bersprockets commented on a change in pull request #35047:
URL: https://github.com/apache/spark/pull/35047#discussion_r779885175
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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@@ -3380,6 +3380,17 @@ object SQLConf {
.checkValue(_ >= 0, "The value must be non-negative.")
.createWithDefault(8)
+ val HASHED_RELATION_REORDER_FACTOR =
buildConf("spark.sql.hashedRelationReorderFactor")
+ .doc("The HashedRelation will be reordered if the number of unique keys
times this factor is " +
+ "less than equal to the total number of rows in the HashedRelation. " +
+ "The reordering places all rows with the same key adjacent to each other
to improve " +
+ "spatial locality. This provides a performance boost while iterating
over the rows for a " +
+ "given key due to increased cache hits")
+ .version("3.3.0")
+ .doubleConf
+ .checkValue(_ > 1, "The value must be greater than 1.")
+ .createOptional
Review comment:
Maybe a default hash reorder factor of 4, but a separate config for
on/off (off would mean the reorder factor gets passed to the various hash
relation factories as None, regardless of the setting of
spark.sql.hashedRelationReorderFactor).
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