How to multi update of a nested array in MondoDB? - mongodb

Question

I have documents in a MongoDB 'playground' collection following the below "schema" :
{
"_id": ObjectId("54423b40c92f9fffb486a6d4"),
"ProjectFileId": 1,
"SourceLanguageId": 2,
"TargetSegments": [
{
"LanguageId": 1,
"Segment": "Something",
"Colors": [
1,
2,
3
],
"Heights": [
1,
2,
3
],
"Widths": [
1,
2,
3
]
},
{
"LanguageId": 1,
"Segment": "Something",
"Colors": [
1,
2,
3
],
"Heights": [
1,
2,
3
],
"Widths": [
1,
2,
3
]
}
]
}
And the following update query:
db.playground.update({
$and: [
{
"TargetSegments.Colors": {
$exists: true
}
},
{
"ProjectFileId": 1
},
{
"SourceLanguageId": 2
},
{
"TargetSegments": {
$elemMatch: {
"LanguageId": 1
}
}
}
]
},
{
$set: {
"TargetSegments.$.Segment": null,
"TargetSegments.$.Colors": [],
"TargetSegments.$.Widths": [],
"TargetSegments.$.Heights": []
}
},
false, true)
After the execution of the query the result is:
{
"_id": ObjectId("54423b40c92f9fffb486a6d4"),
"ProjectFileId": 1,
"SourceLanguageId": 2,
"TargetSegments": [
{
"LanguageId": 1,
"Segment": null,
"Colors": [],
"Heights": [],
"Widths": []
},
{
"LanguageId": 1,
"Segment": "Something",
"Colors": [
1,
2,
3
],
"Heights": [
1,
2,
3
],
"Widths": [
1,
2,
3
]
}
]
}
As you can see, only the first element of the "TargetSegments" array is updated.
How can I update all the elements of the TargetSegments array in one update query?

Answer 1

Its because you are using $ operator: The positional $ operator identifies an element (not multi) in an array to update without explicitly specifying the position of the element in the array. To project, or return, an array element from a read operation, see the $ projection operator.
You can use below code to do it:
db.playground.find({
$and: [
{
"TargetSegments.Colors": {
$exists: true
}
},
{
"ProjectFileId": 1
},
{
"SourceLanguageId": 2
},
{
"TargetSegments": {
$elemMatch: {
"LanguageId": 1
}
}
}
]
}).forEach(function(item)
{
var targets = item.TargetSegments;
for(var index = 0; index < targets.length; index++)
{
var target = targets[index];
target.Segment = null,
target.Colors= [],
target.Widths= [],
target.Heights= []
}
db.playground.save(item);
});