datafusion 10.0.0

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//
//   http://www.apache.org/licenses/LICENSE-2.0
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//! Collection of utility functions that are leveraged by the query optimizer rules

use super::optimizer::PhysicalOptimizerRule;
use crate::execution::context::SessionConfig;

use crate::error::Result;
use crate::physical_plan::{with_new_children_if_necessary, ExecutionPlan};
use std::sync::Arc;

/// Convenience rule for writing optimizers: recursively invoke
/// optimize on plan's children and then return a node of the same
/// type. Useful for optimizer rules which want to leave the type
/// of plan unchanged but still apply to the children.
pub fn optimize_children(
    optimizer: &impl PhysicalOptimizerRule,
    plan: Arc<dyn ExecutionPlan>,
    session_config: &SessionConfig,
) -> Result<Arc<dyn ExecutionPlan>> {
    let children = plan
        .children()
        .iter()
        .map(|child| optimizer.optimize(Arc::clone(child), session_config))
        .collect::<Result<Vec<_>>>()?;

    if children.is_empty() {
        Ok(Arc::clone(&plan))
    } else {
        with_new_children_if_necessary(plan, children)
    }
}