datafusion_physical_plan/
tree_node.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//! This module provides common traits for visiting or rewriting tree nodes easily.
19
20use std::fmt::{self, Display, Formatter};
21use std::sync::Arc;
22
23use crate::execution_plan::replace_children_if_necessary;
24use crate::{ExecutionPlan, displayable};
25
26use datafusion_common::Result;
27use datafusion_common::tree_node::{ConcreteTreeNode, DynTreeNode};
28
29impl DynTreeNode for dyn ExecutionPlan {
30    fn arc_children(&self) -> Vec<&Arc<Self>> {
31        self.children()
32    }
33
34    fn with_new_arc_children(
35        &self,
36        arc_self: Arc<Self>,
37        new_children: Vec<Arc<Self>>,
38    ) -> Result<Arc<Self>> {
39        replace_children_if_necessary(arc_self, new_children)
40    }
41}
42
43/// A node context object beneficial for writing optimizer rules.
44/// This context encapsulating an [`ExecutionPlan`] node with a payload.
45///
46/// Since each wrapped node has it's children within both the `PlanContext.plan.children()`,
47/// as well as separately within the `PlanContext.children` (which are child nodes wrapped in the context),
48/// it's important to keep these child plans in sync when performing mutations.
49///
50/// Since there are two ways to access child plans directly -— it's recommended
51/// to perform mutable operations via [`Self::update_plan_from_children`].
52/// After mutating the `PlanContext.children`, or after creating the `PlanContext`,
53/// call `update_plan_from_children` to sync.
54#[derive(Debug)]
55pub struct PlanContext<T: Sized> {
56    /// The execution plan associated with this context.
57    pub plan: Arc<dyn ExecutionPlan>,
58    /// Custom data payload of the node.
59    pub data: T,
60    /// Child contexts of this node.
61    pub children: Vec<Self>,
62}
63
64impl<T> PlanContext<T> {
65    pub fn new(plan: Arc<dyn ExecutionPlan>, data: T, children: Vec<Self>) -> Self {
66        Self {
67            plan,
68            data,
69            children,
70        }
71    }
72
73    /// Update the `PlanContext.plan.children()` from the `PlanContext.children`,
74    /// if the `PlanContext.children` have been changed.
75    pub fn update_plan_from_children(mut self) -> Result<Self> {
76        let children_plans = self.children.iter().map(|c| Arc::clone(&c.plan)).collect();
77        self.plan = replace_children_if_necessary(self.plan, children_plans)?;
78
79        Ok(self)
80    }
81}
82
83impl<T: Default> PlanContext<T> {
84    pub fn new_default(plan: Arc<dyn ExecutionPlan>) -> Self {
85        let children = plan
86            .children()
87            .into_iter()
88            .cloned()
89            .map(Self::new_default)
90            .collect();
91        Self::new(plan, Default::default(), children)
92    }
93}
94
95impl<T: Display> Display for PlanContext<T> {
96    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
97        let node_string = displayable(self.plan.as_ref()).one_line();
98        write!(f, "Node plan: {node_string}")?;
99        write!(f, "Node data: {}", self.data)?;
100        write!(f, "")
101    }
102}
103
104impl<T> ConcreteTreeNode for PlanContext<T> {
105    fn children(&self) -> &[Self] {
106        &self.children
107    }
108
109    fn take_children(mut self) -> (Self, Vec<Self>) {
110        let children = std::mem::take(&mut self.children);
111        (self, children)
112    }
113
114    fn with_new_children(mut self, children: Vec<Self>) -> Result<Self> {
115        self.children = children;
116        self.update_plan_from_children()
117    }
118}
datafusion_physical_plan/tree_node.rs

datafusion_physical_plan/
tree_node.rs
