diff --git a/aiida/backends/djsite/db/management/__init__.py b/aiida/backends/djsite/db/management/__init__.py
index 9cc4e5e7c4..5941c2e482 100644
--- a/aiida/backends/djsite/db/management/__init__.py
+++ b/aiida/backends/djsite/db/management/__init__.py
@@ -7,788 +7,4 @@
 # For further information on the license, see the LICENSE.txt file        #
 # For further information please visit http://www.aiida.net               #
 ###########################################################################
-from django.contrib.auth import models as auth_models
-from django.conf import settings
-
-# ====================================
-#   SqLite Transive Closure
-#====================================
-
-
-
-def get_sqlite_tc_create_purgelist(links_table_name,
-                                   links_table_input_field,
-                                   links_table_output_field,
-                                   closure_table_name,
-                                   closure_table_parent_field,
-                                   closure_table_child_field):
-    return """
-CREATE TABLE purge_list (Id int);
-"""
-
-
-def get_sqlite_tc_create_trigger_update(links_table_name,
-                                        links_table_input_field,
-                                        links_table_output_field,
-                                        closure_table_name,
-                                        closure_table_parent_field,
-                                        closure_table_child_field):
-    from string import Template
-
-    trigger_update_text = Template("""
-CREATE TRIGGER update_tc INSERT ON $links_table_name
-WHEN 
-NOT EXISTS (
-      SELECT Id FROM $closure_table_name 
-      WHERE $closure_table_parent_field = new.$links_table_input_field
-         AND $closure_table_child_field = new.$links_table_output_field
-         AND depth = 0
-         ) 
-AND NOT new.$links_table_input_field = new.$links_table_output_field
-AND NOT EXISTS (
-      SELECT id FROM $closure_table_name 
-        WHERE $closure_table_parent_field = new.$links_table_output_field 
-        AND $closure_table_child_field = new.$links_table_input_field
-        )
-
-BEGIN
-
-INSERT INTO $closure_table_name (
-         $closure_table_parent_field,
-         $closure_table_child_field,
-         depth)
-      VALUES (
-         new.$links_table_input_field,
-         new.$links_table_output_field,
-         0);
-
-    UPDATE $closure_table_name
-      SET entry_edge_id = (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0)
-        , exit_edge_id = (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0)
-        , direct_edge_id = (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0) 
-      WHERE id = (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0);
-
-    INSERT INTO $closure_table_name (
-      entry_edge_id,
-      direct_edge_id,
-      exit_edge_id,
-      $closure_table_parent_field,
-      $closure_table_child_field,
-      depth) 
-      SELECT id
-         , (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0)
-         , (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0)
-         , $closure_table_parent_field 
-         , new.$links_table_output_field
-         , depth + 1
-        FROM $closure_table_name
-        WHERE $closure_table_child_field = new.$links_table_input_field;
-
-    INSERT INTO $closure_table_name (
-      entry_edge_id,
-      direct_edge_id,
-      exit_edge_id,
-      $closure_table_parent_field,
-      $closure_table_child_field,
-      depth)
-      SELECT (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0)
-        , (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0)
-        , id 
-        , new.$links_table_input_field
-        , $closure_table_child_field
-        , depth + 1
-        FROM $closure_table_name
-        WHERE $closure_table_parent_field = new.$links_table_output_field;
-
-    INSERT INTO $closure_table_name (
-      entry_edge_id,
-      direct_edge_id,
-      exit_edge_id,
-      $closure_table_parent_field,
-      $closure_table_child_field,
-      depth)
-      SELECT A.id
-        , (SELECT id from $closure_table_name where $closure_table_parent_field=new.$links_table_input_field and $closure_table_child_field=new.$links_table_output_field and depth=0)
