I'm trying to make a query on MongoDB 3.4 where I add a field for one specific element of an array. Example of the object:
{
"_id": 1,
"people": [
{
"name": "Jhon Smith",
"age": "30",
"state": "NY"
},{
"name": "Clint Mercer",
"age": "50",
"state": "NY"
},{
"name": "Walter Smith",
"age": "40",
"state": "WI"
}
]
}
And I want to make a query where I'll add to this document an attribute with the first person with "Smith" in it's name. Example:
{
"_id": 1,
"people": [
{
"name": "Jhon Smith",
"age": "30",
"state": "NY"
},{
"name": "Clint Mercer",
"age": "50",
"state": "NY"
},{
"name": "Walter Smith",
"age": "40",
"state": "WI"
}
],
"firstSmith": {
"name": "Jhon Smith",
"age": "30",
"state": "NY"
}
}
I already have the _id of the document I want, but I can't understand how to make a query like this. I'm trying using aggregate with "$match" for the id and "$addFields" after, but I can't make a query that works for this field to find exactly what I want. I think it would be similar to the "findOne" query, but I can't find anything that works on "$addFields".
Obs: I DON'T want the "firstSmith" to be an array with just one "people" inside, I want it as is in the example.
I'd appreciate some help with this one.
$match - to filter the relevant document$filter with $regexMatch - to filter people array by the name propertyarrayElemAt - to get only the first element of above array$addFields - to add new field with value from above resultdb.collection.aggregate([
{
"$match": {
"_id": 1
}
},
{
"$addFields": {
"firstSmith": {
"$arrayElemAt": [
{
"$filter": {
"input": "$people",
"cond": {
"$regexMatch": {
"input": "$$this.name",
"regex": "Smith"
}
}
}
},
0
]
}
}
}
])