Let's say I have a Lesson schema and it contains an array of question subdocuments.
How would I get those lessons where it is marked as completed but all the questions in the array have isDeleted: true
I thought of something like
Lesson.find({ isComplete: true, 'questions.isDeleted': true })
but that gets the lessons if at least one of the questions is deleted. How would I assert the condition for all of the questions?
Santiago Trujillo
You can't use the dot notation as it flattens the array, What you can do is use $expr, this allows the use of aggregation operators, like $reduce.
Now we can iterate over the array and see if all the documents satisfy the conditions, like so:
db.collection.find({
isComplete: true,
$expr: {
$eq: [
{
$reduce: {
input: "$questions",
initialValue: 0,
in: {
$sum: [
"$$value",
{
$cond: [
{
$ne: [
"$$this.isDeleted",
true
]
},
1,
0
]
}
]
}
}
},
0
]
}
})