-        , B.id
-        , A.$closure_table_parent_field
-        , B.$closure_table_child_field
-        , A.depth + B.depth + 2
-     FROM $closure_table_name A
-        CROSS JOIN $closure_table_name B
-     WHERE A.$closure_table_child_field = new.$links_table_input_field
-       AND B.$closure_table_parent_field = new.$links_table_output_field;
-
-END;
-""")
-    return trigger_update_text.substitute(links_table_name=links_table_name,
-                                          links_table_input_field=links_table_input_field,
-                                          links_table_output_field=links_table_output_field,
-                                          closure_table_name=closure_table_name,
-                                          closure_table_parent_field=closure_table_parent_field,
-                                          closure_table_child_field=closure_table_child_field)
-
-
-def get_sqlite_tc_create_trigger_delete(links_table_name,
-                                        links_table_input_field,
-                                        links_table_output_field,
-                                        closure_table_name,
-                                        closure_table_parent_field,
-                                        closure_table_child_field):
-    from string import Template
-
-    trigger_delete = Template("""
-CREATE TRIGGER deleted_from DELETE ON $links_table_name
-WHEN 
-EXISTS( 
-  SELECT id FROM $closure_table_name
-  WHERE $closure_table_parent_field = old.$links_table_input_field
-  AND $closure_table_child_field = old.$links_table_output_field 
-  AND depth = 0 )
-BEGIN
-
-INSERT INTO purge_list
-      SELECT id FROM $closure_table_name
-      WHERE $closure_table_parent_field = old.$links_table_input_field
-      AND $closure_table_child_field = old.$links_table_output_field 
-      AND depth = 0;
-
-INSERT INTO purge_list
-    SELECT id FROM $closure_table_name
-    WHERE depth > 0
-    AND ( entry_edge_id IN ( SELECT Id FROM purge_list ) 
-    OR direct_edge_id IN ( SELECT Id FROM purge_list )
-    OR exit_edge_id IN ( SELECT Id FROM purge_list ) )
-    AND Id NOT IN (SELECT Id FROM purge_list );
-
-DELETE FROM $closure_table_name WHERE Id IN ( SELECT Id FROM purge_list);
-
-DELETE FROM purge_list;
-
-END
-
-""")
-    return trigger_delete.substitute(links_table_name=links_table_name,
-                                     links_table_input_field=links_table_input_field,
-                                     links_table_output_field=links_table_output_field,
-                                     closure_table_name=closure_table_name,
-                                     closure_table_parent_field=closure_table_parent_field,
-                                     closure_table_child_field=closure_table_child_field)
-
-
-def get_sqlite_tc_create_trigger_delete_NEW(links_table_name,
-                                            links_table_input_field,
-                                            links_table_output_field,
-                                            closure_table_name,
-                                            closure_table_parent_field,
-                                            closure_table_child_field):
-    from string import Template
-
-    trigger_delete_NEW = Template("""
-CREATE TRIGGER deleted_from DELETE ON $links_table_name
-BEGIN
-
-DELETE FROM $closure_table_name WHERE Id IN (
-      SELECT id FROM $closure_table_name
-      WHERE $closure_table_parent_field = old.$links_table_input_field
-      AND $closure_table_child_field = old.$links_table_output_field
-      AND depth = 0);
-
-END
-""")
-    return trigger_delete_NEW.substitute(links_table_name=links_table_name,
-                                         links_table_input_field=links_table_input_field,
-                                         links_table_output_field=links_table_output_field,
-                                         closure_table_name=closure_table_name,
-                                         closure_table_parent_field=closure_table_parent_field,
-                                         closure_table_child_field=closure_table_child_field)
-
-
-def get_sqlite_tc_create_trigger_loop_NEW(links_table_name,
-                                          links_table_input_field,
