2 files changed, 32 insertions, 3 deletions
diff --git a/phpBB/includes/db/migration/migration.php b/phpBB/includes/db/migration/migration.php
index 4271751362..cf1e97b3b1 100644
--- a/phpBB/includes/db/migration/migration.php
+++ b/phpBB/includes/db/migration/migration.php
@@ -84,6 +84,21 @@ abstract class phpbb_db_migration
 	}
 
 	/**
+	* Allows you to check if the migration is effectively installed (entirely optionall)
+	*
+	* This is checked when a migration is installed. If true is returned, the migration will be set as
+	* installed without performing the database changes.
+	* This function is intended to help moving to migrations from a previous database updater, where some
+	* migrations may have been installed already even though they are not yet listed in the migrations table.
+	*
+	* @return bool True if this migration is installed, False if this migration is not installed (checked on install)
+	*/
+	public function effectively_installed()
+	{
+		return false;
+	}
+
+	/**
 	* Updates the database schema by providing a set of change instructions
 	*
 	* @return array Array of schema changes (compatible with db_tools->perform_schema_changes())
diff --git a/phpBB/includes/db/migrator.php b/phpBB/includes/db/migrator.php
index 6b249e3ee0..b56da95b1a 100644
--- a/phpBB/includes/db/migrator.php
+++ b/phpBB/includes/db/migrator.php
@@ -271,10 +271,24 @@ class phpbb_db_migrator
 			'class'	=> $migration,
 		);
 
-		if (!isset($this->migration_state[$name]))
+		if ($migration->effectively_installed())
 		{
-			$state['migration_start_time'] = time();
-			$this->insert_migration($name, $state);
+			$state = array(
+				'migration_depends_on'	=> $migration->depends_on(),
+				'migration_schema_done' => true,
+				'migration_data_done'	=> true,
+				'migration_data_state'	=> '',
+				'migration_start_time'	=> 0,
+				'migration_end_time'	=> 0,
+			);
+		}
+		else
+		{
+			if (!isset($this->migration_state[$name]))
+			{
+				$state['migration_start_time'] = time();
+				$this->insert_migration($name, $state);
+			}
 		}
 
 		if (!$state['migration_schema_done'])