Aggregate.count

1. Interface Description

Function: Aggregation stage. Counts the number of input records and outputs a record with a specified field set to the count value. The count stage is equivalent to the operation of group + project.

declaration: count(string)

2. Input Parameters

Parameter	Type	Required	Description
-	expression	Required	string is the field name for the output record count. It cannot be an empty string, must not start with $, and must not contain the . character.

3. Response

Parameter	Type	Required	Description
-	Aggregate	Yes	Aggregation object

4. Sample Code

Suppose the collection items contains the following records:

{
  _id: "1",
  price: 10.5
}
{
  _id: "2",
  price: 50.3
}
{
  _id: "3",
  price: 20.8
}
{
  _id: "4",
  price: 80.2
}
{
  _id: "5",
  price: 200.3
}

Find the number of records where the price is greater than 50:

const tcb = require("@cloudbase/node-sdk");
const app = tcb.init({
  env: "xxx",
});

const db = app.database();
const $ = db.command.aggregate;
const _ = db.command;

exports.main = async (event, context) => {
  const res = await db
    .collection("items")
    .aggregate()
    .match({
      price: _.gt(50),
    })
    .count("expensiveCount")
    .end();
  console.log(res.data);
};

The returned result is as follows:

{
  "expensiveCount": 3
}