-                                          links_table_output_field,
-                                          closure_table_name,
-                                          closure_table_parent_field,
-                                          closure_table_child_field):
-    from string import Template
-
-    trigger_loop_NEW = Template("""
-CREATE TRIGGER path_delete_recursive DELETE ON $closure_table_name 
-WHEN 
-EXISTS( 
-      SELECT id FROM $closure_table_name
-    WHERE (entry_edge_id = old.id 
-    OR direct_edge_id = old.id
-    OR exit_edge_id = old.id)
-    AND (id <> old.id))
-
-BEGIN
-  DELETE FROM $closure_table_name WHERE Id IN (
-    SELECT id FROM $closure_table_name
-    WHERE (entry_edge_id = old.id 
-    OR direct_edge_id = old.id
-    OR exit_edge_id = old.id)
-    AND (id <> old.id));
-
-END
-""")
-    return trigger_loop_NEW.substitute(closure_table_name=closure_table_name)
-
-
-def get_sqlite_tc_create_trigger_loop(links_table_name,
-                                      links_table_input_field,
-                                      links_table_output_field,
-                                      closure_table_name,
-                                      closure_table_parent_field,
-                                      closure_table_child_field):
-    from string import Template
-
-    create_trigger_loop = Template("""
-CREATE TRIGGER update_purgelist AFTER INSERT ON purge_list 
-WHEN 
-EXISTS( 
-  SELECT id FROM $closure_table_name
-    WHERE depth > 0
-    AND ( entry_edge_id IN ( SELECT Id FROM purge_list ) 
-    OR direct_edge_id IN ( SELECT Id FROM purge_list ) 
-    OR exit_edge_id IN ( SELECT Id FROM purge_list ) )
-    AND Id NOT IN (SELECT Id FROM purge_list )
-) AND EXISTS (
-  SELECT id FROM purge_list
-)
-
-BEGIN
-
-  INSERT INTO purge_list
-    SELECT id FROM $closure_table_name
-    WHERE depth > 0
-    AND ( entry_edge_id IN ( SELECT Id FROM purge_list ) 
-    OR direct_edge_id IN ( SELECT Id FROM purge_list )
-    OR exit_edge_id IN ( SELECT Id FROM purge_list ) )
-    AND Id NOT IN (SELECT Id FROM purge_list );
-
-END
-
-""")
-    return create_trigger_loop.substitute(closure_table_name=closure_table_name)
-
-
-#====================================
-#   Postgresql Transive Closure
-#====================================
-
-def get_pg_tc(links_table_name,
-              links_table_input_field,
-              links_table_output_field,
-              closure_table_name,
-              closure_table_parent_field,
-              closure_table_child_field):
-    from string import Template
-
-    pg_tc = Template("""
-
-DROP TRIGGER IF EXISTS autoupdate_tc ON $links_table_name;
-DROP FUNCTION IF EXISTS update_tc();
-
-CREATE OR REPLACE FUNCTION update_tc()
-  RETURNS trigger AS
-$$BODY$$
-DECLARE
-     
-    new_id INTEGER;
-    old_id INTEGER;
-    num_rows INTEGER;
     
-BEGIN
-
-  IF tg_op = 'INSERT' THEN
-
-    IF EXISTS (
-      SELECT Id FROM $closure_table_name
-      WHERE $closure_table_parent_field = new.$links_table_input_field
-         AND $closure_table_child_field = new.$links_table_output_field
-         AND depth = 0
-         )
-    THEN
-      RETURN null;
-    END IF;
-
-    IF new.$links_table_input_field = new.$links_table_output_field
-    OR EXISTS (
-      SELECT id FROM $closure_table_name 
-        WHERE $closure_table_parent_field = new.$links_table_output_field 
-        AND $closure_table_child_field = new.$links_table_input_field
-        )
-    THEN
-      RETURN null;
-    END IF;
-
-    INSERT INTO $closure_table_name (
-         $closure_table_parent_field,
-         $closure_table_child_field,
-         depth)
-      VALUES (
-         new.$links_table_input_field,
-         new.$links_table_output_field,
-         0);
-     
-    new_id := lastval();
-
-    UPDATE $closure_table_name
-      SET entry_edge_id = new_id
-        , exit_edge_id = new_id
-        , direct_edge_id = new_id 
-      WHERE id = new_id;
-
-
-    INSERT INTO $closure_table_name (
-      entry_edge_id,
-      direct_edge_id,
-      exit_edge_id,
-      $closure_table_parent_field,
-      $closure_table_child_field,
-      depth) 
-      SELECT id
-         , new_id
-         , new_id
-         , $closure_table_parent_field 
-         , new.$links_table_output_field
-         , depth + 1
