Heal script: Drop fks before operating on columns

This patch fixes a small glitch in the healing script.
If the script detects that a foreign key must be removed,
and the columns that it references must be removed as well,
then the foreign key removal would fail as the column would
not exist anymore.

This patch simply ensures foreign key are dropped before all
the remaining table/column operations. New foreign keys are
instead added after all table/column operations are completed.

Change-Id: I3cce742146c70b71900cf53e50f9a6a61bc6a378
Closes-Bug: # 1354188

diff --git a/neutron/db/migration/alembic_migrations/heal_script.py b/neutron/db/migration/alembic_migrations/heal_script.py
index dacb87474203bc1e310e2a3b361eb421dbffaac8..f1735fe41723b322cc54a4d83a38e6219720f32f 100644 (file)
--- a/neutron/db/migration/alembic_migrations/heal_script.py
+++ b/neutron/db/migration/alembic_migrations/heal_script.py
@@ -73,8 +73,8 @@ def heal():
     diff1 = autogen.compare_metadata(mc, models_metadata)
     # Alembic does not contain checks for foreign keys. Because of that it
     # checks separately.
-    diff2 = check_foreign_keys(models_metadata)
-    diff = diff1 + diff2
+    added_fks, dropped_fks = check_foreign_keys(models_metadata)
+    diff = dropped_fks + diff1 + added_fks
     # For each difference run command
     for el in diff:
         execute_alembic_command(el)
@@ -205,7 +205,8 @@ def add_key(fk):
 def check_foreign_keys(metadata):
     # This methods checks foreign keys that tables contain in models with
     # foreign keys that are in db.
-    diff = []
+    added_fks = []
+    dropped_fks = []
     bind = op.get_bind()
     insp = sqlalchemy.engine.reflection.Inspector.from_engine(bind)
     # Get all tables from db
@@ -224,15 +225,15 @@ def check_foreign_keys(metadata):
                          model_tables[table].foreign_keys)
         fk_models_set = set(fk_models.keys())
         for key in (fk_db_set - fk_models_set):
-            diff.append(('drop_key', fk_db[key], table))
+            dropped_fks.append(('drop_key', fk_db[key], table))
             LOG.info(_("Detected removed foreign key %(fk)r on "
                        "table %(table)r"), {'fk': fk_db[key], 'table': table})
         for key in (fk_models_set - fk_db_set):
-            diff.append(('add_key', fk_models[key]))
+            added_fks.append(('add_key', fk_models[key]))
             LOG.info(_("Detected added foreign key for column %(fk)r on table "
                        "%(table)r"), {'fk': fk_models[key].column.name,
                                       'table': table})
-    return diff
+    return (added_fks, dropped_fks)
 
 
 def check_if_table_exists(table):