我正在编写聚合以获取带有本地集合的外部集合数据。
db.getCollection('orders').aggregate([
{
$match: {
status: "UNASSIGNED",
serviceLocationId: "83177"
}
}, {
$lookup: {
from: "servicelocations",
localField: "serviceLocationId",
foreignField: "serviceLocationId",
as: "locations"
}
}, {
$unwind: "$locations"
}])
我得到了：
{
"_id" : ObjectId("59d32b5c360198e441b67545"),
"accountId" : 1.0,
"orderId" : "AQ137O1701240",
"serviceLocationId" : "83177",
"orderDate" : "2017-09-18T18:29:00.000Z",
"description" : "AQ137O1701240",
"serviceType" : "Delivery",
"orderSource" : "Import",
"takenBy" : "KARIM",
"plannedDeliveryDate" : ISODate("2017-10-09T00:00:00.000Z"),
"plannedDeliveryTime" : "",
"actualDeliveryDate" : "",
"actualDeliveryTime" : "",
"deliveredBy" : "",
"size1" : 25.0,
"size2" : 464.0,
"size3" : 46.0,
"jobPriority" : 1.0,
"cancelReason" : "",
"cancelDate" : "",
"cancelBy" : "",
"reasonCode" : "",
"reasonText" : "",
"status" : "UNASSIGNED",
"lineItems" : [
{
"ItemId" : "MMGW001",
"size1" : 25.0,
"size2" : 464.38,
"size3" : 46.875
}
],
"locations" : {
"_id" : ObjectId("59ce18e172dbf6926093e189"),
"accountId" : 1.0,
"serviceLocationId" : "83177",
"regionId" : "1",
"zoneId" : "DXBZONE1",
"description" : "EXPRESS BLUE MART SUPERMARKET",
"locationPriority" : 1.0,
"accountTypeId" : 1.0,
"locationType" : "SERVICELOCATION",
"location" : {
"makani" : "",
"lng" : 55.179042,
"lat" : 25.098741
},
"deliveryDays" : "MTWRFSU",
"serviceTimeTypeId" : "1",
"timeWindow" : {
"timeWindowTypeId" : "1"
},
"address1" : "",
"address2" : "",
"phone" : "",
"city" : "",
"county" : "",
"state" : "",
"country" : "",
"zipcode" : "",
"imageUrl" : "",
"contact" : {
"name" : "",
"email" : ""
},
"status" : "ACTIVE",
"createdBy" : "",
"updatedBy" : "",
"updateDate" : ""
}
}
但我需要：
{
"_id" : ObjectId("59d32b5c360198e441b67545"),
"accountId" : 1.0,
"orderId" : "AQ137O1701240",
"serviceLocationId" : "83177",
"orderDate" : "2017-09-18T18:29:00.000Z",
"description" : "AQ137O1701240",
"serviceType" : "Delivery",
"orderSource" : "Import",
"takenBy" : "KARIM",
"plannedDeliveryDate" : ISODate("2017-10-09T00:00:00.000Z"),
"plannedDeliveryTime" : "",
"actualDeliveryDate" : "",
"actualDeliveryTime" : "",
"deliveredBy" : "",
"size1" : 25.0,
"size2" : 464.0,
"size3" : 46.0,
"jobPriority" : 1.0,
"cancelReason" : "",
"cancelDate" : "",
"cancelBy" : "",
"reasonCode" : "",
"reasonText" : "",
"status" : "UNASSIGNED",
"lineItems" : [
{
"ItemId" : "MMGW001",
"size1" : 25.0,
"size2" : 464.38,
"size3" : 46.875
}
],
"locations" : {
"lng" : 55.179042,
"lat" : 25.098741
}
}
答案 0 :(得分：2)
基本上，使用$project作为最后阶段，然后选择所需的所有特定字段。不幸的是$addFields已经出局了，因为它实际上会将子键与现有子键合并。所以看似简单：
{ "$addFields": {
"locations": {
"lng": "$locations.location.lng",
"lat": "$locations.location.lat"
}
}}
