Github user junegunn commented on the issue:
https://github.com/apache/spark/pull/16347
Hive makes sure that the output file is properly sorted by the column
specified in `SORT BY` clause by having only one reduce task (output) for each
partition.
```
STAGE PLANS:
Stage: Stage-1
Map Reduce
Map Operator Tree:
TableScan
alias: __________________
Statistics: Num rows: 183663543 Data size: 313697356092 Basic
stats: COMPLETE Column stats: PARTIAL
Select Operator
expressions: __ (type: bigint), ________ (type: string), ___
(type: string), _________ (type: string), _______________ (type: string),
_______ (type: string), _____________ (type: string), ________ (type: string),
__ (type: string), _________ (type: string), ________ (type: string),
_______________ (type: string), _____________ (type: string), _____________
(type: string), ____________ (type: string), __________ (type: string), _____
(type: string), __________________ (type: string), ___ (type: string)
outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5,
_col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15,
_col16, _col17, _col18
Statistics: Num rows: 183663543 Data size: 313697356092 Basic
stats: COMPLETE Column stats: PARTIAL
Reduce Output Operator
key expressions: _col0 (type: bigint)
sort order: +
Map-reduce partition columns: _col18 (type: string)
Statistics: Num rows: 183663543 Data size: 313697356092
Basic stats: COMPLETE Column stats: PARTIAL
value expressions: _col1 (type: string), _col2 (type:
string), _col3 (type: string), _col4 (type: string), _col5 (type: string),
_col6 (type: string), _col7 (type: string), _col8 (type: string), _col9 (type:
string), _col10 (type: string), _col11 (type: string), _col12 (type: string),
_col13 (type: string), _col14 (type: string), _col15 (type: string), _col16
(type: string), _col17 (type: string), _col18 (type: string)
Execution mode: vectorized
Reduce Operator Tree:
Select Operator
expressions: KEY.reducesinkkey0 (type: bigint), VALUE._col0
(type: string), VALUE._col1 (type: string), VALUE._col2 (type: string),
VALUE._col3 (type: string), VALUE._col4 (type: string), VALUE._col5 (type:
string), VALUE._col6 (type: string), VALUE._col7 (type: string), VALUE._col8
(type: string), VALUE._col9 (type: string), VALUE._col10 (type: string),
VALUE._col11 (type: string), VALUE._col12 (type: string), VALUE._col13 (type:
string), VALUE._col14 (type: string), VALUE._col15 (type: string), VALUE._col16
(type: string), VALUE._col17 (type: string)
outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5,
_col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15,
_col16, _col17, _col18
Statistics: Num rows: 183663543 Data size: 33794091912 Basic
stats: COMPLETE Column stats: PARTIAL
File Output Operator
compressed: false
Statistics: Num rows: 183663543 Data size: 33794091912 Basic
stats: COMPLETE Column stats: PARTIAL
table:
input format:
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat
output format:
org.apache.hadoop.hive.ql.io.orc.OrcOutputFormat
serde: org.apache.hadoop.hive.ql.io.orc.OrcSerde
name: _______________.________________
```
The later stage simply moves the files to the corresponding directories.
Since the patch no longer merges and I think I have made my point, I'm
closing this.
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