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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2022/06/19 12:36:41 UTC
[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #2740: Add optimizer rule to filter out null keys before a join
alamb commented on code in PR #2740:
URL: https://github.com/apache/arrow-datafusion/pull/2740#discussion_r901100179
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datafusion/optimizer/src/filter_null_join_keys.rs:
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@@ -0,0 +1,247 @@
+// 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.
+
+//! The FilterNullJoinKeys rule will identify inner joins with equi-join conditions
+//! where the join key is nullable on one side and non-nullable on the other side
+//! and then insert an `IsNotNull` filter on the nullable side since null values
+//! can never match.
+
+use crate::{utils, OptimizerConfig, OptimizerRule};
+use datafusion_common::{Column, DFField, DFSchemaRef};
+use datafusion_expr::{
+ and, logical_plan::Filter, logical_plan::JoinType, Expr, LogicalPlan,
+};
+use std::sync::Arc;
+
+/// The FilterNullJoinKeys rule will identify inner joins with equi-join conditions
+/// where the join key is nullable on one side and non-nullable on the other side
+/// and then insert an `IsNotNull` filter on the nullable side since null values
+/// can never match.
+#[derive(Default)]
+pub struct FilterNullJoinKeys {}
+
+impl OptimizerRule for FilterNullJoinKeys {
+ fn optimize(
+ &self,
+ plan: &LogicalPlan,
+ optimizer_config: &OptimizerConfig,
+ ) -> datafusion_common::Result<LogicalPlan> {
+ match plan {
+ LogicalPlan::Join(join) if join.join_type == JoinType::Inner => {
+ // recurse down first and optimize inputs
+ let mut join = join.clone();
+ join.left = Arc::new(self.optimize(&join.left, optimizer_config)?);
+ join.right = Arc::new(self.optimize(&join.right, optimizer_config)?);
+
+ let left_schema = join.left.schema();
+ let right_schema = join.right.schema();
+
+ let mut left_filters = vec![];
+ let mut right_filters = vec![];
+
+ for (l, r) in &join.on {
+ if let Some((left_field, right_field)) =
+ resolve_join_key_pair(left_schema, right_schema, l, r)
+ {
+ if left_field.is_nullable() && !right_field.is_nullable() {
+ left_filters.push(l.clone());
+ } else if !left_field.is_nullable() && right_field.is_nullable() {
+ right_filters.push(r.clone());
+ }
+ }
+ }
+
+ if !left_filters.is_empty() {
+ let predicate = create_not_null_predicate(left_filters);
+ join.left = Arc::new(LogicalPlan::Filter(Filter {
+ predicate,
+ input: join.left.clone(),
+ }));
+ }
+ if !right_filters.is_empty() {
+ let predicate = create_not_null_predicate(right_filters);
+ join.right = Arc::new(LogicalPlan::Filter(Filter {
+ predicate,
+ input: join.right.clone(),
+ }));
+ }
+ Ok(LogicalPlan::Join(join))
+ }
+ _ => {
+ // Apply the optimization to all inputs of the plan
+ utils::optimize_children(self, plan, optimizer_config)
+ }
+ }
+ }
+
+ fn name(&self) -> &str {
+ "FilterNullJoinKeys"
+ }
+}
+
+fn create_not_null_predicate(columns: Vec<Column>) -> Expr {
+ let not_null_exprs: Vec<Expr> = columns
+ .into_iter()
+ .map(|c| Expr::IsNotNull(Box::new(Expr::Column(c))))
+ .collect();
+ // combine the IsNotNull expressions with AND
+ not_null_exprs
+ .iter()
+ .skip(1)
+ .fold(not_null_exprs[0].clone(), |a, b| and(a, b.clone()))
+}
+
+fn resolve_join_key_pair(
+ left_schema: &DFSchemaRef,
+ right_schema: &DFSchemaRef,
+ c1: &Column,
+ c2: &Column,
+) -> Option<(DFField, DFField)> {
+ resolve_fields(left_schema, right_schema, c1, c2)
+ .or_else(|| resolve_fields(left_schema, right_schema, c2, c1))
+}
+
+fn resolve_fields(
+ left_schema: &DFSchemaRef,
+ right_schema: &DFSchemaRef,
+ c1: &Column,
+ c2: &Column,
+) -> Option<(DFField, DFField)> {
+ match (
+ left_schema.index_of_column(c1),
+ right_schema.index_of_column(c2),
+ ) {
+ (Ok(left_index), Ok(right_index)) => {
+ let left_field = left_schema.field(left_index);
+ let right_field = right_schema.field(right_index);
+ Some((left_field.clone(), right_field.clone()))
+ }
+ _ => None,
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ use arrow::datatypes::{DataType, Field, Schema};
+ use datafusion_common::{Column, Result};
+ use datafusion_expr::logical_plan::table_scan;
+ use datafusion_expr::{logical_plan::JoinType, LogicalPlanBuilder};
+
+ fn optimize_plan(plan: &LogicalPlan) -> LogicalPlan {
+ let rule = FilterNullJoinKeys::default();
+ rule.optimize(plan, &OptimizerConfig::new())
+ .expect("failed to optimize plan")
+ }
+
+ fn assert_optimized_plan_eq(plan: &LogicalPlan, expected: &str) {
+ let optimized_plan = optimize_plan(plan);
+ let formatted_plan = format!("{:?}", optimized_plan);
+ assert_eq!(formatted_plan, expected);
+ }
+
+ #[test]
+ fn left_nullable() -> Result<()> {
Review Comment:
Other possible tests:
1. join on `t1.optional_id = t2.optional_id` (would expect filters on both join inputs)
2. `LEFT join on t1.optional = t2.id1 (negative test, expect nothing)
##########
datafusion/optimizer/src/filter_null_join_keys.rs:
##########
@@ -0,0 +1,247 @@
+// 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.
+
+//! The FilterNullJoinKeys rule will identify inner joins with equi-join conditions
+//! where the join key is nullable on one side and non-nullable on the other side
+//! and then insert an `IsNotNull` filter on the nullable side since null values
+//! can never match.
Review Comment:
I think this could also push `IsNotNull` filters when both sides were nullable 🤔
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