leanken commented on a change in pull request #29304:
URL: https://github.com/apache/spark/pull/29304#discussion_r464159019
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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:
After serious consideration, I think when `key(index).nullable = false`
case, it should be expand as well.
Just consider the following case, with streamedSide and buildSide both has
only one record
(1, null, 3) => (1, 2, 3)
this was consider a MATCH on NAAJ, right? no matter buildSide column is
nullable or not, NAAJ care about its real key value of the record. if we don't
expand (1,2,3) to 7X record, we can't find a exact match of (1,null,3)
@maropu @agrawaldevesh
if we don't want extra if-else check on null column, it is needed to do such
expansion, because I already put all possibilities in HashedRelation,
streamedSide record just need to lookup, if you got a exact match, bingo.
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