feat: support input reordering for NestedLoopJoinExec (apache#9676)

* support input reordering for NestedLoopJoinExec

* renamed variables and struct fields

* fixed nl join filter expression in tests

* Update datafusion/physical-plan/src/joins/nested_loop_join.rs

Co-authored-by: Andrew Lamb <[email protected]>

* typo fixed

---------

Co-authored-by: Andrew Lamb <[email protected]>

Author: 2 people

datafusion/core/src/physical_optimizer/join_selection.rs

@@ -30,8 +30,8 @@ use crate::error::Result;
 use crate::physical_optimizer::PhysicalOptimizerRule;
 use crate::physical_plan::joins::utils::{ColumnIndex, JoinFilter};
 use crate::physical_plan::joins::{
-    CrossJoinExec, HashJoinExec, PartitionMode, StreamJoinPartitionMode,
-    SymmetricHashJoinExec,
+    CrossJoinExec, HashJoinExec, NestedLoopJoinExec, PartitionMode,
+    StreamJoinPartitionMode, SymmetricHashJoinExec,
 };
 use crate::physical_plan::projection::ProjectionExec;
 use crate::physical_plan::{ExecutionPlan, ExecutionPlanProperties};
@@ -199,6 +199,38 @@ fn swap_hash_join(
     }
 }
 
+/// Swaps inputs of `NestedLoopJoinExec` and wraps it into `ProjectionExec` is required
+fn swap_nl_join(join: &NestedLoopJoinExec) -> Result<Arc<dyn ExecutionPlan>> {
+    let new_filter = swap_join_filter(join.filter());
+    let new_join_type = &swap_join_type(*join.join_type());
+
+    let new_join = NestedLoopJoinExec::try_new(
+        Arc::clone(join.right()),
+        Arc::clone(join.left()),
+        new_filter,
+        new_join_type,
+    )?;
+
+    // For Semi/Anti joins, swap result will produce same output schema,
+    // no need to wrap them into additional projection
+    let plan: Arc<dyn ExecutionPlan> = if matches!(
+        join.join_type(),
+        JoinType::LeftSemi
+            | JoinType::RightSemi
+            | JoinType::LeftAnti
+            | JoinType::RightAnti
+    ) {
+        Arc::new(new_join)
+    } else {
+        let projection =
+            swap_reverting_projection(&join.left().schema(), &join.right().schema());
+
+        Arc::new(ProjectionExec::try_new(projection, Arc::new(new_join))?)
+    };
+
+    Ok(plan)
+}
+
 /// When the order of the join is changed by the optimizer, the columns in
 /// the output should not be impacted. This function creates the expressions
 /// that will allow to swap back the values from the original left as the first
@@ -438,6 +470,14 @@ fn statistical_join_selection_subrule(
             } else {
                 None
             }
+        } else if let Some(nl_join) = plan.as_any().downcast_ref::<NestedLoopJoinExec>() {
+            let left = nl_join.left();
+            let right = nl_join.right();
+            if should_swap_join_order(&**left, &**right)? {
+                swap_nl_join(nl_join).map(Some)?
+            } else {
+                None
+            }
         } else {
             None
         };
@@ -674,9 +714,12 @@ mod tests_statistical {
 
     use arrow::datatypes::{DataType, Field, Schema};
     use datafusion_common::{stats::Precision, JoinType, ScalarValue};
-    use datafusion_physical_expr::expressions::Column;
+    use datafusion_expr::Operator;
+    use datafusion_physical_expr::expressions::{BinaryExpr, Column};
     use datafusion_physical_expr::{PhysicalExpr, PhysicalExprRef};
 
+    use rstest::rstest;
+
     /// Return statistcs for empty table
     fn empty_statistics() -> Statistics {
         Statistics {
@@ -762,6 +805,35 @@ mod tests_statistical {
         }]
     }
 
+    /// Create join filter for NLJoinExec with expression `big_col > small_col`
+    /// where both columns are 0-indexed and come from left and right inputs respectively
+    fn nl_join_filter() -> Option<JoinFilter> {
+        let column_indices = vec![
+            ColumnIndex {
+                index: 0,
+                side: JoinSide::Left,
+            },
+            ColumnIndex {
+                index: 0,
+                side: JoinSide::Right,
+            },
+        ];
+        let intermediate_schema = Schema::new(vec![
+            Field::new("big_col", DataType::Int32, false),
+            Field::new("small_col", DataType::Int32, false),
+        ]);
+        let expression = Arc::new(BinaryExpr::new(
+            Arc::new(Column::new_with_schema("big_col", &intermediate_schema).unwrap()),
+            Operator::Gt,
+            Arc::new(Column::new_with_schema("small_col", &intermediate_schema).unwrap()),
+        )) as _;
+        Some(JoinFilter::new(
+            expression,
+            column_indices,
+            intermediate_schema,
+        ))
+    }
+
     /// Returns three plans with statistics of (min, max, distinct_count)
     /// * big 100K rows @ (0, 50k, 50k)
     /// * medium 10K rows @ (1k, 5k, 1k)
@@ -1114,6 +1186,137 @@ mod tests_statistical {
         crosscheck_plans(join).unwrap();
     }
 
