UnExpected output from mongoDB - node.js

Question

I am using mongoose to connect and query mongoDB.
Now if I have the following code:
return new Promise((resolve) => {
mongoose.connection.db.collection('offer').aggregate([{
$match: {
$or: [
{
ccChecked: {
$lt: new Date(currentDay + 'T00:00:00.000Z')
}
},
{
ccChecked: {
$exists: 0
}
}
],
_id: { $in: offerObjIds }
}
},
{ $sample: { size: 2 } }
], (err, res) => {
console.log('res is', res);
resolve(res);
});
});
The result provided is fine and we get the expected output.
But if we have the following query, and I provide SAMPLE_SIZE as 2:
const sampleSize = process.env.SAMPLE_SIZE
return new Promise((resolve) => {
mongoose.connection.db.collection('offer').aggregate([{
$match: {
$or: [
{
ccChecked: {
$lt: new Date(currentDay + 'T00:00:00.000Z')
}
},
{
ccChecked: {
$exists: 0
}
}
],
_id: { $in: offerObjIds }
}
},
{ $sample: { size: sampleSize } }
], (err, res) => {
console.log('res is', res);
resolve(res);
});
});
In this case, I get the result as undefined. Can someone provide explanation why such behaviour and how to resolve this through process.env variable.

Answer 1

Verify that sampleSize is an integer. It could be string coming from process.env variables.
{ $sample: { size: <positive integer> } }
Update:
I tested out a script on my command line. See the results:
set SAMPLE_SIZE=1&& node example.js
example.js
console.log(process.env);
Output:
{ ... SAMPLE_SIZE: '1', ... }