[DRILL-3476] Filter on nested element gives wrong results

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 1.2.0
• Assignee: Chun Chang
• Reporter: Steven Phillips
• Created: 09/Jul/15 01:23
• Updated: 01/Jun/18 17:26
• Resolved: 29/Jul/15 13:46

Description

Take this query for example:

0: jdbc:drill:drillbit=localhost> select * from t;
+----------------+
|       a        |
+----------------+
| {"b":1,"c":1}  |
+----------------+

if I instead run:

0: jdbc:drill:drillbit=localhost> select a from t where t.a.b = 1;
+----------------+
|       a        |
+----------------+
| {"b":1}  |
+----------------+

Only a.b was returned, but the select specified a. In this case, it should have returned all of the elements of a, not just the one specified in the filter.

This is because the logic in FieldSelection does not correctly handle the case where a selected column is a child of another selected column. In such a case, the record reader should ignore the child column, and just return the full selected parent column.

Issue Links

• is related to: DRILL-3550 Incorrect results reading complex data with schema change
• is related to: DRILL-3551 CTAS from complex Json source with schema change is not written (and hence not read back ) correctly
• links to: GitHub Pull Request #83