+    #[rstest(
+        join_type,
+        case::inner(JoinType::Inner),
+        case::left(JoinType::Left),
+        case::right(JoinType::Right),
+        case::full(JoinType::Full)
+    )]
+    #[tokio::test]
+    async fn test_nl_join_with_swap(join_type: JoinType) {
+        let (big, small) = create_big_and_small();
+
+        let join = Arc::new(
+            NestedLoopJoinExec::try_new(
+                Arc::clone(&big),
+                Arc::clone(&small),
+                nl_join_filter(),
+                &join_type,
+            )
+            .unwrap(),
+        );
+
+        let optimized_join = JoinSelection::new()
+            .optimize(join.clone(), &ConfigOptions::new())
+            .unwrap();
+
+        let swapping_projection = optimized_join
+            .as_any()
+            .downcast_ref::<ProjectionExec>()
+            .expect("A proj is required to swap columns back to their original order");
+
+        assert_eq!(swapping_projection.expr().len(), 2);
+        let (col, name) = &swapping_projection.expr()[0];
+        assert_eq!(name, "big_col");
+        assert_col_expr(col, "big_col", 1);
+        let (col, name) = &swapping_projection.expr()[1];
+        assert_eq!(name, "small_col");
+        assert_col_expr(col, "small_col", 0);
+
+        let swapped_join = swapping_projection
+            .input()
+            .as_any()
+            .downcast_ref::<NestedLoopJoinExec>()
+            .expect("The type of the plan should not be changed");
+
+        // Assert join side of big_col swapped in filter expression
+        let swapped_filter = swapped_join.filter().unwrap();
+        let swapped_big_col_idx = swapped_filter.schema().index_of("big_col").unwrap();
+        let swapped_big_col_side = swapped_filter
+            .column_indices()
+            .get(swapped_big_col_idx)
+            .unwrap()
+            .side;
+        assert_eq!(
+            swapped_big_col_side,
+            JoinSide::Right,
+            "Filter column side should be swapped"
+        );
+
+        assert_eq!(
+            swapped_join.left().statistics().unwrap().total_byte_size,
+            Precision::Inexact(8192)
+        );
+        assert_eq!(
+            swapped_join.right().statistics().unwrap().total_byte_size,
+            Precision::Inexact(2097152)
+        );
+        crosscheck_plans(join.clone()).unwrap();
+    }
+
+    #[rstest(
+        join_type,
+        case::left_semi(JoinType::LeftSemi),
+        case::left_anti(JoinType::LeftAnti),
+        case::right_semi(JoinType::RightSemi),
+        case::right_anti(JoinType::RightAnti)
+    )]
+    #[tokio::test]
+    async fn test_nl_join_with_swap_no_proj(join_type: JoinType) {
+        let (big, small) = create_big_and_small();
+
+        let join = Arc::new(
+            NestedLoopJoinExec::try_new(
+                Arc::clone(&big),
+                Arc::clone(&small),
+                nl_join_filter(),
+                &join_type,
+            )
+            .unwrap(),
+        );
+
+        let optimized_join = JoinSelection::new()
+            .optimize(join.clone(), &ConfigOptions::new())
+            .unwrap();
+
+        let swapped_join = optimized_join
+            .as_any()
+            .downcast_ref::<NestedLoopJoinExec>()
+            .expect("The type of the plan should not be changed");
+
+        // Assert before/after schemas are equal
+        assert_eq!(
+            join.schema(),
+            swapped_join.schema(),
+            "Join schema should not be modified while optimization"
+        );
+
+        // Assert join side of big_col swapped in filter expression
+        let swapped_filter = swapped_join.filter().unwrap();
+        let swapped_big_col_idx = swapped_filter.schema().index_of("big_col").unwrap();
+        let swapped_big_col_side = swapped_filter
+            .column_indices()
+            .get(swapped_big_col_idx)
+            .unwrap()
+            .side;
+        assert_eq!(
+            swapped_big_col_side,
+            JoinSide::Right,
+            "Filter column side should be swapped"
+        );
+
+        assert_eq!(
+            swapped_join.left().statistics().unwrap().total_byte_size,
+            Precision::Inexact(8192)
+        );
+        assert_eq!(
+            swapped_join.right().statistics().unwrap().total_byte_size,
+            Precision::Inexact(2097152)
+        );
+        crosscheck_plans(join.clone()).unwrap();
+    }
+
     #[tokio::test]
     async fn test_swap_reverting_projection() {
         let left_schema = Schema::new(vec![

datafusion/core/tests/fuzz_cases/join_fuzz.rs

@@ -21,13 +21,19 @@ use arrow::array::{ArrayRef, Int32Array};
 use arrow::compute::SortOptions;
 use arrow::record_batch::RecordBatch;
 use arrow::util::pretty::pretty_format_batches;
+use arrow_schema::Schema;
 use rand::Rng;
 
