eejbyfeldt commented on code in PR #13134:
URL: https://github.com/apache/datafusion/pull/13134#discussion_r1819669249
##########
datafusion/expr/src/logical_plan/builder.rs:
##########
@@ -1324,6 +1325,25 @@ pub fn change_redundant_column(fields: &Fields) ->
Vec<Field> {
})
.collect()
}
+
+fn mark_field(schema: &DFSchema) -> (Option<TableReference>, Arc<Field>) {
+ let mut table_references = schema
+ .iter()
+ .filter_map(|(qualifier, _)| qualifier)
+ .collect::<Vec<_>>();
+ table_references.dedup();
+ let table_reference = if table_references.len() == 1 {
+ table_references.pop().cloned()
+ } else {
+ None
+ };
+
+ (
+ table_reference,
+ Arc::new(Field::new("mark", DataType::Boolean, false)),
Review Comment:
The way the join is used from decorrelate subqueries it will never conflict
as that uses a subquery alias (that is prefixed __) and the new code will then
use that for the mark column as well.
But if some uses LeftMark in a query without an alias it would be able to
conflict. But I don't think just adding `__` would be a perfect fix. As it can
still conflict with it self if you have multiple joins. But also if you are
using a `LeftMark` join you will probably like to refer to the mark column and
naming it `__mark` make it look like an internal name.
One option could be to make the output column name be part of of the
`JoinType` e.g `LeftMark(Column)` and then use that for the output. Then each
user would need to make sure that name is sufficiently unique.
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