martin-g commented on code in PR #18814:
URL: https://github.com/apache/datafusion/pull/18814#discussion_r2542100274
##########
datafusion/expr/src/logical_plan/builder.rs:
##########
@@ -1729,23 +1738,53 @@ pub fn requalify_sides_if_needed(
) -> Result<(LogicalPlanBuilder, LogicalPlanBuilder, bool)> {
let left_cols = left.schema().columns();
let right_cols = right.schema().columns();
- if left_cols.iter().any(|l| {
- right_cols.iter().any(|r| {
- l == r || (l.name == r.name && (l.relation.is_none() ||
r.relation.is_none()))
- })
- }) {
- // These names have no connection to the original plan, but they'll
make the columns
- // (mostly) unique.
- Ok((
- left.alias(TableReference::bare("left"))?,
- right.alias(TableReference::bare("right"))?,
- true,
- ))
- } else {
- Ok((left, right, false))
+
+ // Requalify if merging the schemas would cause an error during join.
+ // This can happen in several cases:
+ // 1. Duplicate qualified fields: both sides have same relation.name
+ // 2. Duplicate unqualified fields: both sides have same unqualified name
+ // 3. Ambiguous reference: one side qualified, other unqualified, same name
+ for l in &left_cols {
+ for r in &right_cols {
Review Comment:
Wow! Such an answer!
Next time just tell me "We can improve it if it ever shows up in the
profiler" 😄
Thank you!
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