[DRILL-5395] Query on MapR-DB table fails with NPE due to an issue with assignment logic

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.9.0, 1.10.0
• Fix Version/s: 1.11.0
• Component/s: Query Planning & Optimization, Storage - MapRDB
• Labels: MapR-DB-Binary ready-to-commit
• Assignee: Padma Penumarthy
• Reporter: Abhishek Girish
• Reviewer: Chunhui Shi
• Created: 29/Mar/17 01:20
• Updated: 14/May/17 00:45
• Resolved: 08/Apr/17 12:35

Description

We uncovered this issue when working on DRILL-5394.

The MapR-DB table in question had 5 tablets with skewed data distribution (~6 million rows). A partial WIP fix for DRILL-5394 caused the number of rows to be reported incorrectly (~300,000). 2 minor fragments were created (due to filter selectivity) for scanning the 5 tablets. And this resulted in an NPE, possibly related to an issue with assignment logic, that was now exposed.

Representative query:

SELECT Convert_from(avail.customer, 'UTF8') AS ABC, 
       Convert_from(prop.customer, 'UTF8')  AS PQR 
FROM   (SELECT Convert_from(a.row_key, 'UTF8') 
               AS customer, 
               Cast(Convert_from(a.data .` l_discount ` , 'double_be') AS FLOAT) 
               AS availability 
        FROM   db.tpch_maprdb.lineitem_1 a 
        WHERE  Convert_from(a.row_key, 'UTF8') = '%004%') AS avail 
       join 
              (SELECT Convert_from(b.row_key, 'UTF8') 
                      AS customer, 
               Cast( 
       Convert_from(b.data .` l_discount ` , 'double_be') AS FLOAT) AS 
               availability 
        FROM   db.tpch_maprdb.lineitem_1 b 
        WHERE  Convert_from(b.row_key, 'UTF8') LIKE '%003%') AS prop 
         ON avail.customer = prop.customer; 

Error:

org.apache.drill.common.exceptions.UserException: SYSTEM ERROR: NullPointerException

Log attached.

Issue Links

• links to: GitHub Pull Request #803