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
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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::eliminate_join::EliminateJoin;
78    use crate::test::*;
79    use datafusion_common::Result;
80    use datafusion_expr::JoinType::Inner;
81    use datafusion_expr::{lit, logical_plan::builder::LogicalPlanBuilder, LogicalPlan};
82    use std::sync::Arc;
83
84    fn assert_optimized_plan_equal(plan: LogicalPlan, expected: &str) -> Result<()> {
85        assert_optimized_plan_eq(Arc::new(EliminateJoin::new()), plan, expected)
86    }
87
88    #[test]
89    fn join_on_false() -> Result<()> {
90        let plan = LogicalPlanBuilder::empty(false)
91            .join_on(
92                LogicalPlanBuilder::empty(false).build()?,
93                Inner,
94                Some(lit(false)),
95            )?
96            .build()?;
97
98        let expected = "EmptyRelation";
99        assert_optimized_plan_equal(plan, expected)
100    }
101}
datafusion_optimizer/eliminate_join.rs

datafusion_optimizer/
eliminate_join.rs
