值将被视为正无穷大或负无穷大，因此不再明确需要CHECK约束（如果您可以检查<=并且范围可以以相同日期开始和结束）。只需要扩展程序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 &&
    )
);

Answer 3

这是一个难题，因为constraints can only reference the "current row"，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()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，也不能引用当前行的列以外的变量。

流行的解决方法是：使用执行脏工作的触发器功能（或使用大多数人不推荐使用的规则系统）

因为大多数人喜欢触发器，我会在这里重新发布一个规则系统hack ...（它没有额外的“id”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;

Answer 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，如果表格已经存在，您将需要ALTER TABLE，请查看对您有帮助的文档：
- DDL Constraints
- ALTER Table

Postgres日期重叠约束

4 个答案: