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use crate::TransformArgs;
use mz_expr::visit::Visit;
use mz_expr::{MirRelationExpr, TableFunc};
#[derive(Debug)]
pub struct FlatMapToMap;
impl crate::Transform for FlatMapToMap {
#[tracing::instrument(
target = "optimizer"
level = "trace",
skip_all,
fields(path.segment = "flatmap_to_map")
)]
fn transform(
&self,
relation: &mut MirRelationExpr,
_: TransformArgs,
) -> Result<(), crate::TransformError> {
relation.visit_mut_post(&mut Self::action)?;
mz_repr::explain::trace_plan(&*relation);
Ok(())
}
}
impl FlatMapToMap {
pub fn action(relation: &mut MirRelationExpr) {
if let MirRelationExpr::FlatMap { func, exprs, .. } = relation {
if let TableFunc::Wrap { width, .. } = func {
if *width >= exprs.len() {
if let MirRelationExpr::FlatMap { exprs, input, .. } = relation.take_dangerous()
{
*relation = input.map(exprs);
}
}
}
}
}
}