Avoid quadratic index updates in uv add

crates/uv-bench/Cargo.toml

@@ -33,6 +33,11 @@ name = "uv_pep440"
 path = "benches/uv_pep440.rs"
 harness = false
 
+[[bench]]
+name = "add_indexes"
+path = "benches/add_indexes.rs"
+harness = false
+
 [dev-dependencies]
 uv = { workspace = true }
 uv-cache = { workspace = true }

crates/uv-bench/benches/add_indexes.rs

@@ -0,0 +1,71 @@
+//! Benchmarks updating a `pyproject.toml` with many configured indexes.
+
+extern crate uv_performance_memory_allocator;
+
+use std::hint::black_box;
+use std::path::Path;
+use std::str::FromStr;
+
+use criterion::{BatchSize, Criterion, criterion_group, criterion_main};
+
+use uv_distribution_types::Index;
+use uv_workspace::pyproject_mut::{DependencyTarget, PyProjectTomlMut};
+
+fn add_indexes(criterion: &mut Criterion) {
+    let mut group = criterion.benchmark_group("add_indexes");
+
+    for size in [32, 128, 512, 2048] {
+        let indexes = (0..size)
+            .map(|index| {
+                Index::from_str(&format!("idx-{index}=https://index-{index}.example/simple"))
+                    .expect("valid index")
+            })
+            .collect::<Vec<_>>();
+        let references = indexes.iter().collect::<Vec<_>>();
+
+        group.bench_function(format!("individual/{size}"), |bench| {
+            bench.iter_batched(
+                || {
+                    PyProjectTomlMut::from_toml(
+                        "[project]\nname = \"project\"\n",
+                        DependencyTarget::PyProjectToml,
+                    )
+                    .expect("valid pyproject.toml")
+                },
+                |mut pyproject| {
+                    for index in references.iter().rev() {
+                        pyproject
+                            .add_index(black_box(index), Path::new("."))
+                            .expect("valid index table");
+                    }
+                    black_box(pyproject);
+                },
+                BatchSize::SmallInput,
+            );
+        });
+
+        group.bench_function(format!("batched/{size}"), |bench| {
+            bench.iter_batched(
+                || {
+                    PyProjectTomlMut::from_toml(
+                        "[project]\nname = \"project\"\n",
+                        DependencyTarget::PyProjectToml,
+                    )
+                    .expect("valid pyproject.toml")
+                },
+                |mut pyproject| {
+                    pyproject
+                        .add_indexes(black_box(&references), Path::new("."))
+                        .expect("valid index tables");
+                    black_box(pyproject);
+                },
+                BatchSize::SmallInput,
+            );
+        });
+    }
+
+    group.finish();
+}
+
+criterion_group!(add_indexes_benches, add_indexes);
+criterion_main!(add_indexes_benches);