viirya commented on a change in pull request #26461: [SPARK-29831][SQL] Scan
Hive partitioned table should not dramatically increase data parallelism
URL: https://github.com/apache/spark/pull/26461#discussion_r344873800
##########
File path: sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveUtils.scala
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@@ -155,6 +155,16 @@ private[spark] object HiveUtils extends Logging {
.booleanConf
.createWithDefault(true)
+ val HIVE_TABLE_SCAN_MAX_PARALLELISM =
buildConf("spark.sql.hive.tableScan.maxParallelism")
+ .doc("When reading Hive partitioned table, the default parallelism is the
sum of Hive " +
+ "partition RDDs' parallelism. For Hive table of many partitions with
many files, " +
+ "the parallelism could be very big and not good for Spark job
scheduling. This optional " +
+ "config can set a maximum parallelism for reading Hive partitioned
table. If the result " +
+ "RDD of reading such table is larger than this value, Spark will reduce
the partition " +
+ "number by doing a coalesce on the RDD.")
+ .intConf
+ .createOptional
Review comment:
The reason I leave it optional is to allow us keep current behavior.
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