Lru cache

documentation/Prepared-Statements.md

@@ -32,3 +32,7 @@ connection.prepare('select ? + ? as tests', function(err, statement) {
 });
 ```
 Note that you should not use statement after connection reset (`changeUser()` or disconnect). Statement scope is connection, you need to prepare statement for each new connection in order to use it.
+
+# Configuration
+
+`maxPreparedStatements` : We keep the cached statements in a [lru-cache](https://github.com/isaacs/node-lru-cache). Default size is `16000` but you can use this option to override it. Any statements that are dropped from cache will be `closed`.

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: this.config.maxPreparedStatements,
+    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 {

lib/connection_config.js

@@ -70,6 +70,7 @@ function ConnectionConfig (options) {
                                                  options.flags || '');
 
   this.connectAttributes = options.connectAttributes;
+  this.maxPreparedStatements = options.maxPreparedStatements || 16000;
 }
 
 ConnectionConfig.mergeFlags = function (default_flags, user_flags) {

package.json

@@ -37,6 +37,7 @@
     "double-ended-queue": "2.1.0-0",
     "iconv-lite": "^0.4.13",
     "long": "^3.2.0",
+    "lru-cache": "^4.0.1",
     "named-placeholders": "1.1.1",
     "object-assign": "^4.1.0",
     "readable-stream": "2.1.5",

test/integration/connection/test-execute-cached.js

@@ -24,9 +24,9 @@ connection.execute(q, [123], function (err, _rows, _fields) {
         throw err;
       }
       rows2 = _rows;
-      assert(Object.keys(connection._statements).length == 1);
-      assert(connection._statements[key].query == q);
-      assert(connection._statements[key].parameters.length == 1);
+      assert(connection._statements.length == 1);
+      assert(connection._statements.get(key).query == q);
+      assert(connection._statements.get(key).parameters.length == 1);
       connection.end();
     });
   });
@@ -38,4 +38,3 @@ process.on('exit', function () {
   assert.deepEqual(rows1, [{'test': 125}]);
   assert.deepEqual(rows2, [{'test': 126}]);
 });
-