Compare integers stored as Strings in Mongodb - mongodb

Question

In the below collection, column "qty" holds the integer values but the datatype is string.
I want to compare the "qty" field with an integer in the aggregate and "warehouse" field with a string "A". ("qty" > 2 and "warehouse" = "A")
[Can't change the datatype in the collection to integer as huge dependency is present]
Edit : Need to retrieve all the columns and all the documents matching the criteria.
Query : getting improper results
db.runCommand(
{
aggregate: "products", pipeline: [
{
$match: {
instock: {
$elemMatch: {
warehouse: "A",
qty: { $gt: "2" }
}
}
}
},
{ $project: { _id: 0 } }],
cursor: { batchSize: 200 }
});
Result : not getting documents where item = journal though it satisfies the conditions
/* 1 */
{
"item" : "paper",
"instock" : [
{
"warehouse" : "A",
"qty" : "60"
},
{
"warehouse" : "B",
"qty" : "15"
}
]
},
/* 2 */
{
"item" : "planner",
"instock" : [
{
"warehouse" : "A",
"qty" : "22"
},
{
"warehouse" : "B",
"qty" : "5"
}
]
}
Products Collection
[
{
"item": "journal",
"instock": [
{
"warehouse": "A",
"qty": "11"
},
{
"warehouse": "C",
"qty": "15"
}
]
},
{
"item": "paper",
"instock": [
{
"warehouse": "A",
"qty": "60"
},
{
"warehouse": "B",
"qty": "15"
}
]
},
{
"item": "planner",
"instock": [
{
"warehouse": "A",
"qty": "22"
},
{
"warehouse": "B",
"qty": "5"
}
]
}
]
Getting improper results as greater than operator in this case is working lexicographically but it should work like integers. Though I tried converting that to double but I am getting no results.
Query with $convert to double : no result
db.runCommand(
{
aggregate: "products", pipeline: [
//{ $match: { "item": { $in: ["planner", "paper","journal"] } } },
{
$match: {
instock: {
$elemMatch: {
warehouse: "A",
qty: {
$gt: [
{$convert:{ input: "$qty", to: "double" }}, 5]
}
}
}
}
},
{ $project: { _id: 0 } }],
cursor: { batchSize: 200 }
});

Answer 1

Try this:
db.products.aggregate([
{
$unwind: "$instock"
},
{
$match: {
$expr: {
$and: [
{
$eq: [
"$instock.warehouse",
"A"
]
},
{
$gt: [
{
$toInt: "$instock.qty"
},
2
]
}
]
}
}
},
{
$group: {
_id: "$_id",
item: {
$first: "$item"
},
instock: {
$push: "$instock"
}
}
},
{
$project: {
_id: 0
}
}
])
MongoPlayground

Answer 2

Try this, it uses $filter to retain objects has criteria :
db.runCommand(
{
aggregate: "products", pipeline: [
{ $match: { 'instock.warehouse': 'A' } },
{
$addFields: {
instockCheck: {
$filter: {
input: '$instock', as: 'each', cond: {
$and: [{ $gt: [{ $toInt: '$$each.qty' }, 2] },
{ $eq: ['$$each.warehouse', 'A'] }]
}
}
}
}
}, { $match: { instockCheck: { $gt: [] } } }, { $project: { instockCheck: 0, _id: 0 } }],
cursor: { batchSize: 200 }
});
Test : MongoDB-Playground