allow removing column comment on some platforms

lib/Doctrine/DBAL/Platforms/OraclePlatform.php

@@ -571,9 +571,21 @@ LEFT JOIN user_cons_columns r_cols
             }
 
             $column = $columnDiff->column;
-            $fields[] = $column->getQuotedName($this). ' ' . $this->getColumnDeclarationSQL('', $column->toArray());
-            if ($columnDiff->hasChanged('comment') && $comment = $this->getColumnComment($column)) {
-                $commentsSQL[] = $this->getCommentOnColumnSQL($diff->name, $column->getName(), $comment);
+            $columnHasChangedComment = $columnDiff->hasChanged('comment');
+
+            /**
+             * Do not add query part if only comment has changed
+             */
+            if ( ! ($columnHasChangedComment && count($columnDiff->changedProperties) === 1)) {
+                $fields[] = $column->getQuotedName($this). ' ' . $this->getColumnDeclarationSQL('', $column->toArray());
+            }
+
+            if ($columnHasChangedComment) {
+                $commentsSQL[] = $this->getCommentOnColumnSQL(
+                    $diff->name,
+                    $column->getName(),
+                    $this->getColumnComment($column)
+                );
             }
         }
 

lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php

@@ -432,8 +432,12 @@ class PostgreSqlPlatform extends AbstractPlatform
                 }
             }
 
-            if ($columnDiff->hasChanged('comment') && $comment = $this->getColumnComment($column)) {
-                $commentsSQL[] = $this->getCommentOnColumnSQL($diff->name, $column->getName(), $comment);
+            if ($columnDiff->hasChanged('comment')) {
+                $commentsSQL[] = $this->getCommentOnColumnSQL(
+                    $diff->name,
+                    $column->getName(),
+                    $this->getColumnComment($column)
+                );
             }
 
             if ($columnDiff->hasChanged('length')) {
@@ -463,6 +467,16 @@ class PostgreSqlPlatform extends AbstractPlatform
         return array_merge($sql, $tableSql, $columnSql);
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getCommentOnColumnSQL($tableName, $columnName, $comment)
+    {
+        $comment = $comment === null ? 'NULL' : "'$comment'";
+
+        return "COMMENT ON COLUMN $tableName.$columnName IS $comment";
+    }
+
     /**
      * {@inheritDoc}
      */

tests/Doctrine/Tests/DBAL/Functional/Schema/SchemaManagerFunctionalTestCase.php

@@ -535,6 +535,20 @@ class SchemaManagerFunctionalTestCase extends \Doctrine\Tests\DbalFunctionalTest
         $columns = $this->_sm->listTableColumns("column_comment_test");
         $this->assertEquals(1, count($columns));
         $this->assertEquals('This is a comment', $columns['id']->getComment());
+
+        $tableDiff = new \Doctrine\DBAL\Schema\TableDiff('column_comment_test');
+        $tableDiff->changedColumns['id'] = new \Doctrine\DBAL\Schema\ColumnDiff(
+            'id', new \Doctrine\DBAL\Schema\Column(
+                'id', \Doctrine\DBAL\Types\Type::getType('integer'), array('primary' => true)
+            ),
+            array('comment')
+        );
+
+        $this->_sm->alterTable($tableDiff);
+
+        $columns = $this->_sm->listTableColumns("column_comment_test");
+        $this->assertEquals(1, count($columns));
+        $this->assertEmpty($columns['id']->getComment());
     }
 
     /**

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

@@ -374,6 +374,12 @@ abstract class AbstractPlatformTestCase extends \Doctrine\Tests\DbalTestCase
     {
         $tableDiff = new TableDiff('mytable');
         $tableDiff->addedColumns['quota'] = new \Doctrine\DBAL\Schema\Column('quota', \Doctrine\DBAL\Types\Type::getType('integer'), array('comment' => 'A comment'));
+        $tableDiff->changedColumns['foo'] = new \Doctrine\DBAL\Schema\ColumnDiff(
+            'foo', new \Doctrine\DBAL\Schema\Column(
+                'foo', \Doctrine\DBAL\Types\Type::getType('string')
+            ),
+            array('comment')
+        );
         $tableDiff->changedColumns['bar'] = new \Doctrine\DBAL\Schema\ColumnDiff(
             'bar', new \Doctrine\DBAL\Schema\Column(
                 'baz', \Doctrine\DBAL\Types\Type::getType('string'), array('comment' => 'B comment')

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

@@ -203,7 +203,7 @@ class MySqlPlatformTest extends AbstractPlatformTestCase
 
     public function getAlterTableColumnCommentsSQL()
     {
-        return array("ALTER TABLE mytable ADD quota INT NOT NULL COMMENT 'A comment', CHANGE bar baz VARCHAR(255) NOT NULL COMMENT 'B comment'");
+        return array("ALTER TABLE mytable ADD quota INT NOT NULL COMMENT 'A comment', CHANGE foo foo VARCHAR(255) NOT NULL, CHANGE bar baz VARCHAR(255) NOT NULL COMMENT 'B comment'");
     }
 
     public function getCreateTableColumnTypeCommentsSQL()

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

@@ -268,8 +268,8 @@ class OraclePlatformTest extends AbstractPlatformTestCase
     {
         return array(
             "ALTER TABLE mytable ADD (quota NUMBER(10) NOT NULL)",
-            "ALTER TABLE mytable MODIFY (baz  VARCHAR2(255) NOT NULL)",
             "COMMENT ON COLUMN mytable.quota IS 'A comment'",
+            "COMMENT ON COLUMN mytable.foo IS ''",
             "COMMENT ON COLUMN mytable.baz IS 'B comment'",
         );
     }

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

@@ -254,6 +254,7 @@ class PostgreSqlPlatformTest extends AbstractPlatformTestCase
         return array(
             "ALTER TABLE mytable ADD quota INT NOT NULL",
             "COMMENT ON COLUMN mytable.quota IS 'A comment'",
+            "COMMENT ON COLUMN mytable.foo IS NULL",
             "COMMENT ON COLUMN mytable.baz IS 'B comment'",
         );
     }