gene-bordegaray commented on code in PR #20331:
URL: https://github.com/apache/datafusion/pull/20331#discussion_r2801910997
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datafusion/physical-optimizer/src/enforce_distribution.rs:
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@@ -1454,21 +1481,86 @@ pub fn ensure_distribution(
plan.with_new_children(children_plans)?
};
+ // For partitioned hash joins, decide dynamic filter routing mode.
+ //
+ // Dynamic filtering requires matching partitioning schemes on both sides:
+ // - PartitionIndex: Both sides use file-grouped partitioning
(value-based).
+ // Partition i on build corresponds to partition i on probe by partition
value.
+ // - CaseHash: Both sides use hash repartitioning (hash-based).
+ // Uses CASE expression with hash(row) % N to route to correct partition
filter.
+ //
+ // NOTE: If partitioning schemes are misaligned (one file-grouped, one
hash-repartitioned),
+ // the partitioned join itself is incorrect.
+ // Partition assignments don't match:
+ // - File-grouped: partition 0 = all rows where column="A" (value-based)
+ // - Hash-repartitioned: partition 0 = all rows where hash(column) % N ==
0 (hash-based)
+ // These are incompatible, so the join will miss matching rows.
+ plan = if let Some(hash_join) =
plan.as_any().downcast_ref::<HashJoinExec>()
+ && matches!(hash_join.mode, PartitionMode::Partitioned)
+ {
+ let routing_mode = match (
+ children[0].data.repartitioned,
+ children[1].data.repartitioned,
+ ) {
+ (false, false) => DynamicFilterRoutingMode::PartitionIndex,
+ (true, true) => DynamicFilterRoutingMode::CaseHash,
+ _ => {
+ // Misaligned partitioning schemes
+ return plan_err!(
+ "Partitioned hash join has incompatible partitioning
schemes: \
+ left side is {}, right side is {}.",
+ if children[0].data.repartitioned {
+ "hash-repartitioned"
+ } else {
+ "file-grouped"
+ },
+ if children[1].data.repartitioned {
+ "hash-repartitioned"
+ } else {
+ "file-grouped"
+ }
Review Comment:
I didn't love this, maybe could have a helper to map and make it cleaner
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