datafusion-expr 36.0.0

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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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//! Tree node implementation for logical plan

use crate::LogicalPlan;

use datafusion_common::tree_node::{TreeNode, TreeNodeVisitor, VisitRecursion};
use datafusion_common::{handle_tree_recursion, Result};

impl TreeNode for LogicalPlan {
    fn apply<F: FnMut(&Self) -> Result<VisitRecursion>>(
        &self,
        op: &mut F,
    ) -> Result<VisitRecursion> {
        // Compared to the default implementation, we need to invoke
        // [`Self::apply_subqueries`] before visiting its children
        handle_tree_recursion!(op(self)?);
        self.apply_subqueries(op)?;
        self.apply_children(&mut |node| node.apply(op))
    }

    /// To use, define a struct that implements the trait [`TreeNodeVisitor`] and then invoke
    /// [`LogicalPlan::visit`].
    ///
    /// For example, for a logical plan like:
    ///
    /// ```text
    /// Projection: id
    ///    Filter: state Eq Utf8(\"CO\")\
    ///       CsvScan: employee.csv projection=Some([0, 3])";
    /// ```
    ///
    /// The sequence of visit operations would be:
    /// ```text
    /// visitor.pre_visit(Projection)
    /// visitor.pre_visit(Filter)
    /// visitor.pre_visit(CsvScan)
    /// visitor.post_visit(CsvScan)
    /// visitor.post_visit(Filter)
    /// visitor.post_visit(Projection)
    /// ```
    fn visit<V: TreeNodeVisitor<N = Self>>(
        &self,
        visitor: &mut V,
    ) -> Result<VisitRecursion> {
        // Compared to the default implementation, we need to invoke
        // [`Self::visit_subqueries`] before visiting its children
        handle_tree_recursion!(visitor.pre_visit(self)?);
        self.visit_subqueries(visitor)?;
        handle_tree_recursion!(self.apply_children(&mut |node| node.visit(visitor))?);
        visitor.post_visit(self)
    }

    fn apply_children<F: FnMut(&Self) -> Result<VisitRecursion>>(
        &self,
        op: &mut F,
    ) -> Result<VisitRecursion> {
        for child in self.inputs() {
            handle_tree_recursion!(op(child)?)
        }
        Ok(VisitRecursion::Continue)
    }

    fn map_children<F>(self, transform: F) -> Result<Self>
    where
        F: FnMut(Self) -> Result<Self>,
    {
        let old_children = self.inputs();
        let new_children = old_children
            .iter()
            .map(|&c| c.clone())
            .map(transform)
            .collect::<Result<Vec<_>>>()?;

        // if any changes made, make a new child
        if old_children
            .into_iter()
            .zip(new_children.iter())
            .any(|(c1, c2)| c1 != c2)
        {
            self.with_new_exprs(self.expressions(), new_children)
        } else {
            Ok(self)
        }
    }
}