node.js - MongoDB unknown top level operator: $expr nodejs

Question

I tried finding solution for this online, but no success.

This is the code:

Invoice.count( { $expr: {$gt: [ "$totalAmount", "$remainingDebt" ]} } ).exec(callback);

where totalAmount and remainingDebt are fields in schema Invoice.

The result I get is: "unknown top level operator $expr".

I am using mongoose 5.0.11 and mongo lab.

Any ideas?

Answer 1

由于 MLab 提供了 Mongo 的最大 3.6 版本，因此您将哪个版本用于 MongoDB，因此您需要修改 Query 或升级 Mongo DB 版本。

Answer 2

我正在使用这个查询。

InvoiceModel.aggregate([
    {
      $expr:{'$gt': [ "$totalAmount", "$remainingDebt" ]}
    },
    {
      $count:'COUNT'
    }
 ],(error, result)=>{
   console.log(result)
})