[GitHub] [arrow-datafusion] mingmwang commented on a diff in pull request #5290: TopDown EnforceSorting implementation

["mingmwang (via GitHub)" <gi...@apache.org>]

mingmwang commented on code in PR #5290:
URL: https://github.com/apache/arrow-datafusion/pull/5290#discussion_r1114074800


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datafusion/core/src/physical_optimizer/sort_enforcement2.rs:
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@@ -0,0 +1,2872 @@
+// 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.
+
+//! EnforceSorting optimizer rule inspects the physical plan with respect
+//! to local sorting requirements and does the following:
+//! - Adds a [SortExec] when a requirement is not met,
+//! - Removes an already-existing [SortExec] if it is possible to prove
+//!   that this sort is unnecessary
+//! The rule can work on valid *and* invalid physical plans with respect to
+//! sorting requirements, but always produces a valid physical plan in this sense.
+//!
+//! A non-realistic but easy to follow example for sort removals: Assume that we
+//! somehow get the fragment
+//!
+//! ```text
+//! SortExec: expr=[nullable_col@0 ASC]
+//!   SortExec: expr=[non_nullable_col@1 ASC]
+//! ```
+//!
+//! in the physical plan. The child sort is unnecessary since its result is overwritten
+//! by the parent SortExec. Therefore, this rule removes it from the physical plan.
+use crate::config::ConfigOptions;
+use crate::error::Result;
+use crate::execution::context::TaskContext;
+use crate::physical_optimizer::utils::add_sort_above;
+use crate::physical_optimizer::PhysicalOptimizerRule;
+use crate::physical_plan::coalesce_partitions::CoalescePartitionsExec;
+use crate::physical_plan::filter::FilterExec;
+use crate::physical_plan::joins::utils::JoinSide;
+use crate::physical_plan::joins::SortMergeJoinExec;
+use crate::physical_plan::limit::{GlobalLimitExec, LocalLimitExec};
+use crate::physical_plan::projection::ProjectionExec;
+use crate::physical_plan::repartition::RepartitionExec;
+use crate::physical_plan::rewrite::TreeNodeRewritable;
+use crate::physical_plan::sorts::sort::SortExec;
+use crate::physical_plan::sorts::sort_preserving_merge::SortPreservingMergeExec;
+use crate::physical_plan::union::UnionExec;
+use crate::physical_plan::windows::{BoundedWindowAggExec, WindowAggExec};
+use crate::physical_plan::{
+    with_new_children_if_necessary, DisplayFormatType, Distribution, ExecutionPlan,
+    Partitioning, SendableRecordBatchStream,
+};
+use arrow::datatypes::SchemaRef;
+use datafusion_common::{reverse_sort_options, DataFusionError, Statistics};
+use datafusion_expr::JoinType;
+use datafusion_physical_expr::expressions::Column;
+use datafusion_physical_expr::utils::{
+    create_sort_expr_from_requirement, map_requirement_before_projection,
+    ordering_satisfy, ordering_satisfy_requirement, requirements_compatible,
+};
+use datafusion_physical_expr::window::WindowExpr;
+use datafusion_physical_expr::{
+    new_sort_requirements, EquivalenceProperties, PhysicalExpr, PhysicalSortExpr,
+    PhysicalSortRequirements,
+};
+use itertools::izip;
+use std::any::Any;
+use std::ops::Deref;
+use std::sync::Arc;
+
+/// This rule implements a Top-Down approach to inspects SortExec's in the given physical plan and removes the
+/// ones it can prove unnecessary.
+#[derive(Default)]
+pub struct TopDownEnforceSorting {}
+
+impl TopDownEnforceSorting {
+    #[allow(missing_docs)]
+    pub fn new() -> Self {
+        Self {}
+    }
+}
+
+/// This is a "data class" we use within the [TopDownEnforceSorting] rule
+#[derive(Debug, Clone)]
+struct PlanWithSortRequirements {
+    /// Current plan
+    plan: Arc<dyn ExecutionPlan>,
+    /// Whether the plan could impact the final result ordering
+    impact_result_ordering: bool,
+    /// Parent has the SinglePartition requirement to children
+    satisfy_single_distribution: bool,
+    /// Parent required sort ordering
+    required_ordering: Option<Vec<PhysicalSortRequirements>>,
+    /// The adjusted request sort ordering to children.
+    /// By default they are the same as the plan's required input ordering, but can be adjusted based on parent required sort ordering properties.
+    adjusted_request_ordering: Vec<Option<Vec<PhysicalSortRequirements>>>,
+}
+
+impl PlanWithSortRequirements {
+    pub fn init(plan: Arc<dyn ExecutionPlan>) -> Self {
+        let impact_result_ordering = plan.output_ordering().is_some()
+            || plan.output_partitioning().partition_count() <= 1
+            || plan.as_any().downcast_ref::<GlobalLimitExec>().is_some()
+            || plan.as_any().downcast_ref::<LocalLimitExec>().is_some();

Review Comment:
   Sure, will do.



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