使用管道将数据从 msssql 流式传输到节点

Question

I am using node and node-mssql 6.0.1 and I use streams to get big amounts of data from the DB and send it to the front end.

I am trying to use pipe and stream as suggested by the docs , but I cannot get it to work.

My code is

const pool = new sql.ConnectionPool(config);
const poolConnect = pool.connect();

const testStream = (ws , id) => {     
    poolConnect.then((pool) => {   
      const request = new sql.Request(pool);
      request.pipe(stream);

         request
        .input('id_param', sql.Int, parseInt(id)) 
        .query('SELECT * FROM dataTable WHERE id = @id_param ')  
 }) 

I get stream is not defined .

My goal is to combine stream and pipe like the example here and then use websockets to send data to the client. I dont even know if it makes sense to combine stream and websockets. I cannot think of any way to combine or test

My current working code that uses just stream, looks like this

const sql = require('mssql');
const pool = new sql.ConnectionPool(config);
const poolConnect = pool.connect();

const testStream = (ws , id) => {       
    poolConnect.then((pool) => {   
      const request = new sql.Request(pool);
      request.stream = true;   
      request
      .input('id_param', sql.Int, parseInt(id))
      .query('SELECT * FROM table WHERE id = @id_param ')  

      let rowsToProcess = [];
      let data = [];  

      request.on('row', row => {   
        rowsToProcess.push(row); 
        if (rowsToProcess.length >= 20) {  
          request.pause();
          processRows(false);
        } 
      });

      request.on('done', () => {      
        processRows(true); 
        sql.close(); 
      });

      const processRows = () => { 
          rowsToProcess.forEach((item)=>{ 
                data.push(item.name);   
                data.push(item.surname);   
                data.push(item.age);   
            });    
          ws.send(JSON.stringify({ success:true, message: data }));
          rowsToProcess = [];
          data = []; 
      }//processRows 

    }) //poolConnect.then  

What am I missing here? Please help me get started with pipe and streams, I cannot find pipe/stream examples in Google

Thanks

Answer 1

Simple Writeable stream

const { Writable } = require('stream');

const stream = new Writable({
  write(chunk, encoding, callback) {
    console.log(chunk.toString());
    callback();    
  }
})