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如何使用mongodb中的条件获取数组的最后一个元素.我无法使用切片.这是我的代码

{ "1" : { "relevancy" : [  "Y" ] }, "_id" : ObjectId("530824b95f44eac1068b45c0") }
{ "1" : { "relevancy" : [  "Y",  "Y" ] }, "_id" : ObjectId("530824b95f44eac1068b45c2") }
{ "1" : { "relevancy" : [  "N" ] }, "_id" : ObjectId("530824b95f44eac1068b45c3") }
{ "1" : { "relevancy" : [  "Y",  "Y" ] }, "_id" : ObjectId("530824b95f44eac1068b45c4") }
{ "1" : { "relevancy" : [  "Y",  "N" ] }, "_id" : ObjectId("530824b95f44eac1068b45c6") }
{ "1" : { "relevancy" : …

我有一个案例,我想查询在数组字段"窗体"下有许多项目的文档集合.要解决的问题是希望仅返回具有"窗体"中包含的所有文档的文档,其特定状态为"已关闭".

所以这里是集合中两个不同文档的示例:

{
    "_id" : "Tvq444454j",
    "name" : "Jim",
    "forms" : [
        {
            "name" : "Jorney",
            "status" : "closed"
        },
        {
            "name" : "Women",
            "status" : "void"
        },
        {
            "name" : "Child",
            "status" : "closed"
        },
        {
            "name" : "Farm",
            "status" : "closed"
        }
    ]
},

{
    "_id" : "Tvq579754r",
    "name" : "Tom",
    "forms" : [
        {
            "name" : "PreOp",
            "status" : "closed"
        },
        {
            "name" : "Alert",
            "status" : "closed"
        },
        {
            "name" : "City", …