datafusion_optimizer/
eliminate_join.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18//! [`EliminateJoin`] rewrites `INNER JOIN` with `true`/`null`
19use crate::optimizer::ApplyOrder;
20use crate::{OptimizerConfig, OptimizerRule};
21use datafusion_common::tree_node::Transformed;
22use datafusion_common::{Result, ScalarValue};
23use datafusion_expr::JoinType::Inner;
24use datafusion_expr::{
25    logical_plan::{EmptyRelation, LogicalPlan},
26    Expr,
27};
28
29/// Eliminates joins when join condition is false.
30/// Replaces joins when inner join condition is true with a cross join.
31#[derive(Default, Debug)]
32pub struct EliminateJoin;
33
34impl EliminateJoin {
35    pub fn new() -> Self {
36        Self {}
37    }
38}
39
40impl OptimizerRule for EliminateJoin {
41    fn name(&self) -> &str {
42        "eliminate_join"
43    }
44
45    fn apply_order(&self) -> Option<ApplyOrder> {
46        Some(ApplyOrder::TopDown)
47    }
48
49    fn rewrite(
50        &self,
51        plan: LogicalPlan,
52        _config: &dyn OptimizerConfig,
53    ) -> Result<Transformed<LogicalPlan>> {
54        match plan {
55            LogicalPlan::Join(join) if join.join_type == Inner && join.on.is_empty() => {
56                match join.filter {
57                    Some(Expr::Literal(ScalarValue::Boolean(Some(false)), _)) => Ok(
58                        Transformed::yes(LogicalPlan::EmptyRelation(EmptyRelation {
59                            produce_one_row: false,
60                            schema: join.schema,
61                        })),
62                    ),
63                    _ => Ok(Transformed::no(LogicalPlan::Join(join))),
64                }
65            }
66            _ => Ok(Transformed::no(plan)),
67        }
68    }
69
70    fn supports_rewrite(&self) -> bool {
71        true
72    }
73}
74
75#[cfg(test)]
76mod tests {
77    use crate::assert_optimized_plan_eq_snapshot;
78    use crate::eliminate_join::EliminateJoin;
79    use crate::OptimizerContext;
80    use datafusion_common::Result;
81    use datafusion_expr::JoinType::Inner;
82    use datafusion_expr::{lit, logical_plan::builder::LogicalPlanBuilder};
83    use std::sync::Arc;
84
85    macro_rules! assert_optimized_plan_equal {
86        (
87            $plan:expr,
88            @ $expected:literal $(,)?
89        ) => {{
90            let optimizer_ctx = OptimizerContext::new().with_max_passes(1);
91            let rules: Vec<Arc<dyn crate::OptimizerRule + Send + Sync>> = vec![Arc::new(EliminateJoin::new())];
92            assert_optimized_plan_eq_snapshot!(
93                optimizer_ctx,
94                rules,
95                $plan,
96                @ $expected,
97            )
98        }};
99    }
100
101    #[test]
102    fn join_on_false() -> Result<()> {
103        let plan = LogicalPlanBuilder::empty(false)
104            .join_on(
105                LogicalPlanBuilder::empty(false).build()?,
106                Inner,
107                Some(lit(false)),
108            )?
109            .build()?;
110
111        assert_optimized_plan_equal!(plan, @"EmptyRelation: rows=0")
112    }
113}
datafusion_optimizer/eliminate_join.rs

datafusion_optimizer/
eliminate_join.rs
