lance 0.19.2

A columnar data format that is 100x faster than Parquet for random access.
Documentation 
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// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: Copyright The Lance Authors

//! Lance Physical Optimizer Rules

use std::sync::Arc;

use super::TakeExec;
use datafusion::{
    common::tree_node::{Transformed, TreeNode},
    config::ConfigOptions,
    error::Result as DFResult,
    physical_optimizer::{optimizer::PhysicalOptimizer, PhysicalOptimizerRule},
    physical_plan::{projection::ProjectionExec as DFProjectionExec, ExecutionPlan},
};
use datafusion_physical_expr::expressions::Column;

/// Rule that eliminates [TakeExec] nodes that are immediately followed by another [TakeExec].
pub struct CoalesceTake;

impl PhysicalOptimizerRule for CoalesceTake {
    fn optimize(
        &self,
        plan: Arc<dyn ExecutionPlan>,
        _config: &ConfigOptions,
    ) -> DFResult<Arc<dyn ExecutionPlan>> {
        Ok(plan
            .transform_down(|plan| {
                if let Some(take) = plan.as_any().downcast_ref::<TakeExec>() {
                    let child = take.children()[0];
                    if let Some(exec_child) = child.as_any().downcast_ref::<TakeExec>() {
                        let inner_child = exec_child.children()[0].clone();
                        return Ok(Transformed::yes(plan.with_new_children(vec![inner_child])?));
                    }
                }
                Ok(Transformed::no(plan))
            })?
            .data)
    }

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

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

/// Rule that eliminates [ProjectionExec] nodes that projects all columns
/// from its input with no additional expressions.
pub struct SimplifyProjection;

impl PhysicalOptimizerRule for SimplifyProjection {
    fn optimize(
        &self,
        plan: Arc<dyn ExecutionPlan>,
        _config: &ConfigOptions,
    ) -> DFResult<Arc<dyn ExecutionPlan>> {
        Ok(plan
            .transform_down(|plan| {
                if let Some(proj) = plan.as_any().downcast_ref::<DFProjectionExec>() {
                    let children = proj.children();
                    if children.len() != 1 {
                        return Ok(Transformed::no(plan));
                    }

                    let input = children[0];

                    // TODO: we could try to coalesce consecutive projections, something for later
                    // For now, we just keep things simple and only remove NoOp projections

                    // output has different schema, projection needed
                    if input.schema() != proj.schema() {
                        return Ok(Transformed::no(plan));
                    }

                    if proj.expr().iter().enumerate().all(|(index, (expr, name))| {
                        if let Some(expr) = expr.as_any().downcast_ref::<Column>() {
                            // no renaming, no reordering
                            expr.index() == index && expr.name() == name
                        } else {
                            false
                        }
                    }) {
                        return Ok(Transformed::yes(input.clone()));
                    }
                }
                Ok(Transformed::no(plan))
            })?
            .data)
    }

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

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

pub fn get_physical_optimizer() -> PhysicalOptimizer {
    PhysicalOptimizer::with_rules(vec![
        Arc::new(crate::io::exec::optimizer::CoalesceTake),
        Arc::new(crate::io::exec::optimizer::SimplifyProjection),
    ])
}