404 error in Node.js when doing app.get with postgres as Db

var express = require('express');
var router = express.Router();

var db = require('../queries');

router.get('/api/preference', function(req,res){ res.send('hi'); })


module.exports = router;

var promise = require('bluebird');

var options ={
    //Initialization options
    promiseLib : promise
};

var pgp = require('pg-promise')(options);
var db = pgp({
    host: 'localhost',
    port: 5432,
    database: 'pmc',
    user: 'tarun',
    password: 'pes'
});
var connectionstring = 'postgres://tarun:pes@localhost:5432/pmc';
var db = pgp(connectionstring);


//add query funtions

module.exports = {
    getAllPreference : getAllPreference
};


function getAllPreference(req,res,next){
    db.any('select * from core.preferences')
      .then(function(data){
        res.status(200)
           .json({
               status : 'success',
               data : data,
               message: 'Retrieved ALL preferences'
           });
      })
      .catch(function (err) {
        return next(err);
      });
}

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');

var index = require('./routes/index');
var users = require('./routes/users');

var app = express();



// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', index);
app.use('/users', users);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

module.exports = app;