odataserver/src/mssql.js

OData server with support for BLOBs

// mssql.js
//---------
//
// 2014-11-25, Jonas Colmsjö
//------------------------------
//
// RDBMS Backend for MS SQL Server. This is _work in progress_, only sqlRead
// has been implemented so far.
//
//
// Using
// [Google JavaScript Style Guide](http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml)
//


var self_ = this;

var util = require('util');
var h = require('./helpers.js');

var mssql = require('../win/node_modules/mssql');
var u = require('underscore');

h.debug = true;

// helper for running SQL queries. `resultFunc` determines what should happen
// with the result
var runQuery = function(config, sql, resultFunc, endFunc) {
  var self = this;

  // Connect to db and run callback
  var conn = mssql.connect(config, function(err) {
    h.log.debug('MSSQL runQuery sql (' + JSON.stringify(config) + '): ' +
      sql);

    if (err) {
      h.log.log('MSSQL error' + err);
      return;
    }

    var request = new mssql.Request();
    request.stream = true;

    // or request.execute(procedure);
    request.query(sql);

    request.on('recordset', function(columns) {
      // Emitted once for each recordset in a query
      h.log.debug('MSSQL Recordset columns: ' + columns);
    });

    request.on('row', function(row) {
      resultFunc(row);
      h.log.debug('MSSQL runQuery result: ' + JSON.stringify(row));
    });

    request.on('error', function(err) {
      // May be emitted multiple times
      h.log.log('MSSQL error:' + err);
    });

    request.on('done', function(returnValue) {
      h.log.debug('MSSQL runQuery end.');
      conn.close();
      if (endFunc !== undefined) {
        endFunc();
      }
    });

  });

};

var mssqlBase = function(credentials) {
  var self = this;

  // You can use 'server: localhost\\instance' to connect to named instance
  // You can enable streaming globally
  self.config = {
    user: credentials.user,
    password: credentials.password,
    server: credentials.host,
    database: credentials.database,
    options: global.CONFIG.MSSQL.OPTIONS
  };

  self.sql = null;

};

// Write results into a stream
mssqlBase.prototype.pipe = function(writeStream) {
  var self = this;
  runQuery(self.config, self.sql,
    function(row) {
      writeStream.write(JSON.stringify(row));
    }
  );
};

// Close the MSSQL connection
mssqlBase.prototype.end = function() {
  var self = this;
  self.connection.end();
};

//
// Mssql readable object
// ---------------------
//
// This is NOT a stream but there is a function for piping the result
// into a stream. There is also a function for fetching all rows into
// a array.

// private helper function
var processRow = function(row) {
  var self = this;

  if (self.processRowFunc !== undefined) {
    return self.processRowFunc(row);
  }
  return row;
};

// * sql - the sql select statement to run
// * processRowFunc - each row can be manipulated with this function before
// it is returned
exports.mssqlRead = function(credentials, sql, processRowFunc) {
  var self = this;

  mssqlBase.call(this, credentials);

  self.sql = sql;
  self.processRowFunc = processRowFunc;
  self.result = [];

};

// inherit mssqlBase prototype
exports.mssqlRead.prototype = Object.create(mssqlBase.prototype);

// Fetch all rows in to an array. `done` is then called with this
// array is its only argument
exports.mssqlRead.prototype.fetchAll = function(done) {
  var self = this;

  runQuery(self.connection, self.sql,
    function(row) {
      self.result.push(processRow(row));
    },
    function() {
      self.connection.end();
      done(self.result);
    }
  );

};