viirya commented on a change in pull request #25204: [SPARK-28441][SQL][Python]
Fix error when non-foldable expression is used in correlated scalar subquery
URL: https://github.com/apache/spark/pull/25204#discussion_r306359237
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/subquery.scala
##########
@@ -316,25 +316,46 @@ object RewriteCorrelatedScalarSubquery extends
Rule[LogicalPlan] {
newExpression.asInstanceOf[E]
}
+ private def removeAlias(expr: Expression): Expression = expr match {
+ case Alias(c, _) => removeAlias(c)
+ case _ => expr
+ }
+
/**
* Statically evaluate an expression containing zero or more placeholders,
given a set
- * of bindings for placeholder values.
+ * of bindings for placeholder values, if the expression is evaluable. If it
is not,
+ * bind statically evaluated expression results to an expression.
*/
- private def evalExpr(expr: Expression, bindings: Map[ExprId, Option[Any]]) :
Option[Any] = {
+ private def bindingExpr(
+ expr: Expression,
+ bindings: Map[ExprId, Option[Expression]]): Option[Expression] = {
val rewrittenExpr = expr transform {
case r: AttributeReference =>
bindings(r.exprId) match {
- case Some(v) => Literal.create(v, r.dataType)
+ case Some(v) => v
case None => Literal.default(NullType)
}
}
- Option(rewrittenExpr.eval())
+
+ // Removes Alias over given expression, because Alias is not foldable.
+ if (!removeAlias(rewrittenExpr).foldable) {
+ // SPARK-28441: Some expressions, like PythonUDF, can't be statically
evaluated.
+ // Needs to evaluate them on query runtime.
+ Some(rewrittenExpr)
+ } else {
+ val exprVal = rewrittenExpr.eval()
+ if (exprVal == null) {
+ None
Review comment:
I think it uses None to make checking bindings easier.
In other way, to use null literal, `Option[Expression]` can be changed to
`Expression` in methods like `evalSubqueryOnZeroTups`, `evalPlan`. Then we
check bindings by literal instead of None. Good thing is we can write
`Literal.create(rewrittenExpr.eval(), expr.dataType)`, instead of checking
null. Looks like just a choice problem.
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