Vinitha Reddy Gankidi created SPARK-22411:
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Summary: Heuristic to combine splits in DataSourceScanExec isn't
accurate when dynamic allocation is enabled
Key: SPARK-22411
URL: https://issues.apache.org/jira/browse/SPARK-22411
Project: Spark
Issue Type: Bug
Components: SQL
Affects Versions: 2.0.0
Reporter: Vinitha Reddy Gankidi
Priority: Major
The heuristic to calculate the maxSplitSize in DataSourceScanExec is as follows:
https://github.com/apache/spark/blob/d28d5732ae205771f1f443b15b10e64dcffb5ff0/sql/core/src/main/scala/org/apache/spark/sql/execution/DataSourceScanExec.scala#L431
Default parallelism in this case is the number of total cores of all the
registered executors for this application. This works well with static
allocation but with dynamic allocation enabled, this value is usually one (with
default config of min and initial executors as zero) at the time of split
calculation. This heuristic was introduced in SPARK-14582.
When Dynamic allocation it is confusing to tune the split size with this
heuristic. It is better to ignore bytesPerCore and use the values of
'spark.sql.files.maxPartitionBytes' as the max split size.
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