xudong963 commented on code in PR #21815:
URL: https://github.com/apache/datafusion/pull/21815#discussion_r3286236478
##########
datafusion/physical-plan/src/execution_plan.rs:
##########
@@ -563,6 +566,22 @@ pub trait ExecutionPlan: Any + Debug + DisplayAs + Send +
Sync {
Ok(Arc::new(Statistics::new_unknown(&self.schema())))
}
+ /// Returns statistics for a specific partition of this `ExecutionPlan`
node.
+ /// If statistics are not available, should return
[`Statistics::new_unknown`]
+ /// (the default), not an error.
+ /// If `partition` is `None`, it returns statistics for the entire plan.
+ ///
+ /// [`StatisticsArgs`] carries the partition index, pre-computed child
+ /// statistics, and a shared cache. See [`compute_statistics`] for the
+ /// top-level entry point that builds the args automatically.
+ ///
+ /// [`StatisticsArgs`]: crate::statistics_context::StatisticsArgs
+ /// [`compute_statistics`]: crate::statistics_context::compute_statistics
+ fn statistics_with_args(&self, args: &StatisticsArgs) ->
Result<Arc<Statistics>> {
+ #[expect(deprecated)]
+ self.partition_statistics(args.partition())
Review Comment:
after the method is deprecated, we need to update the method again, how
about making it not rely on the partition_statistics method
##########
datafusion/physical-plan/src/statistics_context.rs:
##########
@@ -0,0 +1,213 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! Context for computing statistics in physical plans.
+//!
+//! [`StatisticsArgs`] provides external context to
+//! [`ExecutionPlan::statistics_with_args`], enabling operators to look up
+//! pre-computed child statistics via a shared cache.
+
+use crate::ExecutionPlan;
+use datafusion_common::Result;
+use datafusion_common::Statistics;
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::rc::Rc;
+use std::sync::Arc;
+
+/// Per-call memoization cache for [`compute_statistics`].
+///
+/// Keyed by `(plan node pointer address, partition)`. Created once per
+/// top-level [`compute_statistics`] call and shared across all recursive
+/// and operator-internal calls via [`StatisticsArgs`].
+///
+/// The pointer-based key is safe within a single synchronous
+/// `compute_statistics` call: all `Arc<dyn ExecutionPlan>` nodes are held
+/// by the plan tree for the duration of the walk, so addresses cannot be
+/// reused.
+#[derive(Debug, Default)]
+struct StatsCache(HashMap<(usize, Option<usize>), Arc<Statistics>>);
+
+impl StatsCache {
+ fn get(
+ &self,
+ plan: &dyn ExecutionPlan,
+ partition: Option<usize>,
+ ) -> Option<&Arc<Statistics>> {
+ let key = (
+ plan as *const dyn ExecutionPlan as *const () as usize,
+ partition,
+ );
+ self.0.get(&key)
+ }
+
+ fn insert(
+ &mut self,
+ plan: &dyn ExecutionPlan,
+ partition: Option<usize>,
+ stats: Arc<Statistics>,
+ ) {
+ let key = (
+ plan as *const dyn ExecutionPlan as *const () as usize,
+ partition,
+ );
+ self.0.insert(key, stats);
+ }
+}
+
+/// Arguments passed to [`ExecutionPlan::statistics_with_args`] carrying
+/// external information that operators can use when computing their
+/// statistics.
+#[derive(Debug)]
+pub struct StatisticsArgs {
+ partition: Option<usize>,
+ /// Shared memoization cache for the current `compute_statistics` walk.
+ /// Children's overall (`None`) stats are pre-populated by
+ /// `compute_statistics_inner` before calling the operator.
+ cache: Option<Rc<RefCell<StatsCache>>>,
+}
+
+impl StatisticsArgs {
+ /// Creates new statistics arguments without a shared cache.
+ /// Used by callers outside of `compute_statistics` (e.g. benchmarks).
+ pub fn new(partition: Option<usize>) -> Self {
+ Self {
+ partition,
+ cache: None,
+ }
+ }
+
+ pub fn partition(&self) -> Option<usize> {
+ self.partition
+ }
+
+ /// Returns the pre-computed overall (`None`) statistics for a child.
