我当前正在使用MonGODB v2.6.4的原因除Robomongo尚不支持MongoDB v3.0之外没有其他原因。
使用以下示例文档,如果这不是我要尝试做的精简示例,那我将不怎么构造它们。
db.visitors.insert({
"visits" : [{"building" : "building01", "lastVisit" : new ISODate("2015-02-01 17:05:00")},
{"building" : "building02", "lastVisit" : new ISODate("2015-02-04 04:25:00")},
{"building" : "building03", "lastVisit" : new ISODate("2015-02-07 15:45:00")},
{"building" : "building04", "lastVisit" : new ISODate("2015-02-10 15:45:00")}
],
"firstName" : "John",
"lastName" : "Smith",
"gender" : "male",
"accountNumber" : "123456789",
});
db.visitors.insert({
"visits" : [{"building" : "building01", "lastVisit" : new ISODate("2015-02-02 17:05:00")},
{"building" : "building02", "lastVisit" : new ISODate("2015-02-05 04:25:00")},
{"building" : "building03", "lastVisit" : new ISODate("2015-02-08 15:45:00")},
{"building" : "building04", "lastVisit" : new ISODate("2015-02-11 15:45:00")}
],
"firstName" : "Jane",
"lastName" : "Smith",
"gender" : "female",
"accountNumber" : "987654321",
});
db.visitors.insert({
"visits" : [{"building" : "building01", "lastVisit" : new ISODate("2015-02-03 17:05:00")},
{"building" : "building02", "lastVisit" : new ISODate("2015-02-06 04:25:00")},
{"building" : "building03", "lastVisit" : new ISODate("2015-02-09 15:45:00")},
{"building" : "building04", "lastVisit" : new ISODate("2015-02-12 15:45:00")}
],
"firstName" : "James",
"lastName" : "Smith",
"gender" : "male",
"accountNumber" : "123056780",
});
我想找到特定建筑物的最后一位访客,并且需要该访客返回的整个文档。
我已经解决了这个聚合查询,几乎可以实现我想要的功能:
db.visitors.aggregate([
{$match: {"visits.building": "building02"}},
{$unwind: "$visits"},
{$project: {"visitorId": "$_id", "building": "$visits.building", "lastVisit": "$visits.lastVisit"}},
{$sort: {"lastVisit": 1}},
{$group: {"_id": "$building", "visitorId": {$last: "$visitorId"}, "lastVisit": {$last: "$lastVisit"}}},
{$match: {"_id": "building02"}},
{$limit: 1}
])
并返回以下结构:
{
"result" : [
{
"_id" : "building02",
"visitorId" : ObjectId("55098990ca5b44f2858f4cb5"),
"lastVisit" : ISODate("2015-02-12T15:45:00.000000:00")
}
],
"ok" : 1.0000000000000000
}
如何修改聚合查询以返回整个访问者文档,而不仅是visitorId?我已经尝试过(但使用$$ROOT
和失败$$CURRENT
)。
如果无法返回整个文档,该如何对返回的结果结构进行查找,以便可以通过id检索它?我一直在尝试改变这个主题:
var result = db.visitors.aggregate([
{$match: {"visits.building": "building02"}},
{$unwind: "$visits"},
{$project: {"visitorId": "$_id", "building": "$visits.building", "lastVisit": "$visits.lastVisit"}},
{$sort: {"lastVisit": 1}},
{$group: {"_id": "$building", "visitorId": {$last: "$visitorId"}, "lastVisit": {$last: "$lastVisit"}}},
{$match: {"_id": "building02"}},
{$limit: 1}
])
db.individuals.find({_id: {$eq: {result.visitorId: {$slice: [0, 1]}}}})
我宁愿在一个查询中完成整个操作,但是如果我做不到,那我就做不到。
您不需要$ group,因此无需担心$$ROOT
或努力找回所有字段。您将获得原始文档的副本(副本),而visits
数组中只剩下最近一次的访问。
> db.visitors.aggregate([
{ "$match" : { "visits.building" : "building02" } },
{ "$unwind" : "$visits" },
{ "$match" : { "visits.building" : "building02" } },
{ "$sort" : { "visits.lastVisit" : -1 } }, { "$limit" : 1 }
])
{
"_id" : ObjectId("5509e963b8b4702f49ffcee6"),
"visits" : {
"building" : "building02",
"lastVisit" : ISODate("2015-02-06T04:25:00Z")
},
"firstName" : "James",
"lastName" : "Smith",
"gender" : "male",
"accountNumber" : "123056780"
}
如果您需要整个visits
数组,那么我将_id
通过管道进行投影,并在管道返回后对其进行查找,以获取整个文档。
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我来说两句