Github user chenghao-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/9480#discussion_r44099965
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
---
@@ -151,6 +164,30 @@ abstract class Expression extends TreeNode[Expression]
{
}
/**
+ * Returns the hash for this expression. Expressions that compute the
same result, even if
+ * they differ cosmetically should return the same hash.
+ */
+ def semanticHash() : Int = {
--- End diff --
Identical hash values doesn't mean the identical values, I am suggesting to
use the `hashCode` plus `semanticEquals` to identity the common expression,
that's also the motivation of `semanticEquals`. See `AttributeReference` for
details.
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