How to do search using elemMatch on array of SubDocument? I have document called ReportCollection with elements such as:-
如何在SubDocument数组上使用elemMatch进行搜索?我有一个名为ReportCollection的文档,其元素如下:
/* 0 */
{
"_id" : ObjectId("5507bfc435e9470c9aaaa2ac"),
"owner" : ObjectId("5507bfc31e14d78e177ceebd"),
"reports" : {
"xReport" : [
{
"name" : "xReport",
"parameters" : {
"x" : {
"dateTime" : "2015-03-11T18:30:00.000Z",
"unit" : 1,
"value" : 102
}
},
"createdBy" : ObjectId("5507bfc31e14d78e177ceebd"),
"modifiedBy" : ObjectId("5507bfc31e14d78e177ceebd"),
"_id" : ObjectId("5507bfc41e14d78e177ceebf")
}
]
}
}
I got reports.xReport[]._id as search parameter.
我将reports.xReport [] ._ id作为搜索参数。
My following attempt is failing :-
我的以下尝试失败了: -
db.reports.find ({ {owner: ObjectId("5507afd3d54bae3513c185cb")},
{ 'reports.xReport': {$elemMatch: {_id: ObjectId("5507afd3d54bae3513c185cd") }}} } )
1 个解决方案
#1
3
It seems like you are trying to put work into the "projection" that you should be doing in the query. Rather your statement should look more like this:
您似乎正在尝试将工作放入您应该在查询中执行的“投影”中。相反,你的陈述看起来应该更像这样:
db.reports.find(
{
"owner": ObjectId("5507bfc31e14d78e177ceebd"),
"reports.xReport._id": ObjectId("5507bfc41e14d78e177ceebf")
},
{ "reports.xReport.$": 1 }
)
So the "query" does the work of matching the array position and the "projection" just uses that position in the match.
因此“查询”执行匹配数组位置的工作,而“投影”只是在匹配中使用该位置。
Also note that you never really need $elemMatch
with a single field to match against. Only when multiple fields are required in the condition do you need to use this to match a specific "element".
另请注意,您永远不需要$ elemMatch与单个字段匹配。仅当条件中需要多个字段时,您才需要使用它来匹配特定的“元素”。
By the same token, that should also be in the "query" statement instead.
出于同样的原因,这也应该在“查询”语句中。
$elemMatch
in it's projected form cannot be used with sub-document fields through dotted notation.
其中$ elemMatch的投影形式不能与子文档字段一起使用,也可以通过虚线表示法使用。
#1
3
It seems like you are trying to put work into the "projection" that you should be doing in the query. Rather your statement should look more like this:
您似乎正在尝试将工作放入您应该在查询中执行的“投影”中。相反,你的陈述看起来应该更像这样:
db.reports.find(
{
"owner": ObjectId("5507bfc31e14d78e177ceebd"),
"reports.xReport._id": ObjectId("5507bfc41e14d78e177ceebf")
},
{ "reports.xReport.$": 1 }
)
So the "query" does the work of matching the array position and the "projection" just uses that position in the match.
因此“查询”执行匹配数组位置的工作,而“投影”只是在匹配中使用该位置。
Also note that you never really need $elemMatch
with a single field to match against. Only when multiple fields are required in the condition do you need to use this to match a specific "element".
另请注意,您永远不需要$ elemMatch与单个字段匹配。仅当条件中需要多个字段时,您才需要使用它来匹配特定的“元素”。
By the same token, that should also be in the "query" statement instead.
出于同样的原因,这也应该在“查询”语句中。
$elemMatch
in it's projected form cannot be used with sub-document fields through dotted notation.
其中$ elemMatch的投影形式不能与子文档字段一起使用,也可以通过虚线表示法使用。