嵌套过滤器:$ filter数组，然后是$ filter子数组 [英] Nested filters: $filter array, then $filter child array
问题描述
基本上，我正在尝试过滤出已删除"的OUT子文档和子子文档.这是我的架构的精简版:
Essentially I'm trying to filter OUT subdocuments and sub-subdocuments that have been "trashed". Here's a stripped-down version of my schema:
permitSchema = {
_id,
name,
...
feeClassifications: [
new Schema({
_id,
_trashed,
name,
fees: [
new Schema({
_id,
_trashed,
name,
amount
})
]
})
],
...
}
所以我可以通过feeClassifications获得想要的效果.但是我正在努力寻找一种对feeClassifications.fees也具有相同效果的方法.
So I'm able to get the effect I want with feeClassifications. But I'm struggling to find a way to have the same effect for feeClassifications.fees as well.
所以，这可以按需工作:
So, this works as desired:
Permit.aggregate([
{ $match: { _id: mongoose.Types.ObjectId(req.params.id) }},
{ $project: {
_id: 1,
_name: 1,
feeClassifications: {
$filter: {
input: '$feeClassifications',
as: 'item',
cond: { $not: {$gt: ['$$item._trashed', null] } }
}
}
}}
])
但是我也想过滤嵌套数组fees.我尝试了一些事情，包括:
But I also want to filter the nested array fees. I've tried a few things including:
Permit.aggregate([
{ $match: { _id: mongoose.Types.ObjectId(req.params.id) }},
{ $project: {
_id: 1,
_name: 1,
feeClassifications: {
$filter: {
input: '$feeClassifications',
as: 'item',
cond: { $not: {$gt: ['$$item._trashed', null] } }
},
fees: {
$filter: {
input: '$fees',
as: 'fee',
cond: { $not: {$gt: ['$$fee._trashed', null] } }
}
}
}
}}
])
似乎最接近 mongodb文档.但是我得到了错误:
this object is already an operator expression, and can't be used as a document expression (at 'fees')
Which seems to follow the mongodb docs the closest. But I get the error:
this object is already an operator expression, and can't be used as a document expression (at 'fees')
更新:-----------
Update: -----------
根据要求，以下是示例文档:
As requested, here's a sample document:
{
"_id" : ObjectId("57803fcd982971e403e3e879"),
"_updated" : ISODate("2016-07-11T19:24:27.204Z"),
"_created" : ISODate("2016-07-09T00:05:33.274Z"),
"name" : "Single Event",
"feeClassifications" : [
{
"_updated" : ISODate("2016-07-11T19:05:52.418Z"),
"_created" : ISODate("2016-07-11T17:49:12.247Z"),
"name" : "Event Type 1",
"_id" : ObjectId("5783dc18e09be99840fad29f"),
"fees" : [
{
"_updated" : ISODate("2016-07-11T18:51:10.259Z"),
"_created" : ISODate("2016-07-11T18:41:16.110Z"),
"name" : "Basic Fee",
"amount" : 156.5,
"_id" : ObjectId("5783e84cc46a883349bb2339")
},
{
"_updated" : ISODate("2016-07-11T19:05:52.419Z"),
"_created" : ISODate("2016-07-11T19:05:47.340Z"),
"name" : "Secondary Fee",
"amount" : 50,
"_id" : ObjectId("5783ee0bad7bf8774f6f9b5f"),
"_trashed" : ISODate("2016-07-11T19:05:52.410Z")
}
]
},
{
"_updated" : ISODate("2016-07-11T18:22:21.567Z"),
"_created" : ISODate("2016-07-11T18:22:21.567Z"),
"name" : "Event Type 2",
"_id" : ObjectId("5783e3dd540078de45bbbfaf"),
"_trashed" : ISODate("2016-07-11T19:24:27.203Z")
}
]
}
这是所需的输出(feeClassifications和fees都排除了已删除"子文档):
And here's the desired output ("trashed" subdocuments are excluded from BOTH feeClassifications AND fees):
{
"_id" : ObjectId("57803fcd982971e403e3e879"),
"_updated" : ISODate("2016-07-11T19:24:27.204Z"),
"_created" : ISODate("2016-07-09T00:05:33.274Z"),
"name" : "Single Event",
"feeClassifications" : [
{
"_updated" : ISODate("2016-07-11T19:05:52.418Z"),
"_created" : ISODate("2016-07-11T17:49:12.247Z"),
"name" : "Event Type 1",
"_id" : ObjectId("5783dc18e09be99840fad29f"),
"fees" : [
{
"_updated" : ISODate("2016-07-11T18:51:10.259Z"),
"_created" : ISODate("2016-07-11T18:41:16.110Z"),
"name" : "Basic Fee",
"amount" : 156.5,
"_id" : ObjectId("5783e84cc46a883349bb2339")
}
]
}
]
}
推荐答案
Since we want to filter both the outer and inner array fields, we can use the $map variable operator which return an array with the "values" we want.
