Mongodb 返回多个子数组结果并排除其他返回结果 [英] Mongodb returning multiple sub array results and excluding other returned results
问题描述
我有以下带有节点数组的集合:
I have the following collection with a node array:
{
"_id" : ObjectId("55acf6187d4c31475417fa62"),
"node" : [
{
"-id" : "29331496",
"-uid" : "1899168",
"-changeset" : "26313303",
"-lat" : "-37.6104102",
"-lon" : "144.9459817",
"-timestamp" : "2014-10-25T03:36:51Z",
"-user" : "heyitsstevo",
"-visible" : "true",
"-version" : "6"
},
{
"-id" : "29331497",
"-uid" : "1899168",
"-version" : "2",
"-lon" : "144.9451088",
"-timestamp" : "2014-10-25T03:36:51Z",
"-user" : "heyitsstevo",
"-visible" : "true",
"-changeset" : "26313303",
"-lat" : "-37.601881"
},
{
"-id" : "29331498",
"-timestamp" : "2014-10-25T03:36:51Z",
"-version" : "3",
"-uid" : "1899168",
"-user" : "heyitsstevo",
"-visible" : "true",
"-changeset" : "26313303",
"-lat" : "-37.6011267",
"-lon" : "144.9448575"
},
{
"-lon" : "144.943302",
"-id" : "29331499",
"-timestamp" : "2011-11-23T03:21:40Z",
"-user" : "melb_guy",
"-version" : "9",
"-uid" : "11111",
"-visible" : "true",
"-changeset" : "9916439",
"-lat" : "-37.5983291"
},
{
"-id" : "60648717",
"-uid" : "46482",
"-user" : "Zulu99",
"-lat" : "-37.6796337",
"-lon" : "144.9220639",
"-timestamp" : "2009-12-12T21:29:36Z",
"-visible" : "true",
"-version" : "2",
"-changeset" : "3358816"
},
{
"-id" : "60648718",
"-timestamp" : "2009-12-12T21:29:35Z",
"-uid" : "46482",
"-version" : "2",
"-changeset" : "3358816",
"-user" : "Zulu99",
"-visible" : "true",
"-lat" : "-37.6787103",
"-lon" : "144.9224609"
},
{
"-id" : "60648719",
"-timestamp" : "2009-12-12T21:28:58Z",
"-user" : "Leon K",
"-version" : "2",
"-changeset" : "3358816",
"-uid" : "Zulu99",
"-visible" : "true",
"-lat" : "-37.677841",
"-lon" : "144.9227344"
}
]
}
如何返回所有具有-user"=Zulu99"的节点并排除其他任何节点?
How do I return all nodes that have the "-user" = "Zulu99" and exclude anything else?
我尝试了以下查询,但它只返回找到的第一个带有Zulu99"的节点:
I have tried the following query but it only returns the first node it finds with "Zulu99":
db.osm.find( { }, { node: {$elemMatch: {'-user': 'Zulu99'}}} )
推荐答案
如果您的文档大小大于 aggregation
$unwind
创建 笛卡尔积 问题,即每个数组对象都会创建多个文档,因此它会降低聚合查询速度,如果您想避免这种情况问题使用 $redact 如下所示:
If your documents size more then aggregation
$unwind
creates Cartesian Product problem i.e every array object creates multiple documents so it creates slow down aggregation query, If you want avoid this problem use $redact as like below :
db.collectionName.aggregate({
"$match": {
"node.-user": "Zulu99"
}
}, {
"$redact": {
"$cond": {
"if": {
"$eq": [{
"$ifNull": ["$-user", "Zulu99"]
}, "Zulu99"]
},
"then": "$$DESCEND",
"else": "$$PRUNE"
}
}
}).pretty()
<小时>
编辑
如果你想要多个条件,那么像这样使用 $cond
和 $and
If you want to multiple conditions then used $cond
with $and
like this
db.collectionName.aggregate({
"$match": {
"node.-user": "Zulu99",
"node.-lat": "-37.6787103"
}
}, {
"$redact": {
"$cond": {
"if": {
"$and": [{
"$eq": [{
"$ifNull": ["$-user", "Zulu99"]
}, "Zulu99"]
}, {
"$eq": [{
"$ifNull": ["$-lat", "-37.6787103"]
}, "-37.6787103"]
}]
},
"then": "$$DESCEND",
"else": "$$PRUNE"
}
}
}).pretty()
在上面的查询中,如果你想检查 -lat 和 -lon
lat 检查是否等于 -37.6787103
> 到 $gt 或 $lt
那么首先你应该改变你的文档中 lat 和 lon
的数据类型它看起来像 String
所以首先改变数据类型String to number
然后使用比较运算符.
In above query you get that lat
check whether is equal to -37.6787103
or not, if you want to check -lat and -lon
to $gt or $lt
then first you should changed your data type of both lat and lon
in your documents it looks like String
so first changed data type String to number
then used comparison operator.
第二件事,如果你只想匹配 node
数组对象然后在 readact
之后使用 group
像这样:
Second things if you want only matched node
array object then used group
after readact
like this :
db.collectionName.aggregate({
"$match": {
"node.-user": "Zulu99",
"node.-lat": "-37.6787103"
}
}, {
"$redact": {
"$cond": {
"if": {
"$and": [{
"$eq": [{
"$ifNull": ["$-user", "Zulu99"]
}, "Zulu99"]
}, {
"$eq": [{
"$ifNull": ["$-lat", "-37.6787103"]
}, "-37.6787103"]
}]
},
"then": "$$DESCEND",
"else": "$$PRUNE"
}
}
}, {
"$group": {
"_id": "$_id",
"node": {
"$first": "$node" // use $first
}
}
}).pretty()
新编辑
如果您想找出 gte 和 lte
条件,请遵循以下聚合:
If you want to find out gte and lte
condition then follow this aggregation :
db.collectionName.aggregate({
"$project": {
"check": {
"$setDifference": [{
"$map": {
"input": "$node",
"as": "node1",
"in": {
"$cond": {
"if": {
"$and": [{
"$and": [{
"$gte": ["$$node1.-lon", 100]
}, {
"$lte": ["$$node1.-lon", 150]
}]
}, {
"$and": [{
"$gte": ["$$node1.-lat", -50]
}, {
"$lte": ["$$node1.-lat", -10]
}]
}]
},
"then": "$$node1",
"else": false
}
}
}
},
[false]
]
}
}
}).pretty()
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