只提供"locations"下的所有现有内容以及新定义的密钥。当然，除非您$unwind之后直接$lookup，否则如果这不会导致BSON limit to be exceeded，您可以这样做。 （这称为$lookup + $unwind合并）
然后我们可以将$addFields与$map一起使用，因为我们可以简单地“重新映射”数组：
{ "$addFields": {
"locations": {
"$map": {
"input": "$locations",
"as": "l",
"in": {
"lng": "$$l.location.lng",
"lat": "$$l.location.lat"
}
}
}
}},
{ "$unwind": "$locations" }
然后$unwind如果您仍然需要在重新映射之后。
所以$project就是：
{ "$project": {
"accountId" : 1,
"orderId" : 1,
"serviceLocationId" : 1,
"orderDate" : 1,
"description" : 1,
"serviceType" : 1,
"orderSource" : 1,
"takenBy" : 1,
"plannedDeliveryDate" : 1,
"plannedDeliveryTime" : 1,
"actualDeliveryDate" : 1,
"actualDeliveryTime" : 1,
"deliveredBy" : 1,
"size1" : 1,
"size2" : 1,
"size3" : 1,
"jobPriority" : 1,
"cancelReason" : 1,
"cancelDate" : 1,
"cancelBy" : 1,
"reasonCode" : 1,
"reasonText" : 1,
"status" : 1,
"lineItems" : 1,
"locations" : {
"lng": "$locations.location.lng",
"lat": "$locations.location.lat"
}
}}
简单而又啰嗦。
如果您拥有$objectToArray和$arrayToObject的MongoDB 3.4.4或更高版本，那么您可能会更喜欢它：
{ "$replaceRoot": {
"newRoot": {
"$arrayToObject": {
"$concatArrays": [
{ "$filter": {
"input": { "$objectToArray": "$$ROOT" },
"cond": { "$ne": [ "$$this.k", "locations" ] }
}},
{ "$objectToArray": {
"locations": {
"lng": "$locations.location.lng",
"lat": "$locations.location.lat"
}
}}
]
}
}
}}
基本上从$$ROOT获取整个文档中的所有字段，将其转换为数组格式。然后，我们通过“密钥名称”$filter "location"字段，使用新的"location"密钥$concatArrays将其再次转换为数组。
最后当然$arrayToObject接受并转换回一个对象，该对象作为最终输出提供给$replaceRoot newRoot。
因此，在$addFields $unwind之后使用$lookup之外的其中任何一个都会为您提供正确的结果：
/* 1 */
{
"_id" : ObjectId("59d32b5c360198e441b67545"),
"accountId" : 1.0,
"orderId" : "AQ137O1701240",
"serviceLocationId" : "83177",
"orderDate" : "2017-09-18T18:29:00.000Z",
"description" : "AQ137O1701240",
"serviceType" : "Delivery",
"orderSource" : "Import",
"takenBy" : "KARIM",
"plannedDeliveryDate" : ISODate("2017-10-09T00:00:00.000Z"),
"plannedDeliveryTime" : "",
"actualDeliveryDate" : "",
"actualDeliveryTime" : "",
"deliveredBy" : "",
"size1" : 25.0,
"size2" : 464.0,
"size3" : 46.0,
"jobPriority" : 1.0,
"cancelReason" : "",
"cancelDate" : "",
"cancelBy" : "",
"reasonCode" : "",
"reasonText" : "",
"status" : "UNASSIGNED",
"lineItems" : [
{
"ItemId" : "MMGW001",
"size1" : 25.0,
"size2" : 464.38,
"size3" : 46.875
}
],
"locations" : {
"lng" : 55.179042,
"lat" : 25.098741
}
}
作为一个预览，$expr对MongoDB 3.6进行了更具表现力的改造。所以你实际上可以明确地说明字段返回：
{ "$lookup": {
"from": "servicelocations",
"let": { "serviceLocationId": "$serviceLocationId" },
"pipeline": [
{ "$match": { "$expr": { "$eq": [ "serviceLocationId", "$$serviceLocationId" ] } }},
{ "$project": {
"_id": 0,
"lng": "$location.lng",
"lat": "$location.lat"
}}
],
"as": "locations"
}}
实际发布时更方便一点。这实际上使用$match而不是localField和foreignField来定义子管道的$project阶段中的“加入”条件。然后，您只需$lookup要返回的字段，然后进入{{3}}定位的数组。
展望未来，这是您想要采取的一般方法，因为它限制了实际返回的内容。