MDL-21874 - ddl object names cache. Don't use cache keys anymore. Leads to conflicts.

lib/ddl/sql_generator.php

@@ -949,6 +949,9 @@ abstract class sql_generator {
 
     /// Implement one basic cache to avoid object name duplication
     /// along all the request life, but never to return cached results
+    /// We need this because sql statements are created before executing
+    /// them, hence names doesn't exist "phisically" yet in DB, so we need
+    /// to known which ones have been used
         if (!isset($used_names)) {
             static $used_names = array();
         }
@@ -1001,7 +1004,7 @@ abstract class sql_generator {
         }
 
     /// Add the name to the cache
-        $used_names[$tablename.'-'.$fields.'-'.$suffix] = $namewithsuffix;
+        $used_names[] = $namewithsuffix;
 
     /// Quote it if necessary (reserved words)
         $namewithsuffix = $this->getEncQuoted($namewithsuffix);