datafusion-physical-optimizer 45.0.0

DataFusion Physical Optimizer
Documentation 
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// 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.

//! This file implements the `ProjectionPushdown` physical optimization rule.
//! The function [`remove_unnecessary_projections`] tries to push down all
//! projections one by one if the operator below is amenable to this. If a
//! projection reaches a source, it can even disappear from the plan entirely.

use std::sync::Arc;

use crate::PhysicalOptimizerRule;

use datafusion_common::config::ConfigOptions;
use datafusion_common::tree_node::{TransformedResult, TreeNode};
use datafusion_common::Result;
use datafusion_physical_plan::projection::remove_unnecessary_projections;
use datafusion_physical_plan::ExecutionPlan;

/// This rule inspects `ProjectionExec`'s in the given physical plan and tries to
/// remove or swap with its child.
#[derive(Default, Debug)]
pub struct ProjectionPushdown {}

impl ProjectionPushdown {
    #[allow(missing_docs)]
    pub fn new() -> Self {
        Self {}
    }
}

impl PhysicalOptimizerRule for ProjectionPushdown {
    fn optimize(
        &self,
        plan: Arc<dyn ExecutionPlan>,
        _config: &ConfigOptions,
    ) -> Result<Arc<dyn ExecutionPlan>> {
        plan.transform_down(remove_unnecessary_projections).data()
    }

    fn name(&self) -> &str {
        "ProjectionPushdown"
    }

    fn schema_check(&self) -> bool {
        true
    }
}