-        FROM $closure_table_name
-        WHERE $closure_table_child_field = new.$links_table_input_field;
-
-
-    INSERT INTO $closure_table_name (
-      entry_edge_id,
-      direct_edge_id,
-      exit_edge_id,
-      $closure_table_parent_field,
-      $closure_table_child_field,
-      depth)
-      SELECT new_id
-        , new_id
-        , id 
-        , new.$links_table_input_field
-        , $closure_table_child_field
-        , depth + 1
-        FROM $closure_table_name
-        WHERE $closure_table_parent_field = new.$links_table_output_field;
-
-    INSERT INTO $closure_table_name (
-      entry_edge_id,
-      direct_edge_id,
-      exit_edge_id,
-      $closure_table_parent_field,
-      $closure_table_child_field,
-      depth)
-      SELECT A.id
-        , new_id
-        , B.id
-        , A.$closure_table_parent_field
-        , B.$closure_table_child_field
-        , A.depth + B.depth + 2
-     FROM $closure_table_name A
-        CROSS JOIN $closure_table_name B
-     WHERE A.$closure_table_child_field = new.$links_table_input_field
-       AND B.$closure_table_parent_field = new.$links_table_output_field;
-   
-  END IF;
-
-  IF tg_op = 'DELETE' THEN
-
-    IF NOT EXISTS( 
-        SELECT id FROM $closure_table_name 
-        WHERE $closure_table_parent_field = old.$links_table_input_field
-        AND $closure_table_child_field = old.$links_table_output_field AND
-        depth = 0 )
-    THEN
-        RETURN NULL;
-    END IF;
-
-    CREATE TABLE PurgeList (Id int);
-
-    INSERT INTO PurgeList
-      SELECT id FROM $closure_table_name
-          WHERE $closure_table_parent_field = old.$links_table_input_field
-        AND $closure_table_child_field = old.$links_table_output_field AND
-        depth = 0;
-          
-    WHILE (1 = 1)
-    loop
-    
-      INSERT INTO PurgeList
-        SELECT id FROM $closure_table_name
-          WHERE depth > 0
-          AND ( entry_edge_id IN ( SELECT Id FROM PurgeList ) 
-          OR direct_edge_id IN ( SELECT Id FROM PurgeList ) 
-          OR exit_edge_id IN ( SELECT Id FROM PurgeList ) )
-          AND Id NOT IN (SELECT Id FROM PurgeList );
-          
-      GET DIAGNOSTICS num_rows = ROW_COUNT;
-      if (num_rows = 0) THEN 
-        EXIT;
-      END IF;
-    end loop;
-    
-    DELETE FROM $closure_table_name WHERE Id IN ( SELECT Id FROM PurgeList);
-    DROP TABLE PurgeList;
-    
-  END IF;
-
-  RETURN NULL;
-  
-END
-$$BODY$$
-  LANGUAGE plpgsql VOLATILE
-  COST 100;
-
-
-CREATE TRIGGER autoupdate_tc
-  AFTER INSERT OR DELETE OR UPDATE
-  ON $links_table_name FOR each ROW
-  EXECUTE PROCEDURE update_tc();
-
-""")
-    return pg_tc.substitute(links_table_name=links_table_name,
-                            links_table_input_field=links_table_input_field,
-                            links_table_output_field=links_table_output_field,
-                            closure_table_name=closure_table_name,
-                            closure_table_parent_field=closure_table_parent_field,
-                            closure_table_child_field=closure_table_child_field)
-
-
-#====================================
-#   Mysql Transive Closure
-#====================================
-
-def get_mysql_trigger_update(db_name,
-                             links_table_name,
-                             links_table_input_field,
-                             links_table_output_field,
-                             closure_table_name,
-                             closure_table_parent_field,
-                             closure_table_child_field):
-    from string import Template
-
-    trigger_update = Template("""
-
-CREATE TRIGGER update_tc_insert AFTER INSERT ON $links_table_name
-FOR EACH ROW
-proc_label:BEGIN
-      
-      DECLARE new_id integer;
-
-      IF ( SELECT 1 = 1 FROM $closure_table_name
-           WHERE $closure_table_parent_field = NEW.$links_table_input_field
-             AND $closure_table_child_field = NEW.$links_table_output_field
-             AND depth = 0 )
-      THEN
-        LEAVE proc_label;
-      END IF;
-
-      IF NEW.$links_table_input_field = NEW.$links_table_output_field
-      OR ( SELECT 1=1 FROM $closure_table_name
-           WHERE $closure_table_parent_field = NEW.$links_table_output_field
-           AND $closure_table_child_field = NEW.$links_table_input_field)
