LiaCastaneda commented on code in PR #19856:
URL: https://github.com/apache/datafusion/pull/19856#discussion_r2821386586
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datafusion/substrait/src/logical_plan/consumer/utils.rs:
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@@ -396,10 +433,25 @@ impl NameTracker {
&mut self,
expr: Expr,
) -> datafusion::common::Result<Expr> {
- match self.get_unique_name(expr.name_for_alias()?) {
- (_, NameTrackerStatus::NeverSeen) => Ok(expr),
- (name, NameTrackerStatus::SeenBefore) => Ok(expr.alias(name)),
+ if !self.would_conflict(&expr) {
+ self.insert(&expr);
+ return Ok(expr);
}
+
+ // Name collision - need to generate a unique alias
+ let schema_name = expr.schema_name().to_string();
+ let mut counter = 0;
+ let candidate_name = loop {
+ let candidate_name = format!("{schema_name}__temp__{counter}");
Review Comment:
There is also some logic to rename aliases to make them unique (used for
avoiding duplicate names in join schemas
[here](https://github.com/apache/datafusion/blob/468b690d71350bc19c7e7bafd5dc61800973d91e/datafusion/expr/src/logical_plan/builder.rs#L1591)
and
[here](https://github.com/apache/datafusion/blob/468b690d71350bc19c7e7bafd5dc61800973d91e/datafusion/expr/src/logical_plan/builder.rs#L1760))
This generates plans with `:N` suffixes like
[this](https://github.com/apache/datafusion/blob/468b690d71350bc19c7e7bafd5dc61800973d91e/datafusion/substrait/tests/cases/consumer_integration.rs#L614),
but this operates on Arrow `Fields` rather than `Expr`, so it can't be easily
unified with the `__temp__` mechanism. Maybe a future consistency improvement
could standardize on one naming convention (using `__temp__{N}` everywhere),
though probably the current distinction may be intentional (`__temp__` =
substrait conversion, `:N` = standard deduplication)?
(I'm not suggesting any change with this, it's an open question if it makes
sense)
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