Mongodb query select embedded document - mongodb

Question

I have following Mongodb document. Would like to fetch document where participant = 'xxx' and (message.touserid = 'xxx' or message.fromuserid = 'xxx').
I am using following query but it is returning all messages instead of just one. Could you please let me know how to achieve this result?
{ "$and" : [ { "participants" : { "$regex" : "56d314a8e4b04d7f98cfd0c6"} , "$or" : [ { "messages.touserId" : "56d314a8e4b04d7f98cfd0c6"} , { "messages.formuserId" : "56d314a8e4b04d7f98cfd0c6"}]}]} fields: { "_id" : "0" , "product" : "0" , "participants" : "0" , "messages" : "0"}
{
"_id": {
"$oid": "574eb878027520c2158268d6"
},
"_class": "com.idearealty.product.shopchat.persistence.model.Discussion",
"participants": "56d314a8e4b04d7f98cfd0c6,56d5d48ee4b0cc330f512a47,56d9d599e4b0cc330f512aaa,57130299e4b08c554c1092c7,56841002eceefce22f455c7f",
"messages": [
{
"_id": {
"$oid": "574eb874027520c2158268d2"
},
"formuserId": "56841002eceefce22f455c7f",
"fromuser": "9674642375",
"touserId": "56d314a8e4b04d7f98cfd0c6",
"touser": "debopam_r",
"message": "Creating Discussion",
"isMute": false,
"index": 1,
"createDate": {
"$date": "2016-06-01T10:27:00.500Z"
},
"lastModifiedDate": {
"$date": "2016-06-01T10:27:00.501Z"
},
"createdBy": "9674642375",
"lastModifiedBy": "9674642375"
},
{
"_id": {
"$oid": "574eb875027520c2158268d3"
},
"formuserId": "56841002eceefce22f455c7f",
"fromuser": "9674642375",
"touserId": "56d5d48ee4b0cc330f512a47",
"touser": "Raushan",
"message": "Creating Discussion",
"isMute": false,
"index": 2,
"createDate": {
"$date": "2016-06-01T10:27:01.295Z"
},
"lastModifiedDate": {
"$date": "2016-06-01T10:27:01.295Z"
},
"createdBy": "9674642375",
"lastModifiedBy": "9674642375"
},
{
"_id": {
"$oid": "574eb875027520c2158268d4"
},
"formuserId": "56841002eceefce22f455c7f",
"fromuser": "9674642375",
"touserId": "56d9d599e4b0cc330f512aaa",
"touser": "anirbanshop1",
"message": "Creating Discussion",
"isMute": false,
"index": 3,
"createDate": {
"$date": "2016-06-01T10:27:01.962Z"
},
"lastModifiedDate": {
"$date": "2016-06-01T10:27:01.962Z"
},
"createdBy": "9674642375",
"lastModifiedBy": "9674642375"
},
{
"_id": {
"$oid": "574eb876027520c2158268d5"
},
"formuserId": "56841002eceefce22f455c7f",
"fromuser": "9674642375",
"touserId": "57130299e4b08c554c1092c7",
"touser": "dummyshop",
"message": "Creating Discussion",
"isMute": false,
"index": 4,
"createDate": {
"$date": "2016-06-01T10:27:02.574Z"
},
"lastModifiedDate": {
"$date": "2016-06-01T10:27:02.574Z"
},
"createdBy": "9674642375",
"lastModifiedBy": "9674642375"
}
],
"messageCount": 4,
"createDate": {
"$date": "2016-06-01T10:27:04.041Z"
},
"lastModifiedDate": {
"$date": "2016-06-01T10:27:04.041Z"
},
"createdBy": "9674642375",
"lastModifiedBy": "9674642375"
}

Answer 1

As this is a complex match on elements - $elemMatch cannot be used in this case,
so aggregation framework is a helper.
var match = {
$match : {
participants : /56d314a8e4b04d7f98cfd0c6/
}
}
var unwind = {
$unwind : "$messages"
}
var matchSecond = {
$match : {
$or : [{
"messages.touserId" : "56d314a8e4b04d7f98cfd0c6"
}, {
"messages.formuserId" : "56d314a8e4b04d7f98cfd0c6"
}
]
}
}
var projection = {
$project : {
_id : 0,
messages : 1
}
}
db.deb.aggregate([match, unwind, matchSecond, projection])
and output:
{
"messages" : {
"_id" : {
"oid" : "574eb874027520c2158268d2"
},
"formuserId" : "56841002eceefce22f455c7f",
"fromuser" : "9674642375",
"touserId" : "56d314a8e4b04d7f98cfd0c6",
"touser" : "debopam_r",
"message" : "Creating Discussion",
"isMute" : false,
"index" : 1.0,
"createDate" : {
"date" : "2016-06-01T10:27:00.500Z"
},
"lastModifiedDate" : {
"date" : "2016-06-01T10:27:00.501Z"
},
"createdBy" : "9674642375",
"lastModifiedBy" : "9674642375"
}
}