Lazy-load modules from many entry point; reduced memory use

Author: dougwilson

Changes.md

@@ -7,6 +7,7 @@ you spot any mistakes.
 ## HEAD
 
 * Delay implied connect until after `.query` argument validation
+* Lazy-load modules from many entry point; reduced memory use
 
 ## v2.6.2 (2015-04-14)
 

index.js

@@ -1,26 +1,137 @@
-var Connection       = require('./lib/Connection');
-var ConnectionConfig = require('./lib/ConnectionConfig');
-var Types            = require('./lib/protocol/constants/types');
-var SqlString        = require('./lib/protocol/SqlString');
-var Pool             = require('./lib/Pool');
-var PoolConfig       = require('./lib/PoolConfig');
-var PoolCluster      = require('./lib/PoolCluster');
-
-exports.createConnection = function(config) {
+var Classes = Object.create(null);
+
+/**
+ * Create a new Connection instance.
+ * @param {object} config
+ * @public
+ */
+exports.createConnection = function createConnection(config) {
+  var Connection       = loadClass('Connection');
+  var ConnectionConfig = loadClass('ConnectionConfig');
+
   return new Connection({config: new ConnectionConfig(config)});
 };
 
-exports.createPool = function(config) {
+/**
+ * Create a new Pool instance.
+ * @param {object} config
+ * @public
+ */
+exports.createPool = function createPool(config) {
+  var Pool       = loadClass('Pool');
+  var PoolConfig = loadClass('PoolConfig');
+
   return new Pool({config: new PoolConfig(config)});
 };
 
-exports.createPoolCluster = function(config) {
+/**
+ * Create a new PoolCluster instance.
+ * @param {object} config
+ * @public
+ */
+exports.createPoolCluster = function createPoolCluster(config) {
+  var PoolCluster = loadClass('PoolCluster');
+
   return new PoolCluster(config);
 };
 
-exports.createQuery = Connection.createQuery;
+/**
+ * Create a new Query instance.
+ * @public
+ */
+exports.createQuery = function createQuery(sql, values, callback) {
+  var Connection = loadClass('Connection');
+
+  return Connection.createQuery(sql, values, callback);
+};
+
+/**
+ * Escape a value for SQL.
+ * @param {*} value
+ * @param {boolean} [stringifyObjects=false]
+ * @param {string} [timeZone=local]
+ * @public
+ */
+exports.escape = function escape(value, stringifyObjects, timeZone) {
+  var SqlString = loadClass('SqlString');
+
+  return SqlString.escape(value, stringifyObjects, timeZone);
+};
+
+/**
+ * Escape an identifier for SQL.
+ * @param {*} value
+ * @param {boolean} [forbidQualified]
+ * @public
+ */
+exports.escapeId = function escapeId(value, forbidQualified) {
+  var SqlString = loadClass('SqlString');
+
+  return SqlString.escapeId(value, forbidQualified);
+};
+
+/**
+ * Format SQL and replacement values into a SQL string.
+ * @param {string} sql
+ * @param {array} [values]
+ * @param {boolean} [stringifyObjects=false]
+ * @param {string} [timeZone=local]
+ * @public
+ */
+exports.format = function format(sql, values, stringifyObjects, timeZone) {
+  var SqlString = loadClass('SqlString');
+
+  return SqlString.format(sql, values, stringifyObjects, timeZone);
+};
+
+/**
+ * The type constants.
+ * @public
+ */
+Object.defineProperty(exports, 'Types', {
+  get: loadClass.bind(null, 'Types')
+});
+
+/**
+ * Load the given class.
+ * @private
+ */
+function loadClass(className) {
+  var Class = Classes[className];
+
+  if (Class !== undefined) {
+    return Class;
+  }
+
+  // This uses a switch for static require analysis
+  switch (className) {
+    case 'Connection':
+      Class = require('./lib/Connection');
+      break;
+    case 'ConnectionConfig':
+      Class = require('./lib/ConnectionConfig');
+      break;
+    case 'Pool':
+      Class = require('./lib/Pool');
+      break;
+    case 'PoolCluster':
+      Class = require('./lib/PoolCluster');
+      break;
+    case 'PoolConfig':
+      Class = require('./lib/PoolConfig');
+      break;
+    case 'SqlString':
+      Class = require('./lib/protocol/SqlString');
+      break;
+    case 'Types':
+      Class = require('./lib/protocol/constants/types');
+      break;
+    default:
+      throw new Error('Cannot find class \'' + className + '\'');
+  }
+
+  // Store to prevent invoking require()
+  Classes[className] = Class;
 
-exports.Types    = Types;
-exports.escape   = SqlString.escape;
-exports.escapeId = SqlString.escapeId;
-exports.format   = SqlString.format;
+  return Class;
+}