-      THEN
-        LEAVE proc_label;
-      END IF;
-    
-      #START TRANSACTION ;
-      INSERT INTO $closure_table_name ( $closure_table_parent_field, $closure_table_child_field, depth)
-      VALUES ( NEW.$links_table_input_field, NEW.$links_table_output_field, 0);
-
-      SET new_id = LAST_INSERT_ID();
-
-      UPDATE $closure_table_name
-      SET entry_edge_id = new_id,
-          exit_edge_id = new_id,
-          direct_edge_id = new_id
-      WHERE id = new_id;
-
-      INSERT INTO $closure_table_name (
-        entry_edge_id,
-        direct_edge_id,
-        exit_edge_id,
-        $closure_table_parent_field,
-        $closure_table_child_field,
-        depth)
-          SELECT id
-           , new_id
-           , new_id
-           , $closure_table_parent_field
-           , NEW.$links_table_output_field
-           , depth + 1
-          FROM $closure_table_name
-          WHERE $closure_table_child_field = NEW.$links_table_input_field;
-
-      INSERT INTO $closure_table_name (
-        entry_edge_id,
-        direct_edge_id,
-        exit_edge_id,
-        $closure_table_parent_field,
-        $closure_table_child_field,
-        depth)
-        SELECT new_id
-          , new_id
-          , id
-          , NEW.$links_table_input_field
-          , $closure_table_child_field
-          , depth + 1
-          FROM $closure_table_name
-          WHERE $closure_table_parent_field = NEW.$links_table_output_field;
-
-      INSERT INTO $closure_table_name (
-        entry_edge_id,
-        direct_edge_id,
-        exit_edge_id,
-        $closure_table_parent_field,
-        $closure_table_child_field,
-        depth)
-        SELECT A.id
-          , new_id
-          , B.id
-          , A.$closure_table_parent_field
-          , B.$closure_table_child_field
-          , A.depth + B.depth + 2
-        FROM $closure_table_name A
-          CROSS JOIN $closure_table_name B
-        WHERE A.$closure_table_child_field = NEW.$links_table_input_field
-          AND B.$closure_table_parent_field = NEW.$links_table_output_field;
-
-      #COMMIT ;
-
-  #CALL `aiidadb`.`update_tc` ('INSERT', NEW.$links_table_input_field, NEW.$links_table_output_field, -1, -1);
-
-END;
-
-""")
-    return trigger_update.substitute(links_table_name=links_table_name,
-                                     links_table_input_field=links_table_input_field,
-                                     links_table_output_field=links_table_output_field,
-                                     closure_table_name=closure_table_name,
-                                     closure_table_parent_field=closure_table_parent_field,
-                                     closure_table_child_field=closure_table_child_field)
-
-
-def get_mysql_trigger_delete(db_name,
-                             links_table_name,
-                             links_table_input_field,
-                             links_table_output_field,
-                             closure_table_name,
-                             closure_table_parent_field,
-                             closure_table_child_field):
-    from string import Template
-
-    trigger_delete = Template("""
-    
-CREATE TRIGGER update_tc_delete AFTER DELETE ON $links_table_name
-FOR EACH ROW
-proc_label:BEGIN
-
-      DECLARE num_rows integer;
-
-      IF NOT ( SELECT 1=1 FROM $closure_table_name
-           WHERE $closure_table_parent_field = OLD.$links_table_input_field
-           AND $closure_table_child_field = OLD.$links_table_output_field AND
-           depth = 0 )
-      THEN
-        LEAVE proc_label;
-      END IF;
-      
-      DELETE FROM PurgeList where 1 = 1;
-      
-      INSERT INTO PurgeList
-        SELECT id FROM $closure_table_name
-        WHERE $closure_table_parent_field = OLD.$links_table_input_field
-        AND $closure_table_child_field = OLD.$links_table_output_field AND
-        depth = 0;
-
-      purge_loop: WHILE (1 = 1) DO
-
-        INSERT INTO PurgeList
-          SELECT id FROM $closure_table_name
-            WHERE depth > 0
-            AND ( entry_edge_id IN ( SELECT Id FROM PurgeList )
-            OR direct_edge_id IN ( SELECT Id FROM PurgeList )
-            OR exit_edge_id IN ( SELECT Id FROM PurgeList ) )
-            AND Id NOT IN (SELECT Id FROM PurgeList );
