Node js + postgresql : Generate JSON with Node.js with multiple postgresql - json

Question

I have just started coding with node.js, I understand that node.js is asynchronous but not sure how to deal with this problem.
I'm querying postgresql and building a JSON as follows,
I added my code :
var express = require('express');
var router = express.Router();
var pg = require('pg');
var client = require('../routes/database.js');
var cookieParser = require('cookie-parser');
var dateFormat = require('date-format');
var async = require('async');
var today = dateFormat(new Date());
router.post('/conversation/my', function(req, res) {
var userId = 59;
var limit = 10;
var offset = 0;
var postgresql = "select id from conversation where party_id = '" + userId + "' and reply_id = 0 order by created_on desc limit " + limit + " offset " + offset + "";
var postsJSON = { };
var arr = new Array();
client.query(postgresql, function(err, data) {
if (err) {
console.log(err);
return rollback(client);
}
var rows = data.rows;
for ( i = 0; i < rows.length; i++) {
var post = rows[i];
var post_obj = {};
post_obj.id = post.id;
getConversationResponse(post.id, function(err, res) {
if (!err) {
post_obj.actor = res;
arr.push(post_obj);
console.log(JSON.stringify(arr));
res.send({
data : arr
});
}
});
}
});
});
function getConversationResponse(conversation_id, cb) {
client.query('SELECT * FROM people WHERE id ='+conversation_id+';', function(err, actor) {
client.query('SELECT * FROM users WHERE id ='+conversation_id+';', function(err, user) {
var actor_obj = {};
actor_obj.id = user.id;
actor_obj.name = user.name;
actor_obj.email = user.email;
client.end();
cb (null,actor_obj);
});
});
}
module.exports = router;
But i am getting error :
{ [Error: write EPIPE] code: 'EPIPE', errno: 'EPIPE', syscall: 'write' }
events.js:72
throw er; // Unhandled 'error' event
^
Error: write EPIPE
at errnoException (net.js:901:11)
at Object.afterWrite (net.js:718:19)
npm ERR! weird error 8
npm WARN This failure might be due to the use of legacy binary "node"
npm WARN For further explanations, please read
/usr/share/doc/nodejs/README.Debian

Answer 1

Your client.end(); should not be in the function. It should be after the first client.query for conversations has completed. Currently what happens is that for each conversation, you call the function to get the people/users, where you end the client. So the next conversation row cannot get the people/users.
Also, ideally you should join the three tables and get all the data in one shot.
var postgresql = "select id, people.*, users.* from conversation, people, users where party_id = '" + userId + "' and people.id=conversation.id and users.id=conversations.id and reply_id = 0 order by created_on desc limit " + limit + " offset " + offset + "";