Xuanwo commented on code in PR #23738:
URL: https://github.com/apache/datafusion/pull/23738#discussion_r3635581352
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datafusion/sql/src/unparser/plan.rs:
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@@ -115,6 +115,7 @@ impl Unparser<'_> {
| LogicalPlan::Aggregate(_)
| LogicalPlan::Sort(_)
| LogicalPlan::Join(_)
+ | LogicalPlan::AsOfJoin(_)
Review Comment:
Yes, the execution algorithm should remain a physical decision.
The separate logical node represents different relational semantics: for
left `ts = 10` and right `ts = {1, 5}`, a regular `>=` join returns both rows,
while ASOF returns only 5. Replacing a regular Join’s physical algorithm with
`AsOfJoinExec` would therefore change results.
The current implementation also needs ASOF-specific cardinality, type
coercion, projection/filter pushdown, and must not participate in ordinary join
reordering or input swapping. The logical node can still map to different
physical implementations—ordered merge now, indexed probe later.
We could instead add an explicit match mode to Join, but then every generic
join rule would need to account for it. I currently prefer a separate node for
isolation, but I’m open to a generalized representation if that is preferred.
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