Add update with join support for Postgres.

Postgres requires some query fudging to make joins with updates
syntactically valid. Add a query translator that moves joins around and
creates a 'from' clause.

lib/Cake/Database/Dialect/PostgresDialectTrait.php

@@ -80,6 +80,42 @@ protected function _selectQueryTranslator($query) {
 		return $query;
 	}
 
+/**
+ * Returns an update query that has been transformed for Postgres.
+ *
+ * Postgres requires joins to be defined in the FROM list instead of
+ * as standard joins. This translator will erase joins and replace them with
+ * an expression object in the FROM clause.
+ *
+ * @param Cake\Database\Query $query
+ * @return Cake\Database\Query
+ */
+	protected function _updateQueryTranslator($query) {
+		$joins = $query->clause('join');
+		if ($joins) {
+			$sql = '';
+			foreach ($joins as $i => $join) {
+				if ($i == 0) {
+					$sql .= sprintf('%s %s', $join['table'], $join['alias']);
+					if (isset($join['conditions']) && count($join['conditions'])) {
+						$query->where($join['conditions']);
+					}
+					continue;
+				}
+				$sql .= sprintf(' %s JOIN %s %s', $join['type'], $join['table'], $join['alias']);
+				if (isset($join['conditions']) && count($join['conditions'])) {
+					$sql .= sprintf(' ON %s', $join['conditions']);
+				} else {
+					$sql .= ' ON 1 = 1';
+				}
+			}
+			$expr = $query->newExpr()->add($sql);
+			$query->join([], [], true);
+			$query->from([$expr]);
+		}
+		return $query;
+	}
+
 /**
  * Returns a function that will be used as a callback for a results decorator.
  * this function is responsible for deleting the artificial column in results

lib/Cake/Database/Query.php

@@ -291,7 +291,7 @@ protected function _traverseDelete(callable $visitor) {
  * @return void
  */
 	protected function _traverseUpdate(callable $visitor) {
-		$parts = ['update', 'join', 'set', 'where'];
+		$parts = ['update', 'join', 'set', 'from', 'where'];
 		foreach ($parts as $name) {
 			call_user_func($visitor, $this->_parts[$name], $name);
 		}
@@ -597,7 +597,6 @@ public function join($tables = null, $types = [], $overwrite = false) {
 			if (!($t['conditions']) instanceof ExpressionInterface) {
 				$t['conditions'] = $this->newExpr()->add($t['conditions'], $types);
 			}
-
 			$joins[] = $t + ['type' => 'INNER', 'alias' => is_string($alias) ? $alias : null];
 		}
 
@@ -623,6 +622,11 @@ public function join($tables = null, $types = [], $overwrite = false) {
 	protected function _buildJoinPart($parts) {
 		$joins = '';
 		foreach ($parts as $join) {
+			if ($join instanceof ExpressionInterface) {
+				$joins .= $join->sql();
+				continue;
+			}
+
 			$joins .= sprintf(' %s JOIN %s %s', $join['type'], $join['table'], $join['alias']);
 			if (isset($join['conditions']) && count($join['conditions'])) {
 				$joins .= sprintf(' ON %s', $join['conditions']);

lib/Cake/Test/TestCase/Database/Driver/PostgresTest.php

@@ -20,6 +20,7 @@
 use Cake\Core\Configure;
 use Cake\Database\Connection;
 use Cake\Database\Driver\Postgres;
+use Cake\Database\Query;
 use \PDO;
 
 /**
@@ -135,4 +136,28 @@ public function testConnectionConfigCustom() {
 		$driver->connect();
 	}
 
+	public function testUpdateWithJoin() {
+		$driver = $this->getMock('Cake\Database\driver\Postgres', ['_connect', 'connection']);
+		$connection = new Connection(Configure::read('Datasource.test'));
+		$connection->driver($driver);
+
+		$query = new Query($connection);
+
+		$query->update('articles')
+			->set('title', 'New title')
+			->join([
+				'table' => 'authors',
+				'alias' => 'a',
+				'conditions' => 'author_id = a.id'
+			])
+			->join('comments')
+			->where(['articles.id' => 1]);
+		$result = $query->sql(true);
+
+		$this->assertContains('UPDATE articles SET title = :', $result);
+		$this->assertContains('FROM authors a INNER JOIN comments  ON 1 = 1', $result);
+		$this->assertContains('WHERE (articles.id = :', $result);
+		$this->assertContains('AND author_id = a.id)', $result);
+	}
+
 }