[IMPALA-11712] Sort out column masking with complex types

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Frontend
• Epic Color: ghx-label-9
• Assignee: Unassigned
• Reporter: Daniel Becker
• Created: 08/Nov/22 15:41
• Updated: 08/Nov/22 15:41

Description

We determine whether a SlotDescriptor created from a star expanded path should be registered for column masking based on the path of the star item:

Empty matched types means this is expanded from star of a catalog table.
For star of complex types, e.g. my_struct., my_array., my_map.*, the matched
types will have the complex type so it's not empty.

https://github.com/apache/impala/blob/b28da054f3595bb92873433211438306fc22fbc7/fe/src/main/java/org/apache/impala/analysis/SelectStmt.java#L659

However, this comment may be wrong because in the query                                          

select a.* from mix_struct_array t, t.struct_in_arr a;

getMatchedTypes() returns an empty list for the star path even though it is not from a catalog table.

We should also find out whether we can determine from the expanded path alone (and not the path of the star item) whether we need to register it for column masking, for example by checking if it is within a complex type.