peter-toth commented on code in PR #10832:
URL: https://github.com/apache/datafusion/pull/10832#discussion_r1632287690
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datafusion/optimizer/src/common_subexpr_eliminate.rs:
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@@ -801,15 +814,19 @@ impl TreeNodeRewriter for CommonSubexprRewriter<'_> {
let expr_name = expr.display_name()?;
self.common_exprs.insert(expr_id.clone(), expr);
+
// Alias this `Column` expr to it original "expr name",
// `projection_push_down` optimizer use "expr name" to eliminate
useless
// projections.
// TODO: do we really need to alias here?
Review Comment:
Now that aliasing looks good, can you please remove this comment?
I'm not sure that other comment regarding `projection_push_down` is still
valid. IMO a general comment like "if there is an alias ancestor node we don't
need to alias the extracted common expression" would be better.
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