PREHOOK: query: -- union case: both subqueries are map-reduce jobs on same input, followed by reduce sink

explain 
  select unionsrc.key, count(1) FROM (select 'tst1' as key, count(1) as value from src s1
                                    UNION  ALL  
                                      select 'tst2' as key, count(1) as value from src s2) unionsrc group by unionsrc.key
PREHOOK: type: QUERY
POSTHOOK: query: -- union case: both subqueries are map-reduce jobs on same input, followed by reduce sink

explain 
  select unionsrc.key, count(1) FROM (select 'tst1' as key, count(1) as value from src s1
                                    UNION  ALL  
                                      select 'tst2' as key, count(1) as value from src s2) unionsrc group by unionsrc.key
POSTHOOK: type: QUERY
STAGE DEPENDENCIES:
  Stage-1 is a root stage
  Stage-0 is a root stage

STAGE PLANS:
  Stage: Stage-1
    Tez
      Edges:
        Reducer 2 <- Map 1 (SIMPLE_EDGE), Union 3 (CONTAINS)
        Reducer 4 <- Union 3 (SIMPLE_EDGE)
        Reducer 6 <- Map 5 (SIMPLE_EDGE), Union 3 (CONTAINS)
#### A masked pattern was here ####
      Vertices:
        Map 1 
            Map Operator Tree:
                TableScan
                  alias: s1
                  Statistics: Num rows: 0 Data size: 5812 Basic stats: PARTIAL Column stats: COMPLETE
                  Select Operator
                    Statistics: Num rows: 0 Data size: 5812 Basic stats: PARTIAL Column stats: COMPLETE
                    Group By Operator
                      aggregations: count(1)
                      mode: hash
                      outputColumnNames: _col0
                      Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
                      Reduce Output Operator
                        sort order: 
                        Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
                        value expressions: _col0 (type: bigint)
        Map 5 
            Map Operator Tree:
                TableScan
                  alias: s2
                  Statistics: Num rows: 0 Data size: 5812 Basic stats: PARTIAL Column stats: COMPLETE
                  Select Operator
                    Statistics: Num rows: 0 Data size: 5812 Basic stats: PARTIAL Column stats: COMPLETE
                    Group By Operator
                      aggregations: count(1)
                      mode: hash
                      outputColumnNames: _col0
                      Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
                      Reduce Output Operator
                        sort order: 
                        Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
                        value expressions: _col0 (type: bigint)
        Reducer 2 
            Reduce Operator Tree:
              Group By Operator
                aggregations: count(VALUE._col0)
                mode: mergepartial
                outputColumnNames: _col0
                Select Operator
                  expressions: 'tst1' (type: string), _col0 (type: bigint)
                  outputColumnNames: _col0, _col1
                  Select Operator
                    expressions: _col0 (type: string)
                    outputColumnNames: _col0
                    Group By Operator
                      aggregations: count(1)
                      keys: _col0 (type: string)
                      mode: hash
                      outputColumnNames: _col0, _col1
                      Reduce Output Operator
                        key expressions: _col0 (type: string)
                        sort order: +
                        Map-reduce partition columns: _col0 (type: string)
                        value expressions: _col1 (type: bigint)
        Reducer 4 
            Reduce Operator Tree:
              Group By Operator
                aggregations: count(VALUE._col0)
                keys: KEY._col0 (type: string)
                mode: mergepartial
                outputColumnNames: _col0, _col1
                Statistics: Num rows: 1 Data size: 88 Basic stats: COMPLETE Column stats: COMPLETE
                Select Operator
                  expressions: _col0 (type: string), _col1 (type: bigint)
                  outputColumnNames: _col0, _col1
                  Statistics: Num rows: 1 Data size: 96 Basic stats: COMPLETE Column stats: COMPLETE
                  File Output Operator
                    compressed: false
                    Statistics: Num rows: 1 Data size: 96 Basic stats: COMPLETE Column stats: COMPLETE
                    table:
                        input format: org.apache.hadoop.mapred.TextInputFormat
                        output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
                        serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe
        Reducer 6 
            Reduce Operator Tree:
              Group By Operator
                aggregations: count(VALUE._col0)
                mode: mergepartial
                outputColumnNames: _col0
                Select Operator
                  expressions: 'tst2' (type: string), _col0 (type: bigint)
                  outputColumnNames: _col0, _col1
                  Select Operator
                    expressions: _col0 (type: string)
                    outputColumnNames: _col0
                    Group By Operator
                      aggregations: count(1)
                      keys: _col0 (type: string)
                      mode: hash
                      outputColumnNames: _col0, _col1
                      Reduce Output Operator
                        key expressions: _col0 (type: string)
                        sort order: +
                        Map-reduce partition columns: _col0 (type: string)
                        value expressions: _col1 (type: bigint)
        Union 3 
            Vertex: Union 3

  Stage: Stage-0
    Fetch Operator
      limit: -1

PREHOOK: query: select unionsrc.key, count(1) FROM (select 'tst1' as key, count(1) as value from src s1
                                  UNION  ALL  
                                    select 'tst2' as key, count(1) as value from src s2) unionsrc group by unionsrc.key
PREHOOK: type: QUERY
PREHOOK: Input: default@src
#### A masked pattern was here ####
POSTHOOK: query: select unionsrc.key, count(1) FROM (select 'tst1' as key, count(1) as value from src s1
                                  UNION  ALL  
                                    select 'tst2' as key, count(1) as value from src s2) unionsrc group by unionsrc.key
POSTHOOK: type: QUERY
POSTHOOK: Input: default@src
#### A masked pattern was here ####
tst1	1
tst2	1