alamb commented on code in PR #21815: URL: https://github.com/apache/datafusion/pull/21815#discussion_r3375696120
########## datafusion/physical-plan/src/statistics.rs: ########## @@ -0,0 +1,168 @@ +// 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. + +//! Statistics computation for physical plans. +//! +//! [`StatisticsArgs`] provides external context to +//! [`ExecutionPlan::statistics_with_args`]. + +use crate::ExecutionPlan; +use datafusion_common::{Result, Statistics, assert_or_internal_err}; +use std::cell::RefCell; +use std::collections::HashMap; +use std::rc::Rc; +use std::sync::Arc; + +/// Per-call memoization cache for statistics computation. +/// +/// Keyed by `(plan node pointer address, partition)`. Shared across +/// a single statistics walk via [`StatisticsArgs`]. +/// +/// The pointer-based key is safe within a single synchronous walk: +/// 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 statistics walk. + cache: Rc<RefCell<StatsCache>>, +} + +impl StatisticsArgs { + /// Creates new statistics arguments with a fresh cache. + pub fn new(partition: Option<usize>) -> Self { Review Comment: I think we can make this API a little easier to use / more ergonomic -- here is a proposal for your consideration: - https://github.com/asolimando/datafusion/pull/1 By making partition optional I think it makes the callsites that do set it clearer and will make it easier to extend this structure going forward. ########## datafusion/ffi/src/execution_plan.rs: ########## @@ -209,6 +209,7 @@ unsafe extern "C" fn partition_statistics_fn_wrapper( partition: FFI_Option<usize>, ) -> FFI_Result<SVec<u8>> { let partition: Option<usize> = partition.into(); + #[expect(deprecated)] Review Comment: Claude caught that this call would be dangerous for people who had correctly updated their plans: it would still call the old `partition_statistics` implementation - https://github.com/asolimando/datafusion/pull/2 ########## 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: I guess I was thinking we could make it ```rust fn statistics_with_args(&self, args: &StatisticsArgs) -> Result<Arc<Statistics>> { if let Some(idx) = args.partition() { // Validate partition index let partition_count = self.properties().partitioning.partition_count(); assert_or_internal_err!( idx < partition_count, "Invalid partition index: {}, the partition count is {}", idx, partition_count ); } Ok(Arc::new(Statistics::new_unknown(&self.schema()))) } ``` (aka literally copy/paste the implementation of partition_statistics inline) -- This is an automated message from the Apache Git Service. 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