Major Description
SELECT COUNT(DISTINCT 2), COUNT(DISTINCT 2, 3) will trigger this bug.
The problematic code is:
val distinctAggGroups = aggExpressions.filter(_.isDistinct).groupBy { e =>
val unfoldableChildren = e.aggregateFunction.children.filter(!_.foldable).toSet
if (unfoldableChildren.nonEmpty) {
// Only expand the unfoldable children
unfoldableChildren
} else {
// If aggregateFunction's children are all foldable
// we must expand at least one of the children (here we take the first child),
// or If we don't, we will get the wrong result, for example:
// count(distinct 1) will be explained to count(1) after the rewrite function.
// Generally, the distinct aggregateFunction should not run
// foldable TypeCheck for the first child.
e.aggregateFunction.children.take(1).toSet
}
}