+use datafusion::common::JoinSide;
+use datafusion::logical_expr::{JoinType, Operator};
+use datafusion::physical_expr::expressions::BinaryExpr;
 use datafusion::physical_plan::collect;
 use datafusion::physical_plan::expressions::Column;
-use datafusion::physical_plan::joins::{HashJoinExec, PartitionMode, SortMergeJoinExec};
+use datafusion::physical_plan::joins::utils::{ColumnIndex, JoinFilter};
+use datafusion::physical_plan::joins::{
+    HashJoinExec, NestedLoopJoinExec, PartitionMode, SortMergeJoinExec,
+};
 use datafusion::physical_plan::memory::MemoryExec;
-use datafusion_expr::JoinType;
 
 use datafusion::prelude::{SessionConfig, SessionContext};
 use test_utils::stagger_batch_with_seed;
@@ -73,7 +79,7 @@ async fn test_full_join_1k() {
 }
 
 #[tokio::test]
-async fn test_semi_join_1k() {
+async fn test_semi_join_10k() {
     run_join_test(
         make_staggered_batches(10000),
         make_staggered_batches(10000),
@@ -83,7 +89,7 @@ async fn test_semi_join_1k() {
 }
 
 #[tokio::test]
-async fn test_anti_join_1k() {
+async fn test_anti_join_10k() {
     run_join_test(
         make_staggered_batches(10000),
         make_staggered_batches(10000),
@@ -118,6 +124,46 @@ async fn run_join_test(
             ),
         ];
 
+        // Nested loop join uses filter for joining records
+        let column_indices = vec![
+            ColumnIndex {
+                index: 0,
+                side: JoinSide::Left,
+            },
+            ColumnIndex {
+                index: 1,
+                side: JoinSide::Left,
+            },
+            ColumnIndex {
+                index: 0,
+                side: JoinSide::Right,
+            },
+            ColumnIndex {
+                index: 1,
+                side: JoinSide::Right,
+            },
+        ];
+        let intermediate_schema = Schema::new(vec![
+            schema1.field_with_name("a").unwrap().to_owned(),
+            schema1.field_with_name("b").unwrap().to_owned(),
+            schema2.field_with_name("a").unwrap().to_owned(),
+            schema2.field_with_name("b").unwrap().to_owned(),
+        ]);
+
+        let equal_a = Arc::new(BinaryExpr::new(
+            Arc::new(Column::new("a", 0)),
+            Operator::Eq,
+            Arc::new(Column::new("a", 2)),
+        )) as _;
+        let equal_b = Arc::new(BinaryExpr::new(
+            Arc::new(Column::new("b", 1)),
+            Operator::Eq,
+            Arc::new(Column::new("b", 3)),
+        )) as _;
+        let expression = Arc::new(BinaryExpr::new(equal_a, Operator::And, equal_b)) as _;
+
+        let on_filter = JoinFilter::new(expression, column_indices, intermediate_schema);
+
         // sort-merge join
         let left = Arc::new(
             MemoryExec::try_new(&[input1.clone()], schema1.clone(), None).unwrap(),
@@ -161,22 +207,55 @@ async fn run_join_test(
         );
         let hj_collected = collect(hj, task_ctx.clone()).await.unwrap();
 
+        // nested loop join
+        let left = Arc::new(
+            MemoryExec::try_new(&[input1.clone()], schema1.clone(), None).unwrap(),
+        );
+        let right = Arc::new(
+            MemoryExec::try_new(&[input2.clone()], schema2.clone(), None).unwrap(),
+        );
+        let nlj = Arc::new(
+            NestedLoopJoinExec::try_new(left, right, Some(on_filter), &join_type)
+                .unwrap(),
+        );
+        let nlj_collected = collect(nlj, task_ctx.clone()).await.unwrap();
+
         // compare
         let smj_formatted = pretty_format_batches(&smj_collected).unwrap().to_string();
         let hj_formatted = pretty_format_batches(&hj_collected).unwrap().to_string();
+        let nlj_formatted = pretty_format_batches(&nlj_collected).unwrap().to_string();
 
         let mut smj_formatted_sorted: Vec<&str> = smj_formatted.trim().lines().collect();
         smj_formatted_sorted.sort_unstable();
 
         let mut hj_formatted_sorted: Vec<&str> = hj_formatted.trim().lines().collect();
         hj_formatted_sorted.sort_unstable();
 
+        let mut nlj_formatted_sorted: Vec<&str> = nlj_formatted.trim().lines().collect();
+        nlj_formatted_sorted.sort_unstable();
+
         for (i, (smj_line, hj_line)) in smj_formatted_sorted
             .iter()
             .zip(&hj_formatted_sorted)
             .enumerate()
         {
-            assert_eq!((i, smj_line), (i, hj_line));
+            assert_eq!(
+                (i, smj_line),
+                (i, hj_line),
+                "SortMergeJoinExec and HashJoinExec produced different results"
+            );
+        }
+
+        for (i, (nlj_line, hj_line)) in nlj_formatted_sorted
+            .iter()
+            .zip(&hj_formatted_sorted)
+            .enumerate()
+        {
+            assert_eq!(
+                (i, nlj_line),
+                (i, hj_line),
+                "NestedLoopJoinExec and HashJoinExec produced different results"
+            );
         }
     }
 }