Krisztian Kasa created HIVE-25369:
-------------------------------------

             Summary: Handle Sum0 when rebuilding materialized view 
incrementally
                 Key: HIVE-25369
                 URL: https://issues.apache.org/jira/browse/HIVE-25369
             Project: Hive
          Issue Type: Improvement
          Components: CBO, Materialized views
            Reporter: Krisztian Kasa
            Assignee: Krisztian Kasa


When rewriting MV insert overwrite plan to incremental rebuild plan a Sum0 
aggregate function is used when aggregating count function subresults coming 
from the existing MV data and the aggregated newly inserted/deleted records 
since the last rebuild
{code}
create materialized view mat1 stored as orc TBLPROPERTIES 
('transactional'='true') as
select t1.a, count(*) from t1
{code}
Insert overwrite plan:
{code}
HiveAggregate(group=[{0}], agg#0=[$SUM0($1)])
  HiveUnion(all=[true])
    HiveAggregate(group=[{0}], agg#0=[count()])
      HiveProject($f0=[$0])
        HiveFilter(condition=[<(2, $5.writeid)])
          HiveTableScan(table=[[default, t1]], table:alias=[t1])
    HiveTableScan(table=[[default, mat1]], table:alias=[default.mat1])
{code}



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