Hello
The first returns the value of the field “count” for index=1 in array2
{
_id: "some_id",
array1: [
{
_id: "level_1_id",
array2: [
{
_id: "level_2_id_0,
count: 0
},
{
_id: "level_2_id_1,
count: "tomatoes"
},
]
}
]
}
Would print
{"countValue" : "tomatoes"}
I thought this is what you want,if its not that,if you can give sample data,and the expected output.
For the second,if you want to update 1 element of an array and you know the index of that element you can do it in many ways,bellow are 3 of possible ways.
Data(collection with 1 document for example)
{myarray [1 2 3 4 5]}
All 3 results in (at index=3 we add 10)
{myarray [1 2 3 14 5]}
The 3 methods are
1)get the member of the index,update it,and concat array_before [updated_member] array_after
you need to be careful if those exists,here it only works for index in the middle
2)map after zipmap, [[1 0][2 1][3 2] [4 3] [5 4]] zipmap array with range(count(array))
the second is the index
3)reduce array to array,and keeping the index value ,update only in that index
First is simpler,but the other 2 can be used in many things.
Slice
[
{
"$addFields": {
"myarray": {
"$let": {
"vars": {
"m": {
"$arrayElemAt": [
"$myarray",
3
]
},
"array_before": {
"$slice": [
"$myarray",
3
]
},
"array_after": {
"$slice": [
"$myarray",
4,
{
"$size": "$myarray"
}
]
}
},
"in": {
"$let": {
"vars": {
"new_m": {
"$add": [
"$$m",
10
]
}
},
"in": {
"$concatArrays": [
"$$array_before",
[
"$$new_m"
],
"$$array_after"
]
}
}
}
}
}
}
}
]
Map on zip result with range
[
{
"$addFields": {
"myarray": {
"$map": {
"input": {
"$zip": {
"inputs": [
"$myarray",
{
"$range": [
0,
{
"$size": "$myarray"
}
]
}
]
}
},
"as": "m_index",
"in": {
"$let": {
"vars": {
"m": {
"$arrayElemAt": [
"$$m_index",
0
]
},
"index": {
"$arrayElemAt": [
"$$m_index",
1
]
}
},
"in": {
"$cond": [
{
"$eq": [
"$$index",
3
]
},
{
"$add": [
"$$m",
10
]
},
"$$m"
]
}
}
}
}
}
}
}
]
Reduce keeping the index value
[
{
"$addFields": {
"myarray": {
"$arrayElemAt": [
{
"$reduce": {
"input": "$myarray",
"initialValue": [
[],
0
],
"in": {
"$let": {
"vars": {
"arrray_index": "$$value",
"m": "$$this"
},
"in": {
"$let": {
"vars": {
"array": {
"$arrayElemAt": [
"$$arrray_index",
0
]
},
"index": {
"$arrayElemAt": [
"$$arrray_index",
1
]
}
},
"in": {
"$cond": [
{
"$eq": [
"$$index",
3
]
},
[
{
"$concatArrays": [
"$$array",
[
{
"$add": [
"$$m",
10
]
}
]
]
},
{
"$add": [
"$$index",
1
]
}
],
[
{
"$concatArrays": [
"$$array",
[
"$$m"
]
]
},
{
"$add": [
"$$index",
1
]
}
]
]
}
}
}
}
}
}
},
0
]
}
}
}
]
