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| author | Takeshi YAMAMURO <linguin.m.s@gmail.com> | 2016-12-22 01:53:33 +0100 |
|---|---|---|
| committer | Herman van Hovell <hvanhovell@databricks.com> | 2016-12-22 01:53:33 +0100 |
| commit | b41ec997786e2be42a8a2a182212a610d08b221b (patch) | |
| tree | 7f60e50dedd0407d6a4a4316241228e064602723 /build | |
| parent | 83a6ace0d1be44f70e768348ae6688798c84343e (diff) | |
| download | spark-b41ec997786e2be42a8a2a182212a610d08b221b.tar.gz spark-b41ec997786e2be42a8a2a182212a610d08b221b.tar.bz2 spark-b41ec997786e2be42a8a2a182212a610d08b221b.zip | |
[SPARK-18528][SQL] Fix a bug to initialise an iterator of aggregation buffer
## What changes were proposed in this pull request?
This pr is to fix an `NullPointerException` issue caused by a following `limit + aggregate` query;
```
scala> val df = Seq(("a", 1), ("b", 2), ("c", 1), ("d", 5)).toDF("id", "value")
scala> df.limit(2).groupBy("id").count().show
WARN TaskSetManager: Lost task 0.0 in stage 9.0 (TID 8204, lvsp20hdn012.stubprod.com): java.lang.NullPointerException
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIterator.agg_doAggregateWithKeys$(Unknown Source)
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIterator.processNext(Unknown Source)
```
The root culprit is that [`$doAgg()`](https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/HashAggregateExec.scala#L596) skips an initialization of [the buffer iterator](https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/HashAggregateExec.scala#L603); `BaseLimitExec` sets `stopEarly=true` and `$doAgg()` exits in the middle without the initialization.
## How was this patch tested?
Added a test to check if no exception happens for limit + aggregates in `DataFrameAggregateSuite.scala`.
Author: Takeshi YAMAMURO <linguin.m.s@gmail.com>
Closes #15980 from maropu/SPARK-18528.
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