[jira] [Created] (DRILL-4181) Improve memory limit assignment for Sort operators

["Aman Sinha (JIRA)" <ji...@apache.org>]

Aman Sinha created DRILL-4181:
---------------------------------

             Summary: Improve memory limit assignment for Sort operators
                 Key: DRILL-4181
                 URL: https://issues.apache.org/jira/browse/DRILL-4181
             Project: Apache Drill
          Issue Type: Improvement
    Affects Versions: 1.4.0
            Reporter: Aman Sinha


Currently, the max_query_memory_per_node is divided among all the Sort operators in the query plan, regardless of whether the Sort operators are executing at the same time.  Since Sort is a blocking operator, the number of concurrent Sorts running is limited.  Thus, the Sort on both sides of a MergeJoin could be concurrently executing but a Sort that occurs above the MergeJoin cannot start until the MergeJoin produces a row which is only when both the child Sorts have produced a row. 

Due to the conservative estimate, we have seen queries such as TPC-H Q8 with forced MergeJoin run out-of-memory even with high max_query_memory_per_node.  This query plan has 15 Sort operators and with max_width = 23,  max_query_memory_per_node = 20GB, each Sort gets only  63MB (20GB/(23*15)).    We should improve the algorithm for computing the memory limit. 



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)