-
-        SET num_rows = ROW_COUNT();
-
-        if (num_rows = 0) THEN
-          LEAVE purge_loop;
-        END IF;
-
-      END WHILE;
-
-      DELETE FROM $closure_table_name WHERE Id IN ( SELECT Id FROM PurgeList);
-
-
-END;
-""")
-    return trigger_delete.substitute(links_table_name=links_table_name,
-                                     links_table_input_field=links_table_input_field,
-                                     links_table_output_field=links_table_output_field,
-                                     closure_table_name=closure_table_name,
-                                     closure_table_parent_field=closure_table_parent_field,
-                                     closure_table_child_field=closure_table_child_field)
-
-
-#====================================
-#   Installer
-#====================================
-
-def install_tc(sender, **kwargs):
-    from django.db import connection, transaction
-
-    cursor = connection.cursor()
-
-    links_table_name = "db_dblink"
-    links_table_input_field = "input_id"
-    links_table_output_field = "output_id"
-    closure_table_name = "db_dbpath"
-    closure_table_parent_field = "parent_id"
-    closure_table_child_field = "child_id"
-
-    if "mysql" in settings.DATABASES['default']['ENGINE']:
-
-        import MySQLdb
-        import warnings
-
-        warnings.filterwarnings("ignore", "PROCEDURE.*")
-
-        print '== Mysql found, installing transitive closure engine =='
-
-        #         print get_mysql_tc(settings.DATABASES['default']['NAME'], links_table_name, links_table_input_field, links_table_output_field,
-        #                                  closure_table_name, closure_table_parent_field, closure_table_child_field)
-        db_name = settings.DATABASES['default']['NAME']
-
-        print "Cleaning old triggers"
-        try:
-            cursor.execute("DROP PROCEDURE IF EXISTS `" + db_name + "`.`update_tc`;")
-        except MySQLdb.Warning:
-            pass
-        try:
-            cursor.execute("DROP TRIGGER IF EXISTS update_tc_insert;")
-        except MySQLdb.Warning:
-            pass
-
-        try:
-            cursor.execute("DROP TRIGGER IF EXISTS update_tc_delete;")
-        except MySQLdb.Warning:
-            pass
-
-        try:
-            cursor.execute("DROP TABLE IF EXISTS PurgeList;")
-        except MySQLdb.Warning:
-            pass
-
-        cursor.execute("CREATE TABLE PurgeList (Id int);")
-
-        print "Installing trigger for update"
-        cursor.execute(
-            get_mysql_trigger_update(db_name, links_table_name, links_table_input_field, links_table_output_field,
-                                     closure_table_name, closure_table_parent_field, closure_table_child_field))
-        transaction.commit_unless_managed()
-
-        print "Installing trigger for delete"
-        cursor = connection.cursor()
-        cursor.execute(
-            get_mysql_trigger_delete(db_name, links_table_name, links_table_input_field, links_table_output_field,
-                                     closure_table_name, closure_table_parent_field, closure_table_child_field))
-
-        transaction.commit_unless_managed()
-
-    elif "postgresql" in settings.DATABASES['default']['ENGINE']:
-        print '== Postgres found, installing transitive closure engine =='
-
-        cursor.execute(get_pg_tc(links_table_name, links_table_input_field, links_table_output_field,
-                                 closure_table_name, closure_table_parent_field, closure_table_child_field))
-
-        transaction.commit_unless_managed()
-    elif "sqlite3" in settings.DATABASES['default']['ENGINE']:
-        print '== SQLite3 found, installing transitive closure engine =='
-        # Use the new trigger without the support purge_list table
-
-        from django.db.backends.sqlite3.base import Database as DjDatabase
-
-        sqlite_version = DjDatabase.sqlite_version_info
-        sqlite_version_string = DjDatabase.sqlite_version
-
-        # Note: there are some problems with the new version of the triggers
-        # This problem is not shown when the tests db.nodes are run
-        # However, the execution of the test on the database (copy/paste in 
-        # the shell) does not work. The old version does not show this problem.
