wackywendell commented on code in PR #11636:
URL: https://github.com/apache/datafusion/pull/11636#discussion_r1690203149
##########
datafusion/sql/src/unparser/plan.rs:
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@@ -582,9 +558,89 @@ impl Unparser<'_> {
}
}
+ /// Convert the components of a USING clause to the USING AST
+ fn join_using_to_sql(
+ &self,
+ join_conditions: &[(Expr, Expr)],
+ ) -> Result<ast::JoinConstraint> {
+ let mut idents = Vec::with_capacity(join_conditions.len());
+ for (left, right) in join_conditions {
+ match (left, right) {
+ (
+ Expr::Column(Column {
+ relation: _,
+ name: left_name,
+ }),
+ Expr::Column(Column {
+ relation: _,
+ name: right_name,
+ }),
+ ) => {
+ if left_name != right_name {
+ // USING is only valid when the column names are the
+ // same, so they should never be different
+ return not_impl_err!(
+ "Unsupported USING with different column names"
+ );
Review Comment:
So I thought about this some more - these two cases should be impossible for
a `LogicalPlan` made from SQL (you can't do `JOIN … USING (t1.a = t1.b)`, but
could be created by a user directly creating a `LogicalPlan::Join(Join { … })`.
Given that, fallback makes sense, and I'll add a comment to explain.
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