在$map表达式中，我们提供了一个逻辑 $cond 等级 $filter 可以从两个文档和子文档数组字段.
In the $map expression, we provide a logical $conditional $filter to remove the non matching documents from both the document and subdocument array field.
条件为 $lt ，当字段子文档和/或子文档数组字段中没有"_trashed".
The conditions are $lt which return true when the field "_trashed" is absent in the sub-document and or in the sub-document array field.
请注意，在$cond表达式中，我们还为<false case>返回false.当然，我们需要对$map结果应用过滤器以删除所有false.
Note that in the $cond expression we also return false for the <false case>. Of course we need to apply filter to the $map result to remove all false.
Permit.aggregate(
[
{ "$match": { "_id": mongoose.Types.ObjectId(req.params.id) } },
{ "$project": {
"_updated": 1,
"_created": 1,
"name": 1,
"feeClassifications": {
"$filter": {
"input": {
"$map": {
"input": "$feeClassifications",
"as": "fclass",
"in": {
"$cond": [
{ "$lt": [ "$$fclass._trashed", 0 ] },
{
"_updated": "$$fclass._updated",
"_created": "$$fclass._created",
"name": "$$fclass.name",
"_id": "$$fclass._id",
"fees": {
"$filter": {
"input": "$$fclass.fees",
"as": "fees",
"cond": { "$lt": [ "$$fees._trashed", 0 ] }
}
}
},
false
]
}
}
},
"as": "cls",
"cond": "$$cls"
}
}
}}
]
)
在即将发布的MongoDB版本中(从撰写本文开始，以及从MongoDB 3.3.5开始)，您可以将$map表达式中的$cond表达式替换为$switch表达式:
In the upcoming MongoDB release (as of this writing and since MongoDB 3.3.5), You can replace the $cond expression in the the $map expression with a $switch expression:
Permit.aggregate(
[
{ "$match": { "_id": mongoose.Types.ObjectId(req.params.id) } },
{ "$project": {
"_updated": 1,
"_created": 1,
"name": 1,
"feeClassifications": {
"$filter": {
"input": {
"$map": {
"input": "$feeClassifications",
"as": "fclass",
"in": {
"$switch": {
"branches": [
{
"case": { "$lt": [ "$$fclass._trashed", 0 ] },
"then": {
"_updated": "$$fclass._updated",
"_created": "$$fclass._created",
"name": "$$fclass.name",
"_id": "$$fclass._id",
"fees": {
"$filter": {
"input": "$$fclass.fees",
"as": "fees",
"cond": { "$lt": [ "$$fees._trashed", 0 ] }
}
}
}
}
],
"default": false
}
}
}
},
"as": "cls",
"cond": "$$cls"
}
}
}}
]
)
这篇关于嵌套过滤器:$ filter数组，然后是$ filter子数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
