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
我有一个带有节点数组的以下集合:
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"且不包含其他内容的节点?
How do I return all nodes that have the "-user" = "Zulu99" and exclude anything else?
我尝试了以下查询,但是它只返回它找到的带有"Zulu99"的第一个节点:
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
如果文档尺寸更大,则aggregation
$unwind
创建 $ redact 如下:
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()
编辑
如果要同时满足多个条件,则可以将$cond
与$and
一起使用
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,您得到lat
检查是否等于-37.6787103
,如果要检查-lat and -lon
至$gt or $lt
,则首先应在您的计算机中更改两个lat and lon
的数据类型.文档看起来像String
,因此首先更改数据类型String to number
,然后使用
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 $lt
then first you should changed your data type of both lat and lon
in your documents it looks like String
so first changed data type String to number
then used comparison operator.
第二件事,如果只想匹配node
数组对象,则在readact
之后使用group
,像这样:
Second things if you want only matched node
array object then used group
after readact
like this :
db.collectionName.aggregate({
"$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 $first
}
}
}).pretty()
新编辑
如果要查找gte and lte
条件,请遵循以下聚合:
If you want to find out gte and lte
condition then follow this aggregation :
db.collectionName.aggregate({
"$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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