adriangb commented on code in PR #17197:
URL: https://github.com/apache/datafusion/pull/17197#discussion_r2288174136
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datafusion/physical-plan/src/joins/hash_join.rs:
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@@ -1695,12 +1858,91 @@ impl HashJoinStream {
.get_shared(cx))?;
build_timer.done();
+ // Handle dynamic filter bounds accumulation
+ //
+ // This coordination ensures the dynamic filter contains complete
bounds information
+ // from all relevant partitions before being applied to probe-side
scans.
+ //
+ // Process:
+ // 1. Store this partition's bounds in the shared accumulator
+ // 2. Atomically increment the completion counter
+ // 3. If we're the last partition to complete, merge all bounds and
update the filter
+ //
+ // Note: In CollectLeft mode, multiple partitions may access the SAME
build data
+ // (shared via OnceFut), but each partition must report separately to
ensure proper
+ // coordination across all output partitions.
+ //
+ // The consequences of not doing this synchronization properly would
be that a filter
+ // with incomplete bounds would be pushed down resulting in incorrect
results (missing rows).
+ if let Some(dynamic_filter) = &self.dynamic_filter {
+ // Store bounds in the accumulator - this runs once per partition
+ if let Some(bounds) = &left_data.bounds {
+ // Only push actual bounds if they exist
+ self.bounds_accumulator.bounds.lock().push(bounds.clone());
+ }
+
+ // Atomically increment the completion counter
+ // Even empty partitions must report to ensure proper termination
+ let completed = self
+ .bounds_accumulator
+ .completed_partitions
+ .fetch_add(1, Ordering::SeqCst)
+ + 1;
+ let total_partitions = self.bounds_accumulator.total_partitions;
+
+ // Critical synchronization point: Only the last partition updates
the filter
+ // Troubleshooting: If you see "completed > total_partitions",
check partition
+ // count calculation in try_new() - it may not match actual
execution calls
+ if completed == total_partitions {
+ if let Some(merged_bounds) =
self.bounds_accumulator.merge_bounds() {
+ let filter_expr =
self.create_filter_from_bounds(merged_bounds)?;
+ dynamic_filter.update(filter_expr)?;
+ }
+ }
Review Comment:
`reset_state` is already implemented for `HashJoinExec` and it does reset
`HashJoinExec::bounds_accumulator`. This bit of code we are commenting on is
within `HashJoinStream` which _is_ created inside of `HashJoinExec::execute`
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