Unnecessary SortExec removal rule from Physical Plan

datafusion/common/src/lib.rs

@@ -30,6 +30,7 @@ pub mod stats;
 mod table_reference;
 pub mod test_util;
 
+use arrow::compute::SortOptions;
 pub use column::Column;
 pub use dfschema::{DFField, DFSchema, DFSchemaRef, ExprSchema, ToDFSchema};
 pub use error::{field_not_found, DataFusionError, Result, SchemaError};
@@ -63,3 +64,12 @@ macro_rules! downcast_value {
         })?
     }};
 }
+
+/// Computes the "reverse" of given `SortOptions`.
+// TODO: If/when arrow supports `!` for `SortOptions`, we can remove this.
+pub fn reverse_sort_options(options: SortOptions) -> SortOptions {
+    SortOptions {
+        descending: !options.descending,
+        nulls_first: !options.nulls_first,
+    }
+}

datafusion/core/src/execution/context.rs

@@ -100,6 +100,7 @@ use url::Url;
 use crate::catalog::listing_schema::ListingSchemaProvider;
 use crate::datasource::object_store::ObjectStoreUrl;
 use crate::execution::memory_pool::MemoryPool;
+use crate::physical_optimizer::optimize_sorts::OptimizeSorts;
 use uuid::Uuid;
 
 use super::options::{
@@ -1580,6 +1581,12 @@ impl SessionState {
         // To make sure the SinglePartition is satisfied, run the BasicEnforcement again, originally it was the AddCoalescePartitionsExec here.
         physical_optimizers.push(Arc::new(BasicEnforcement::new()));
 
+        // `BasicEnforcement` stage conservatively inserts `SortExec`s to satisfy ordering requirements.
+        // However, a deeper analysis may sometimes reveal that such a `SortExec` is actually unnecessary.
+        // These cases typically arise when we have reversible `WindowAggExec`s or deep subqueries. The
+        // rule below performs this analysis and removes unnecessary `SortExec`s.
+        physical_optimizers.push(Arc::new(OptimizeSorts::new()));
+
         let mut this = SessionState {
             session_id,
             optimizer: Optimizer::new(),

datafusion/core/src/physical_optimizer/enforcement.rs

@@ -20,6 +20,7 @@
 //!
 use crate::config::OPT_TOP_DOWN_JOIN_KEY_REORDERING;
 use crate::error::Result;
+use crate::physical_optimizer::utils::{add_sort_above_child, ordering_satisfy};
 use crate::physical_optimizer::PhysicalOptimizerRule;
 use crate::physical_plan::aggregates::{AggregateExec, AggregateMode, PhysicalGroupBy};
 use crate::physical_plan::coalesce_partitions::CoalescePartitionsExec;
@@ -29,8 +30,7 @@ use crate::physical_plan::joins::{
 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::SortOptions;
+use crate::physical_plan::sorts::sort::{SortExec, SortOptions};
 use crate::physical_plan::sorts::sort_preserving_merge::SortPreservingMergeExec;
 use crate::physical_plan::windows::WindowAggExec;
 use crate::physical_plan::Partitioning;
@@ -42,9 +42,8 @@ use datafusion_physical_expr::equivalence::EquivalenceProperties;
 use datafusion_physical_expr::expressions::Column;
 use datafusion_physical_expr::expressions::NoOp;
 use datafusion_physical_expr::{
-    expr_list_eq_strict_order, normalize_expr_with_equivalence_properties,
-    normalize_sort_expr_with_equivalence_properties, AggregateExpr, PhysicalExpr,
-    PhysicalSortExpr,
+    expr_list_eq_strict_order, normalize_expr_with_equivalence_properties, AggregateExpr,
+    PhysicalExpr,
 };
 use std::collections::HashMap;
 use std::sync::Arc;
@@ -919,71 +918,14 @@ fn ensure_distribution_and_ordering(
                 Ok(child)
             } else {
                 let sort_expr = required.unwrap().to_vec();
-                Ok(Arc::new(SortExec::new_with_partitioning(
-                    sort_expr, child, true, None,
-                )) as Arc<dyn ExecutionPlan>)
+                add_sort_above_child(&child, sort_expr)
             }
         })
         .collect();
 
     with_new_children_if_necessary(plan, new_children?)
 }
 
-/// Check the required ordering requirements are satisfied by the provided PhysicalSortExprs.
-fn ordering_satisfy<F: FnOnce() -> EquivalenceProperties>(
-    provided: Option<&[PhysicalSortExpr]>,
-    required: Option<&[PhysicalSortExpr]>,
-    equal_properties: F,
-) -> bool {
-    match (provided, required) {
-        (_, None) => true,
-        (None, Some(_)) => false,
-        (Some(provided), Some(required)) => {
-            if required.len() > provided.len() {
-                false
-            } else {
-                let fast_match = required
-                    .iter()
-                    .zip(provided.iter())
-                    .all(|(order1, order2)| order1.eq(order2));
-
-                if !fast_match {
-                    let eq_properties = equal_properties();
-                    let eq_classes = eq_properties.classes();
-                    if !eq_classes.is_empty() {
-                        let normalized_required_exprs = required
-                            .iter()
-                            .map(|e| {
-                                normalize_sort_expr_with_equivalence_properties(
-                                    e.clone(),
-                                    eq_classes,
-                                )
-                            })
-                            .collect::<Vec<_>>();
-                        let normalized_provided_exprs = provided
-                            .iter()
-                            .map(|e| {
-                                normalize_sort_expr_with_equivalence_properties(
-                                    e.clone(),
-                                    eq_classes,
-                                )
-                            })
-                            .collect::<Vec<_>>();
-                        normalized_required_exprs
-                            .iter()
-                            .zip(normalized_provided_exprs.iter())
-                            .all(|(order1, order2)| order1.eq(order2))
-                    } else {
-                        fast_match
-                    }
-                } else {
-                    fast_match
-                }
-            }
-        }
-    }
-}
-
 #[derive(Debug, Clone)]
 struct JoinKeyPairs {
     left_keys: Vec<Arc<dyn PhysicalExpr>>,
@@ -1063,10 +1005,10 @@ mod tests {
     use arrow::datatypes::{DataType, Field, Schema, SchemaRef};
     use datafusion_expr::logical_plan::JoinType;
     use datafusion_expr::Operator;
-    use datafusion_physical_expr::expressions::binary;
-    use datafusion_physical_expr::expressions::lit;
-    use datafusion_physical_expr::expressions::Column;
-    use datafusion_physical_expr::{expressions, PhysicalExpr};
+    use datafusion_physical_expr::{
+        expressions, expressions::binary, expressions::lit, expressions::Column,
+        PhysicalExpr, PhysicalSortExpr,
+    };
     use std::ops::Deref;
 
     use super::*;

datafusion/core/src/physical_optimizer/mod.rs

@@ -22,6 +22,7 @@ pub mod aggregate_statistics;
 pub mod coalesce_batches;
 pub mod enforcement;
 pub mod join_selection;
+pub mod optimize_sorts;
 pub mod optimizer;
 pub mod pruning;
 pub mod repartition;