added lru cache for statements

Author: sushantdhiman

lib/commands/change_user.js

@@ -37,7 +37,7 @@ ChangeUser.prototype.start = function (packet, connection) {
   this.currentConfig.database = this.database;
   this.currentConfig.charsetNumber = this.charsetNumber;
   // reset prepared statements cache as all statements become invalid after changeUser
-  connection._statements = {};
+  connection._statements.reset();
   connection.writePacket(packet.toPacket());
   return ChangeUser.prototype.handshakeResult;
 };

lib/connection.js

@@ -4,8 +4,8 @@ var Tls = require('tls');
 var Timers = require('timers');
 var EventEmitter = require('events').EventEmitter;
 var Queue = require('double-ended-queue');
-
 var SqlString = require('sqlstring');
+var LRU = require('lru-cache');
 
 var PacketParser = require('./packet_parser.js');
 var Packet = require('./packets/packet.js');
@@ -51,7 +51,10 @@ function Connection (opts)
   this._paused = false;
   this._paused_packets = new Queue();
 
-  this._statements = {};
+  this._statements = LRU({
+    max: 1000,
+    dispose: function (key, statement) { statement.close(); }
+  });
 
   // TODO: make it lru cache
   // https://github.com/mercadolibre/node-simple-lru-cache
@@ -498,9 +501,9 @@ Connection.prototype.unprepare = function unprepare (sql) {
     options.sql = sql;
   }
   var key = statementKey(options);
-  var stmt = this._statements[key];
+  var stmt = this._statements.get(key);
   if (stmt) {
-    this._statements[key] = null;
+    this._statements.del(key);
     stmt.close();
   }
   return stmt;
@@ -531,7 +534,7 @@ Connection.prototype.execute = function execute (sql, values, cb) {
 
   var connection = this;
   var key = statementKey(options);
-  var statement = connection._statements[key];
+  var statement = connection._statements.get(key);
 
   options.statement = statement;
   var executeCommand = new Commands.Execute(options, cb);
@@ -547,7 +550,7 @@ Connection.prototype.execute = function execute (sql, values, cb) {
         return;
       }
       executeCommand.statement = stmt;
-      connection._statements[key] = stmt;
+      connection._statements.set(key, stmt);
       connection.addCommand(executeCommand);
     });
   } else {