jayzhan211 commented on code in PR #25255:
URL: https://github.com/apache/datafusion/pull/25255#discussion_r4005705470
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datafusion/physical-plan/src/joins/hash_join/exec.rs:
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@@ -2512,6 +2540,74 @@ mod proto_tests {
}
}
+/// Output column index of a join, mapped to the equivalent join-key expression
+/// on the other side of the join (in that side's input schema).
+type KeyTransferMap = HashMap<usize, PhysicalExprRef>;
+
+fn is_column_at(expr: &PhysicalExprRef, index: usize) -> bool {
+ expr.downcast_ref::<Column>()
+ .is_some_and(|column| column.index() == index)
+}
+
+/// Marks every parent filter whose columns are all join keys in `key_map` as
+/// supported for `child`, rewritten over the other side's key expressions.
+///
+/// Filters `child` already accepts directly are left alone, as are filters
+/// that reference a non-key column or no column at all: the former cannot be
+/// expressed on the other side, the latter were already routed by the plain
+/// column analysis.
+fn transfer_key_filters(
+ parent_filters: &[Arc<dyn PhysicalExpr>],
+ key_map: &KeyTransferMap,
+ child: &mut ChildFilterDescription,
+) -> Result<()> {
+ if key_map.is_empty() {
+ return Ok(());
+ }
+ for (filter, pushed) in
parent_filters.iter().zip(child.parent_filters.iter_mut()) {
+ if matches!(pushed.discriminant, PushedDown::Yes) {
+ continue;
+ }
+ if let Some(transferred) = transfer_filter_across_keys(filter,
key_map)? {
+ *pushed = PushedDownPredicate::supported(transferred);
+ }
+ }
+ Ok(())
+}
+
+/// Rewrites `filter` over the other side's join keys, or returns `None` when
+/// it references a column that is not a transferable key, or no column.
+///
+/// A [`DynamicFilterPhysicalExpr`] comes out as a view sharing the original's
+/// state with its key columns remapped, so it keeps tracking the build side.
+fn transfer_filter_across_keys(
Review Comment:
type check included in key_transfer_maps
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