Fixed generated sql for postgres substring function

lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php

@@ -57,10 +57,10 @@ class PostgreSqlPlatform extends AbstractPlatform
     public function getSubstringExpression($value, $from, $length = null)
     {
         if ($length === null) {
-            return 'SUBSTR(' . $value . ', ' . $from . ')';
+            return 'SUBSTRING(' . $value . ' FROM ' . $from . ')';
         }
 
-        return 'SUBSTR(' . $value . ', ' . $from . ', ' . $length . ')';
+        return 'SUBSTRING(' . $value . ' FROM ' . $from . ' FOR ' . $length . ')';
     }
 
     /**

tests/Doctrine/Tests/DBAL/Platforms/PostgreSqlPlatformTest.php

@@ -106,8 +106,8 @@ class PostgreSqlPlatformTest extends AbstractPlatformTestCase
         $this->assertEquals('SIMILAR TO', $this->_platform->getRegexpExpression(), 'Regular expression operator is not correct');
         $this->assertEquals('"', $this->_platform->getIdentifierQuoteCharacter(), 'Identifier quote character is not correct');
         $this->assertEquals('column1 || column2 || column3', $this->_platform->getConcatExpression('column1', 'column2', 'column3'), 'Concatenation expression is not correct');
-        $this->assertEquals('SUBSTR(column, 5)', $this->_platform->getSubstringExpression('column', 5), 'Substring expression without length is not correct');
-        $this->assertEquals('SUBSTR(column, 0, 5)', $this->_platform->getSubstringExpression('column', 0, 5), 'Substring expression with length is not correct');
+        $this->assertEquals('SUBSTRING(column FROM 5)', $this->_platform->getSubstringExpression('column', 5), 'Substring expression without length is not correct');
+        $this->assertEquals('SUBSTRING(column FROM 1 FOR 5)', $this->_platform->getSubstringExpression('column', 1, 5), 'Substring expression with length is not correct');
     }
 
     public function testGeneratesTransactionCommands()