vbarua commented on code in PR #17299:
URL: https://github.com/apache/datafusion/pull/17299#discussion_r2323680328
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datafusion/substrait/src/logical_plan/consumer/rel/project_rel.rs:
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@@ -62,7 +62,17 @@ pub async fn from_project_rel(
// to transform it into a column reference
window_exprs.insert(e.clone());
}
- explicit_exprs.push(name_tracker.get_uniquely_named_expr(e)?);
+ // Since substrait removes aliases, we need to assign literals
with a UUID alias to avoid
+ // ambiguous names when the same literal is used before and after
a join.
Review Comment:
> which means literals columns are just assigned their default names
Ok yeah, I figured there was some sort of default name thing going on.
Another way to phrase this might be:
> Substrait plans are ordinal based, so they do not provide names for
columns. Names for columns are generated by Datafusion during conversion, and
for literals Datafusion produces names based on the literal value. It is
possible to construct valid Substrait plans that result in duplicated names if
the same literal value is used in multiple relations. To avoid this issue, we
alias literals with unique names.
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