我有以下收藏集
位置信息收集
print(a)
我们是否抛出任何查询并使用上述数据获取位置的直接节点。
示例。 我说印度应该返回
[1, 2, 3, 4, 5, 6, 7, 8]
谢谢
答案 0 :(得分:0)
使用Aggregation framework,我们可以获得预期的结果。
以下查询为我们提供了结果,在此查询中,我使用了$lookup,$match,$project
db.location.aggregate([
{
$lookup: {
from: "location",
localField: "location",
foreignField: "parentLocation",
as:"Result"
}
},
{$match:{ "Result": {$exists:true, $ne:[]}, parentLocation: {$ne: null} }},
{$project :{ parentLocation:1, location:1, "Result.location":1}},
{$match: {location: "Maharashstra"}}
])
收藏夹中的文档
{ "_id" : ObjectId("5b83e4860c35ef57411a575b"), "id" : 1, "name" : "l1", "location" : "pune", "parentLocation" : "Maharashstra" }
{ "_id" : ObjectId("5b83e4860c35ef57411a575c"), "id" : 2, "name" : "l2", "location" : "nashik", "parentLocation" : "Maharashstra" }
{ "_id" : ObjectId("5b83e4860c35ef57411a575d"), "id" : 3, "name" : "l3", "location" : "mumbai", "parentLocation" : "Maharashstra" }
{ "_id" : ObjectId("5b83e4860c35ef57411a575e"), "id" : 4, "name" : "l4", "location" : "Maharashstra", "parentLocation" : "India" }
{ "_id" : ObjectId("5b83e4860c35ef57411a575f"), "id" : 5, "name" : "l5", "location" : "India", "parentLocation" : null }
{ "_id" : ObjectId("5b83fec90c35ef57411a5760"), "id" : 6, "name" : "l6", "location" : "Chennai", "parentLocation" : "Tamilnadu" }
{ "_id" : ObjectId("5b83fec90c35ef57411a5761"), "id" : 7, "name" : "l7", "location" : "Trichy", "parentLocation" : "Tamilnadu" }
{ "_id" : ObjectId("5b83fec90c35ef57411a5762"), "id" : 8, "name" : "l8", "location" : "Alapuzha", "parentLocation" : "Kerala" }
{ "_id" : ObjectId("5b83fec90c35ef57411a5763"), "id" : 9, "name" : "l9", "location" : "Kerala", "parentLocation" : "India" }
{ "_id" : ObjectId("5b83fec90c35ef57411a5764"), "id" : 10, "name" : "l10", "location" : "Tamilnadu", "parentLocation" : "India" }
执行上述查询后,结果为
{
"_id" : ObjectId("5b83e4860c35ef57411a575e"),
"location" : "Maharashstra",
"parentLocation" : "India",
"Result" : [
{
"location" : "pune"
},
{
"location" : "nashik"
},
{
"location" : "mumbai"
}
]
}
如果我们减少查询中的最后一个$ match,那么它将返回完整的状态分组。
db.location.aggregate([
{
$lookup: {
from: "location",
localField: "location",
foreignField: "parentLocation",
as:"Result"
}
},
{$match:{ "Result": {$exists:true, $ne:[]}, parentLocation: {$ne: null} }},
{$project :{ parentLocation:1, location:1, "Result.location":1}}
])
上述查询的结果是
{
"_id" : ObjectId("5b83e4860c35ef57411a575e"),
"location" : "Maharashstra",
"parentLocation" : "India",
"Result" : [
{
"location" : "pune"
},
{
"location" : "nashik"
},
{
"location" : "mumbai"
}
]
}
{
"_id" : ObjectId("5b83fec90c35ef57411a5763"),
"location" : "Kerala",
"parentLocation" : "India",
"Result" : [
{
"location" : "Alapuzha"
}
]
}
{
"_id" : ObjectId("5b83fec90c35ef57411a5764"),
"location" : "Tamilnadu",
"parentLocation" : "India",
"Result" : [
{
"location" : "Chennai"
},
{
"location" : "Trichy"
}
]
}