Details
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Sub-task
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Status: Closed
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Blocker
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Resolution: Fixed
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0.14.0
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None
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None
Description
The stats annotation for a group-by only annotates the reduce-side row-count with the distinct values.
The map-side gets the row-count as the rows output instead of distinct * parallelism, while the reducer side gets the correct parallelism.
hive> explain select distinct L_SHIPDATE from lineitem;
Vertices:
Map 1
Map Operator Tree:
TableScan
alias: lineitem
Statistics: Num rows: 5999989709 Data size: 4745677733354 Basic stats: COMPLETE Column stats: COMPLETE
Select Operator
expressions: l_shipdate (type: string)
outputColumnNames: l_shipdate
Statistics: Num rows: 5999989709 Data size: 4745677733354 Basic stats: COMPLETE Column stats: COMPLETE
Group By Operator
keys: l_shipdate (type: string)
mode: hash
outputColumnNames: _col0
Statistics: Num rows: 5999989709 Data size: 563999032646 Basic stats: COMPLETE Column stats: COMPLETE
Reduce Output Operator
key expressions: _col0 (type: string)
sort order: +
Map-reduce partition columns: _col0 (type: string)
Statistics: Num rows: 5999989709 Data size: 563999032646 Basic stats: COMPLETE Column stats: COMPLETE
Execution mode: vectorized
Reducer 2
Reduce Operator Tree:
Group By Operator
keys: KEY._col0 (type: string)
mode: mergepartial
outputColumnNames: _col0
Statistics: Num rows: 1955 Data size: 183770 Basic stats: COMPLETE Column stats: COMPLETE
Select Operator
expressions: _col0 (type: string)
outputColumnNames: _col0
Statistics: Num rows: 1955 Data size: 183770 Basic stats: COMPLETE Column stats: COMPLETE
