agrawaldevesh commented on a change in pull request #29304:
URL: https://github.com/apache/spark/pull/29304#discussion_r464135838
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File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala
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@@ -327,11 +327,27 @@ private[joins] object UnsafeHashedRelation {
// Create a mapping of buildKeys -> rows
val keyGenerator = UnsafeProjection.create(key)
var numFields = 0
+ val nullPaddingCombinations: Seq[UnsafeProjection] = if (isNullAware) {
+ // C(numKeys, 0), C(numKeys, 1) ... C(numKeys, numKeys - 1)
+ // In total 2^numKeys - 1 records will be appended.
+ key.indices.flatMap { n =>
+ key.indices.combinations(n).map { combination =>
+ // combination is Seq[Int] indicates which key should be replaced to
null padding
+ val exprs = key.indices.map { index =>
+ if (combination.contains(index)) {
+ Literal.create(null, key(index).dataType)
Review comment:
It should be easy to fold this optimization into this PR ... All we need
to do is to only create the combinations for the (truly) nullable keys. I think
this is an important performance optimization since most keys are non nullable
(in a well formed schema) and it would reduce the memory blow up.
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