Question

I want to have a table, where I want to have entries, which are date ranged. How I normally did it, was to have a table with: someId [not unique] startDate endDate

这三个方面将形成一个主要的关键会议。我要补充几点限制,以确保日期不会重叠等。

Everything is fine from the database point of view, however when I want to create a domain class in Grails to handle it... well it s more difficult then I thought. Is there a way, to make sure that if I have a relation: ClassA hasOne ClassB [ClassB would be date ranged] and I have entries in ClassB:

Id  StartDate  EndDate     Name
1   2011-11-01 2011-11-05  A
1   2011-11-06 2011-11-10  B

标题 B号为A,2011-11-03年,然后在2011-11-07年检索物体A。

Answer 1

What we did in the end was: create index and constraint on the three columns [on the database, since creating indexes in Grails 1.3.7 is broken and constraint handling is insane], created static startDate and endDate variables which hold start and end date of the current range. This way we were able to maintain the functionality we wanted and it performs really well.

Answer 2

That seems like a poor way to design your database. In most cases, you really should just use a single numeric ID for objects.

如果你处理与同一目标有多个日期范围的情况,那么你就应当安排数据,以代表母物体和代表日期范围清单的儿童物体。

class Foo {
    static hasMany = [bars:Bar]
    static mapping = {
        bars lazy:false
    }
    ...
}

class Bar {
    static belongsTo = [foo:Foo]
    Date startDate
    Date endDate
    ...
}

铁路公司确实很简单,可以删除铁路,因此没有真正的理由不这样做。

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