+ /// For per-partition stats, use [`Self::child_stats_for`].
+ pub fn child_stats_of(&self, child: &dyn ExecutionPlan) ->
Result<Arc<Statistics>> {
+ self.compute_child_statistics(child, None)
+ }
+
+ /// Returns statistics for a child, using pre-computed overall stats
+ /// when `partition` is `None`, or computing per-partition stats on
+ /// demand when `partition` is `Some`.
+ pub fn child_stats_for(&self, child: &dyn ExecutionPlan) ->
Result<Arc<Statistics>> {
+ self.compute_child_statistics(child, self.partition)
+ }
+
+ /// Computes statistics for a child plan, using the shared cache
+ /// from the current [`compute_statistics`] walk.
+ pub fn compute_child_statistics(
+ &self,
+ plan: &dyn ExecutionPlan,
+ partition: Option<usize>,
+ ) -> Result<Arc<Statistics>> {
+ match &self.cache {
+ Some(cache) => compute_statistics_inner(plan, partition, cache),
+ None => compute_statistics(plan, partition),
+ }
+ }
+}
+
+/// Computes statistics for a plan node by first recursively computing
+/// overall (`None`) statistics for all children, then calling
+/// [`ExecutionPlan::statistics_with_args`].
+///
+/// Results are memoized within a single call: operators that call
+/// [`StatisticsArgs::child_stats_of`] or [`StatisticsArgs::child_stats_for`]
+/// will hit the cache instead of re-walking subtrees.
+///
+/// Children are always pre-computed with `partition = None` (overall stats).
+/// Operators that need per-partition child stats (e.g., partition-preserving
+/// operators when called with `Some(partition)`) should use
+/// [`StatisticsArgs::child_stats_for`].
+pub fn compute_statistics(
+ plan: &dyn ExecutionPlan,
+ partition: Option<usize>,
+) -> Result<Arc<Statistics>> {
+ let cache = Rc::new(RefCell::new(StatsCache::default()));
+ compute_statistics_inner(plan, partition, &cache)
+}
+
+fn compute_statistics_inner(
+ plan: &dyn ExecutionPlan,
+ partition: Option<usize>,
+ cache: &Rc<RefCell<StatsCache>>,
+) -> Result<Arc<Statistics>> {
+ if let Some(cached) = cache.borrow().get(plan, partition) {
+ return Ok(Arc::clone(cached));
+ }
+
+ for child in plan.children() {
+ compute_statistics_inner(child.as_ref(), None, cache)?;
Review Comment:
here, always computes every child with `partition = None` before calling
the current node.
##########
datafusion/physical-plan/src/coalesce_batches.rs:
##########
@@ -344,8 +344,6 @@ impl CoalesceBatchesStream {
None => {
// Input stream is exhausted, finalize any remaining
batches
self.completed = true;
- self.input =
-
Box::pin(EmptyRecordBatchStream::new(self.coalescer.schema()));
Review Comment:
why removed here?
##########
datafusion/physical-plan/src/coalesce_batches.rs:
##########
@@ -356,9 +354,6 @@ impl CoalesceBatchesStream {
PushBatchStatus::LimitReached => {
// limit was reached, so stop early
self.completed = true;
- self.input = Box::pin(EmptyRecordBatchStream::new(
- self.coalescer.schema(),
- ));
Review Comment:
ditto
##########
datafusion-examples/examples/relation_planner/table_sample.rs:
##########
@@ -722,8 +722,8 @@ impl ExecutionPlan for SampleExec {
Some(self.metrics.clone_inner())
}
- fn partition_statistics(&self, partition: Option<usize>) ->
Result<Arc<Statistics>> {
- let mut stats =
Arc::unwrap_or_clone(self.input.partition_statistics(partition)?);
+ fn statistics_with_args(&self, args: &StatisticsArgs) ->
Result<Arc<Statistics>> {
+ let mut stats =
Arc::unwrap_or_clone(args.child_stats_of(self.input.as_ref())?);
Review Comment:
it uses `child_stats_of`, but `SampleExec::execute` reads the same input
partition and preserves partitioning.
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