在嵌套数组中查找匹配条件的第一个元素 [英] Find first element in nested array that match conditions

问题描述

我有以下文件:

doc1: { 
  'array': [
    {'field': 'ABC', 'enabled': 'false'},
    {'field': 'BCD', 'enabled': 'true'},
    {'field': 'DEF', 'enabled': 'false'},
    {'field': 'XYZ', 'enabled': 'true'},
  ]
}


doc2: { 
  'array': [
    {'field': 'ABC', 'enabled': 'true'},
    {'field': 'BCD', 'enabled': 'true'},
    {'field': 'DEF', 'enabled': 'false'},
    {'field': 'XYZ', 'enabled': 'true'},
  ]
}

我正在按特定领域进行搜索. 我想获取所有启用了此字段的文档，并且在此之前(列表中)没有启用其他字段.

I'm performing search by particular field. I want to get all documents that have this field enabled, and there are no other fields enabled before this (in the list).

例如:

搜索字段:BCD，已启用:true-应该仅返回第一个文档(因为第二个文档ABC也已启用).

search for field: BCD, enabled: true - should return only first document (because in second document ABC is enabled too).

搜索XYZ，已启用:true-完全不应该返回任何文档，因为此列表顶部还启用了其他字段.

search for XYZ, enabled: true - should not return any documents at all, because there are other fields enabled on top of this list.

我试图对$elemMatch做某事，但是我不知道是否有可能在elemMatch匹配的元素之上应用过滤器.

I was trying to do smth with $elemMatch, but I don't know if it's possible to apply filter on top of element that elemMatch has matched.

有什么建议吗?

推荐答案

有$where关键字允许出于类似目的生成复杂的条件.

There is $where keyword that allow to generate complex conditions for similar purpose.

find($where: 'this.array.filter(function(e){return e.enabled=="true"})[0].field=="ABC"')

由于它不使用任何索引，因此我将添加更多条件以从优化中受益.

As this does not use any indexes, I'll add more conditions to benefit from optimisation.

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