Github user dilipbiswal commented on a diff in the pull request:
https://github.com/apache/spark/pull/17330#discussion_r106795763
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/subquery.scala
---
@@ -61,6 +63,37 @@ abstract class SubqueryExpression(
}
}
+/**
+ * This expression is used to represent any form of subquery expression
namely
+ * ListQuery, Exists and ScalarSubquery. This is only used to make sure the
+ * expression equality works properly when LogicalPlan.sameResult is called
+ * on plans containing SubqueryExpression(s). This is only a transient
expression
+ * that only lives in the scope of sameResult function call. In other
words, analyzer,
+ * optimizer or planner never sees this expression type during
transformation of
+ * plans.
+ */
+case class CanonicalizedSubqueryExpr(expr: SubqueryExpression)
+ extends UnaryExpression with Unevaluable {
+ override def dataType: DataType = expr.dataType
+ override def nullable: Boolean = expr.nullable
+ override def child: Expression = expr
+ override def toString: String =
s"CanonicalizedSubqueryExpr(${expr.toString})"
+
+ // Hashcode is generated conservatively for now i.e it does not include
the
+ // sub query plan. Doing so causes issue when we canonicalize
expressions to
+ // re-order them based on hashcode.
+ // TODO : improve the hashcode generation by considering the plan info.
+ override def hashCode(): Int = {
+ val h = Objects.hashCode(expr.children)
+ h * 31 + Objects.hashCode(this.getClass.getName)
+ }
+
+ override def equals(o: Any): Boolean = o match {
+ case n: CanonicalizedSubqueryExpr => expr.semanticEquals(n.expr)
+ case other => false
--- End diff --
@gatorsmile Will change. Thanks.
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