Implemented automatic identifier quoting for all drivers, this features

can be both controlled by configuration and using the Driver API. This
features is, nevertheless, very cpu expensive to have as a default, thus
it needs to be explicitly enabled.

Cake/Database/Dialect/PostgresDialectTrait.php

@@ -17,8 +17,6 @@
 namespace Cake\Database\Dialect;
 
 use Cake\Database\Expression\FunctionExpression;
-use Cake\Database\Expression\Comparison;
-use Cake\Database\Expression\OrderByExpression;
 use Cake\Database\Expression\UnaryExpression;
 use Cake\Database\Query;
 use Cake\Database\SqlDialectTrait;
@@ -29,7 +27,9 @@
  */
 trait PostgresDialectTrait {
 
-	use SqlDialectTrait;
+	use SqlDialectTrait {
+		_expressionTranslators as private _quotingTranslators;
+	}
 
 /**
  *  String used to start a database identifier quoting to make it safe
@@ -77,28 +77,11 @@ protected function _insertQueryTranslator($query) {
  */
 	protected function _expressionTranslators() {
 		$namespace = 'Cake\Database\Expression';
-		return [
-			$namespace . '\Comparison' => '_transformComparison',
-			$namespace . '\UnaryExpression' => '_transformUnary',
+		return $this->_quotingTranslators() + [
 			$namespace . '\FunctionExpression' => '_transformFunctionExpression'
 		];
 	}
 
-	protected function _transformComparison(Comparison $expression) {
-		$field = $expression->getField();
-		if (is_string($field)) {
-			$expression->field($this->quoteIdentifier($field));
-		}
-	}
-
-	protected function _transformUnary(UnaryExpression $expression) {
-		$expression->iterateParts(function($part) {
-			if (is_string($part)) {
-				return $this->quoteIdentifier($part);
-			}
-		});
-	}
-
 /**
  * Receives a FunctionExpression and changes it so that it conforms to this
  * SQL dialect.

Cake/Database/Dialect/SqliteDialectTrait.php

@@ -23,7 +23,9 @@
 
 trait SqliteDialectTrait {
 
-	use SqlDialectTrait;
+	use SqlDialectTrait {
+		_expressionTranslators as private _quotingTranslators;
+	}
 
 /**
  *  String used to start a database identifier quoting to make it safe
@@ -47,7 +49,7 @@ trait SqliteDialectTrait {
  */
 	protected function _expressionTranslators() {
 		$namespace = 'Cake\Database\Expression';
-		return [
+		return $this->_quotingTranslators() + [
 			$namespace . '\FunctionExpression' => '_transformFunctionExpression'
 		];
 	}

Cake/Database/Driver.php

@@ -38,6 +38,14 @@ abstract class Driver {
  */
 	protected $_baseConfig = [];
 
+/**
+ * Indicates whether or not the driver is doing automatic identifier quoting
+ * for all queries
+ *
+ * @var bool
+ */
+	protected $_autoQuoting = false;
+
 /**
  * Constructor
  *
@@ -47,6 +55,9 @@ abstract class Driver {
 	public function __construct($config = []) {
 		$config += $this->_baseConfig;
 		$this->_config = $config;
+		if (!empty($config['quoteIdentifiers'])) {
+			$this->autoQuoting(true);
+		}
 	}
 
 /**
@@ -180,6 +191,23 @@ public function isConnected() {
 		return $this->_connection !== null;
 	}
 
+/**
+ * Returns whether or not this driver should automatically quote identifiers
+ * in queries
+ *
+ * If called with a boolean argument, it will toggle the auto quoting setting
+ * to the passed value
+ *
+ * @param boolean $enable whether to enable auto quoting
+ * @return boolean
+ */
+	public function autoQuoting($enable = null) {
+		if ($enable === null) {
+			return $this->_autoQuoting;
+		}
+		return $this->_autoQuoting = (bool)$enable;
+	}
+
 /**
  * Destructor
  *

Cake/Database/Expression/FieldExpression.php

@@ -0,0 +1,58 @@
+<?php
+/**
+ * PHP Version 5.4
+ *
+ * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
+ * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ *
+ * Licensed under The MIT License
+ * For full copyright and license information, please see the LICENSE.txt
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ * @link          http://cakephp.org CakePHP(tm) Project
+ * @since         CakePHP(tm) v 3.0.0
+ * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
+ */
+namespace Cake\Database\Expression;
+
+use Cake\Database\ExpressionInterface;
+use Cake\Database\ValueBinder;
+
+class FieldExpression implements ExpressionInterface {
+
+	protected $_field;
+
+	public function __construct($field) {
+		$this->field($field);
+	}
+
+	public function field($field) {
+		$this->_field = $field;
+	}
+
+	public function getField() {
+		return $this->_field;
+	}
+
+/**
+ * Converts the expression to its string representation
+ *
+ * @param Cake\Database\ValueBinder $generator Placeholder generator object
+ * @return string
+ */
+	public function sql(ValueBinder $generator) {
+		return $this->_field;
+	}
+
+/**
+ * This method is a no-op, this is a leaf type of expression,
+ * hence there is nothing to traverse
+ *
+ * @param callable $visitor
+ * @return void
+ */
+	public function traverse(callable $callable) {
+	}
+
+}

Cake/Database/Expression/OrderByExpression.php

@@ -49,8 +49,18 @@ public function sql(ValueBinder $generator) {
 		return sprintf('ORDER BY %s', implode(', ', $order));
 	}
 
-	protected function _addConditions(array $conditions, array $types) {
-		$this->_conditions = array_merge($this->_conditions, $conditions);
+/**
+ * Auxiliary function used for decomposing a nested array of conditions and build
+ * a tree structure inside this object to represent the full SQL expression.
+ *
+ * New order by expressions are merged to existing ones
+ *
+ * @param array $orders list of order by expressions
+ * @param array $types list of types associated on fields referenced in $conditions
+ * @return void
+ */
+	protected function _addConditions(array $orders, array $types) {
+		$this->_conditions = array_merge($this->_conditions, $orders);
 	}
 
 }

Cake/Database/Expression/QueryExpression.php

@@ -341,7 +341,7 @@ public function sql(ValueBinder $generator) {
  */
 	public function traverse(callable $callable) {
 		foreach ($this->_conditions as $c) {
-			if ($c instanceof self) {
+			if ($c instanceof ExpressionInterface) {
 				$callable($c);
 				$c->traverse($callable);
 			}
@@ -354,15 +354,21 @@ public function traverse(callable $callable) {
  * which the currently visited part will be replaced. If the callable function
  * returns null then the part will be discarded completely from this expression
  *
+ * The callback function will receive each of the conditions as first param and
+ * the key as second param. It is possible to declare the second parameter as
+ * passed by reference, this will enable you to change the key under which the
+ * modified part is stored.
+ *
  * @param callable $callable
  * @return QueryExpression
  */
 	public function iterateParts(callable $callable) {
 		$parts = [];
 		foreach ($this->_conditions as $k => $c) {
-			$part = $callable($c);
+			$key =& $k;
+			$part = $callable($c, $key);
 			if ($part !== null) {
-				$parts[] = $part;
+				$parts[$key] = $part;
 			}
 		}
 		$this->_conditions = $parts;