-        # I comment the new one until it's fixed.
-
-        #         # This is the first version that supports recursive triggers
-        #         if sqlite_version < (3, 6, 18):
-        #             new_sql_trigger = False
-        #             print r'   ||  NOTE: using old version of SQLite triggers  ||'
-        #             print r'   ||  because your sqlite version is too old:     ||'
-        #             print r'   \\  {} //'.format(
-        #                 (sqlite_version_string + ' (< 3.6.18)').ljust(43))
-        #         else:
-        #             new_sql_trigger = True
-        #             print r'   ||  NOTE: using new version of SQLite triggers  ||'
-        #             print r'   ||  because your sqlite version is sufficiently ||'
-        #             print r'   \\  recent: {} //'.format(
-        #                 (sqlite_version_string + ' (> 3.6.18)').ljust(35))
-
-        cursor.execute("DROP TRIGGER IF EXISTS update_tc;")
-        cursor.execute(
-            get_sqlite_tc_create_trigger_update(links_table_name, links_table_input_field, links_table_output_field,
-                                                closure_table_name, closure_table_parent_field,
-                                                closure_table_child_field))
-        #         if new_sql_trigger:
-        #             # the 'new' triggers work only if recursive triggers are active
-        #             # This is required for sqlite >= 3.6.18; it is the default
-        #             # from sqlite >=3.7
-        #             # NOTE: The default maximum trigger recursion depth is 1000.
-        #             # Hopefully, it is ok...
-        #             # To change, set the SQLITE_MAX_TRIGGER_DEPTH variable.
-        #             cursor.execute("PRAGMA RECURSIVE_TRIGGERS=true;")
-        #
-        #             cursor.execute("DROP TABLE IF EXISTS purge_list;")
-        #
-        #             cursor.execute("DROP TRIGGER IF EXISTS deleted_from;")
-        #             cursor.execute(get_sqlite_tc_create_trigger_delete_NEW(links_table_name, links_table_input_field, links_table_output_field,
-        #                                                                    closure_table_name, closure_table_parent_field, closure_table_child_field))
-        #
-        #             cursor.execute("DROP TRIGGER IF EXISTS purge_list.update_purgelist;")
-        #             cursor.execute("DROP TRIGGER IF EXISTS path_delete_recursive;")
-        #             cursor.execute(get_sqlite_tc_create_trigger_loop_NEW(links_table_name, links_table_input_field, links_table_output_field,
-        #                                                                  closure_table_name, closure_table_parent_field, closure_table_child_field))
-        #
-        #             transaction.commit_unless_managed()
-        #         else:
-        cursor.execute("DROP TABLE IF EXISTS purge_list;")
-        cursor.execute(
-            get_sqlite_tc_create_purgelist(links_table_name, links_table_input_field, links_table_output_field,
-                                           closure_table_name, closure_table_parent_field, closure_table_child_field))
-
-        cursor.execute("DROP TRIGGER IF EXISTS deleted_from;")
-        cursor.execute(
-            get_sqlite_tc_create_trigger_delete(links_table_name, links_table_input_field, links_table_output_field,
-                                                closure_table_name, closure_table_parent_field,
-                                                closure_table_child_field))
-
-        cursor.execute("DROP TRIGGER IF EXISTS purge_list.update_purgelist;")
-        cursor.execute("DROP TRIGGER IF EXISTS path_delete_recursive;")
-        cursor.execute(
-            get_sqlite_tc_create_trigger_loop(links_table_name, links_table_input_field, links_table_output_field,
-                                              closure_table_name, closure_table_parent_field,
-                                              closure_table_child_field))
-
-        transaction.commit_unless_managed()
-    else:
-        print '== No transitive closure installed =='
-
-## dispatch_uid used to avoid to install twice the signal if this
-## module is loaded twice (it happens e.g. when tests are run)
-from django.db.models.signals import post_migrate
-from django.apps import apps
-
-post_migrate.connect(install_tc,
-                     sender=apps.get_app_config('db'),
-                     dispatch_uid="transitive_closure_post_migrate")