Update 2022-04-01_14-38_a9422eeaae74_new_dataset_models_take_2.py

Previous code is not working. It is showing an error because the subquery is making a reference to the same table sl_columns. This code makes explicit the alias and join the tables NewColumn with the subquery.

superset/migrations/versions/2022-04-01_14-38_a9422eeaae74_new_dataset_models_take_2.py

@@ -636,20 +636,30 @@ def postprocess_columns(session: Session) -> None:
         return
 
     def get_joined_tables(offset, limit):
+        # Import aliased from sqlalchemy
+        from sqlalchemy.orm import aliased
+        # Create alias of NewColumn
+        new_column_alias = aliased(NewColumn)
+        # Get subquery and give it the alias "sl_colums_2"
+        subquery = session.query(new_column_alias).offset(offset).limit(limit).subquery(
+            "sl_columns_2")
+
         return (
             sa.join(
-                session.query(NewColumn)
-                .offset(offset)
-                .limit(limit)
-                .subquery("sl_columns"),
+                subquery,
+                NewColumn,
+                # Use column id from subquery
+                subquery.c.id == NewColumn.id
+            )  .join(
                 dataset_column_association_table,
-                dataset_column_association_table.c.column_id == NewColumn.id,
-            )
-            .join(
+                # Use column id from subquery
+                dataset_column_association_table.c.column_id == subquery.c.id,
+                )
+                .join(
                 NewDataset,
                 NewDataset.id == dataset_column_association_table.c.dataset_id,
             )
-            .join(
+                .join(
                 dataset_table_association_table,
                 # Join tables with physical datasets
                 and_(
@@ -658,15 +668,17 @@ def get_joined_tables(offset, limit):
                 ),
                 isouter=True,
             )
-            .join(Database, Database.id == NewDataset.database_id)
-            .join(
+                .join(Database, Database.id == NewDataset.database_id)
+                .join(
                 TableColumn,
-                TableColumn.uuid == NewColumn.uuid,
+                # Use column uuid from subquery
+                TableColumn.uuid == subquery.c.uuid,
                 isouter=True,
             )
-            .join(
+                .join(
                 SqlMetric,
-                SqlMetric.uuid == NewColumn.uuid,
+                # Use column uuid from subquery
+                SqlMetric.uuid == subquery.c.uuid,
                 isouter=True,
             )
         )