Function findColFromNaturalUsingJoin

pkg/planner/core/logical_plan_builder.go:1254–1265

findColFromNaturalUsingJoin is used to recursively find the column from the underlying natural-using-join. e.g. For SQL like `select t2.a from t1 join t2 using(a) where t2.a > 0`, the plan will be `join->selection->projection`. The schema of the `selection` will be `[t1.a]`, thus we need to recursiv

(p base.LogicalPlan, col *expression.Column)

// will be `[t1.a]`, thus we need to recursively retrieve the `t2.a` from the
// underlying join.
func findColFromNaturalUsingJoin(p base.LogicalPlan, col *expression.Column) (name *types.FieldName) {
	switch x := p.(type) {
	case *logicalop.LogicalLimit, *logicalop.LogicalSelection, *logicalop.LogicalTopN, *logicalop.LogicalSort, *logicalop.LogicalMaxOneRow:
		return findColFromNaturalUsingJoin(p.Children()[0], col)
	case *logicalop.LogicalJoin:
		if x.FullSchema != nil {
			idx := x.FullSchema.ColumnIndex(col)
			return x.FullNames[idx]
		}
	}
	return nil
}

type resolveGroupingTraverseAction struct {
	CurrentBlockExpand *logicalop.LogicalExpand