[FSTORE-1181] Helper columns should return all columns if they have different names across feature groups (#341)

Helper columns should return all columns if they have different names across feature groups

Author: davitbzh

docs/user_guides/fs/feature_view/batch-data.md

@@ -32,7 +32,8 @@ To retrieve the primary key(s) and/or event time when retrieving batch data for
     ) # return a dataframe with primary keys and event time
     ```
 !!! note
-    If the event time columns have the same name across all the feature groups included in the feature view, then only the event time of the label feature group (left most feature group in the query) will be returned. If they have different names, then all of them will be returned. The Join prefix does not have any influence on this behaviour.
+    All primary and event time columns of all the feature groups included in the feature view will be returned. If they have the same names across feature groups and the join prefix was not provided then reading operation will fail with ambiguous column exception.
+    Make sure to define the join prefix if primary key and event time columns have the same names across feature groups.
 
 For Python-clients, handling small or moderately-sized data, we recommend enabling the [ArrowFlight Server with DuckDB](../../../setup_installation/common/arrow_flight_duckdb.md), which will provide significant speedups over Spark/Hive for reading batch data.
 If the service is enabled, and you want to read this particular batch data with Hive instead, you can set the read_options to `{"use_hive": True}`.

docs/user_guides/fs/feature_view/training-data.md

@@ -108,7 +108,8 @@ X_train, X_test, y_train, y_test = feature_view.get_train_test_split(training_da
 ```
 
 !!! note
-    If the event time columns have the same name across all the feature groups included in the feature view, then only the event time of the label feature group (left most feature group in the query) will be returned. If they have different names, then all of them will be returned. The Join prefix does not have any influence on this behaviour.
+    All primary and event time columns of all the feature groups included in the feature view will be returned. If they have the same names across feature groups and the join prefix was not provided then reading operation will fail with ambiguous column exception.
+    Make sure to define the join prefix if primary key and event time columns have the same names across feature groups. 
 
     To use primary key(s) and event time column with materialized training datasets it needs to be created with `primary_keys=True` and/or `with_event_time=True`.