Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/16954#discussion_r105714984
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
---
@@ -365,17 +385,66 @@ object TypeCoercion {
}
/**
- * Convert the value and in list expressions to the common operator type
- * by looking at all the argument types and finding the closest one that
- * all the arguments can be cast to. When no common operator type is
found
- * the original expression will be returned and an Analysis Exception
will
- * be raised at type checking phase.
+ * Handles type coercion for both IN expression with subquery and IN
+ * expressions without subquery.
+ * 1. In the first case, find the common type by comparing the left hand
side
+ * expression types against corresponding right hand side expression
derived
+ * from the subquery expression's plan output. Inject appropriate
casts in the
+ * LHS and RHS side of IN expression.
+ *
+ * 2. In the second case, convert the value and in list expressions to
the
+ * common operator type by looking at all the argument types and
finding
+ * the closest one that all the arguments can be cast to. When no
common
+ * operator type is found the original expression will be returned
and an
+ * Analysis Exception will be raised at the type checking phase.
*/
object InConversion extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan resolveExpressions {
// Skip nodes who's children have not been resolved yet.
case e if !e.childrenResolved => e
+ // Handle type casting required between value expression and
subquery output
+ // in IN subquery.
+ case i @ In(a, Seq(ListQuery(sub, children, exprId))) if !i.resolved
=>
--- End diff --
Maybe we should create a special InSubQuery expression. This looks like a
lot of work for what we are doing here.
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