cql: raise when a model sync requires PK changes

PYTHON-532

cassandra/cqlengine/management.py

@@ -161,7 +161,6 @@ def sync_table(model):
         for udt in [u for u in udts if u not in syncd_types]:
             _sync_type(ks_name, udt, syncd_types)
 
-    # check for an existing column family
     if raw_cf_name not in tables:
         log.debug("sync_table creating new table %s", cf_name)
         qs = _get_create_table(model)
@@ -175,32 +174,36 @@ def sync_table(model):
                 raise
     else:
         log.debug("sync_table checking existing table %s", cf_name)
-        # see if we're missing any columns
         table_meta = tables[raw_cf_name]
-        field_names = _get_non_pk_field_names(tables[raw_cf_name])
+        table_columns = table_meta.columns
         model_fields = set()
         # # TODO: does this work with db_name??
-        for name, col in model._columns.items():
-            if col.primary_key or col.partition_key:
-                continue  # we can't mess with the PK
-            model_fields.add(name)
-            if col.db_field_name in field_names:
-                col_meta = table_meta.columns[col.db_field_name]
+        for model_name, col in model._columns.items():
+            db_name = col.db_field_name
+            model_fields.add(db_name)
+            if db_name in table_columns:
+                col_meta = table_columns[db_name]
 
                 if col_meta.cql_type != col.db_type:
-                    msg = 'Existing table {0} has column "{1}" with a type ({2}) differing from the model type ({3}).' \
-                          ' Model should be updated.'.format(cf_name, col.db_field_name, col_meta.cql_type, col.db_type)
-                    warnings.warn(msg)
-                    log.warning(msg)
-                continue  # skip columns already defined
+                    if col.primary_key or col.partition_key:
+                        raise CQLEngineException("Table {0} already exists, but has different types for primary key column '{1}' ({2}) (model field '{3}' ({4})). "
+                                                 "Update the model or remove the table.".format(cf_name, db_name, col_meta.cql_type, model_name, col.db_type))
+                    else:
+                        msg = 'Existing table {0} has column "{1}" with a type ({2}) differing from the model type ({3}).' \
+                              ' Model should be updated.'.format(cf_name, db_name, col_meta.cql_type, col.db_type)
+                        warnings.warn(msg)
+                        log.warning(msg)
+                continue
+
+            if col.primary_key or col.primary_key:
+                raise CQLEngineException("Cannot add primary key '{0}' (with db_field '{1}') to existing table {2}".format(model_name, db_name, cf_name))
 
-            # add missing column using the column def
             query = "ALTER TABLE {0} add {1}".format(cf_name, col.get_column_def())
             execute(query)
 
-        db_fields_not_in_model = model_fields.symmetric_difference(field_names)
+        db_fields_not_in_model = model_fields.symmetric_difference(table_columns)
         if db_fields_not_in_model:
-            log.info("Table %s has fields not referenced by model: %s", cf_name, db_fields_not_in_model)
+            log.info("Table {0} has fields not referenced by model: {1}".format(cf_name, db_fields_not_in_model))
 
         _update_options(model)
 
@@ -339,13 +342,6 @@ def _get_create_table(model):
     return ' '.join(query_strings)
 
 
-def _get_non_pk_field_names(table_meta):
-    # returns all fields that aren't part of the PK
-    pk_names = set(col.name for col in table_meta.primary_key)
-    field_names = [name for name in table_meta.columns.keys() if name not in pk_names]
-    return field_names
-
-
 def _get_table_metadata(model):
     # returns the table as provided by the native driver for a given model
     cluster = get_cluster()