[IMPALA-4269] Codegen for Merging-Exchange node

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: Impala 2.8.0
• Fix Version/s: Impala 2.8.0
• Component/s: Backend
• Labels: codegen
• Assignee: Michael Ho
• Reporter: Michael Ho
• Created: 10/Oct/16 18:53
• Updated: 30/Aug/18 18:50
• Resolved: 20/Oct/16 06:04

Description

We should codegen the TupleRowComparator for merging-exchange operator. This should help a lot for queries such as:

SELECT *
FROM   (SELECT Rank()
                 OVER(
                   ORDER BY  l_orderkey) AS rank
        FROM   lineitem
        WHERE  l_shipdate < '1992-05-09') a
WHERE  rank < 10;

 03:SELECT  
 |  predicates: rank() < 10
 |
 02:ANALYTIC
 |  functions: rank()
 |  order by: l_orderkey ASC  
 |  window: RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
 |  
 04:MERGING-EXCHANGE [UNPARTITIONED]
 |  order by: l_orderkey ASC 
 | 
 01:SORT
 |  order by: l_orderkey ASC 
 | 
 00:SCAN HDFS [tpch_parquet.lineitem] 
   partitions=1/1 files=3 size=193.61MB
   predicates: l_shipdate < '1992-05-09'