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new 738e69ccfc bench(arrow-cast): Add decimal formatting benchmark (#10997)
738e69ccfc is described below
commit 738e69ccfc90e1cb90ab5a622b4c32f8ebc3409f
Author: Neil Conway <[email protected]>
AuthorDate: Sat Sep 5 21:26:22 2026 -0400
bench(arrow-cast): Add decimal formatting benchmark (#10997)
# Which issue does this PR close?
- N/A
# Rationale for this change
Add `format_decimal.rs`, which formats arrays of 8192 random values
through ArrayFormatter like `format_temporal.rs` does, for Decimal32,
Decimal64, Decimal128 and Decimal256 at representative precisions and
scales, with digit counts that cover values below the scale, values that
fit an i128 and the widest Decimal256 values.
There was previously no benchmark that covered formatting decimals.
# What changes are included in this PR?
See above.
# Are these changes tested?
Yes.
# Are there any user-facing changes?
No.
---
arrow-cast/Cargo.toml | 4 ++
arrow-cast/benches/format_decimal.rs | 111 +++++++++++++++++++++++++++++++++++
2 files changed, 115 insertions(+)
diff --git a/arrow-cast/Cargo.toml b/arrow-cast/Cargo.toml
index 5e8432949f..79af3d3da7 100644
--- a/arrow-cast/Cargo.toml
+++ b/arrow-cast/Cargo.toml
@@ -83,3 +83,7 @@ harness = false
[lints]
workspace = true
+
+[[bench]]
+name = "format_decimal"
+harness = false
diff --git a/arrow-cast/benches/format_decimal.rs
b/arrow-cast/benches/format_decimal.rs
new file mode 100644
index 0000000000..50730828ea
--- /dev/null
+++ b/arrow-cast/benches/format_decimal.rs
@@ -0,0 +1,111 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::hint::black_box;
+
+use arrow_array::ArrowNativeTypeOp;
+use arrow_array::types::{
+ Decimal32Type, Decimal64Type, Decimal128Type, Decimal256Type, DecimalType,
+};
+use arrow_array::{Array, ArrayRef, PrimitiveArray};
+use arrow_buffer::ArrowNativeType;
+use arrow_cast::display::{ArrayFormatter, FormatOptions};
+use criterion::{BenchmarkId, Criterion, Throughput, criterion_group,
criterion_main};
+use rand::rngs::StdRng;
+use rand::{RngExt, SeedableRng};
+use std::sync::Arc;
+
+const ARRAY_LEN: usize = 8192;
+
+/// Creates an array of [`ARRAY_LEN`] random values with `digits` significant
+/// digits (no leading zero, half of them negative) for the given `precision`
+/// and `scale`
+fn decimal_array<T: DecimalType>(digits: u32, precision: u8, scale: i8) ->
ArrayRef {
+ let mut rng = StdRng::seed_from_u64(42);
+ let ten = T::Native::usize_as(10);
+ let values = (0..ARRAY_LEN).map(|_| {
+ let mut value = T::Native::usize_as(rng.random_range(1..10));
+ for _ in 1..digits {
+ value = value
+ .mul_wrapping(ten)
+ .add_wrapping(T::Native::usize_as(rng.random_range(0..10)));
+ }
+ if rng.random::<bool>() {
+ value.neg_wrapping()
+ } else {
+ value
+ }
+ });
+ let array = PrimitiveArray::<T>::from_iter_values(values)
+ .with_precision_and_scale(precision, scale)
+ .unwrap();
+ Arc::new(array)
+}
+
+fn format_array(c: &mut Criterion) {
+ let mut group = c.benchmark_group("format_decimal");
+ group.throughput(Throughput::Elements(ARRAY_LEN as u64));
+
+ for (id, array) in [
+ (
+ BenchmarkId::new("decimal32", "(9, 2) 9 digits"),
+ decimal_array::<Decimal32Type>(9, 9, 2),
+ ),
+ (
+ BenchmarkId::new("decimal64", "(18, 6) 18 digits"),
+ decimal_array::<Decimal64Type>(18, 18, 6),
+ ),
+ (
+ BenchmarkId::new("decimal128", "(10, 2) 1 digit"),
+ decimal_array::<Decimal128Type>(1, 10, 2),
+ ),
+ (
+ BenchmarkId::new("decimal128", "(10, 2) 5 digits"),
+ decimal_array::<Decimal128Type>(5, 10, 2),
+ ),
+ (
+ BenchmarkId::new("decimal128", "(38, 10) 38 digits"),
+ decimal_array::<Decimal128Type>(38, 38, 10),
+ ),
+ (
+ BenchmarkId::new("decimal256", "(76, 10) 38 digits"),
+ decimal_array::<Decimal256Type>(38, 76, 10),
+ ),
+ (
+ BenchmarkId::new("decimal256", "(76, 10) 76 digits"),
+ decimal_array::<Decimal256Type>(76, 76, 10),
+ ),
+ ] {
+ let formatter = ArrayFormatter::try_new(array.as_ref(),
&FormatOptions::new()).unwrap();
+ let mut output = String::with_capacity(128);
+
+ group.bench_function(id, |b| {
+ b.iter(|| {
+ for idx in 0..array.len() {
+ output.clear();
+ formatter.value(idx).write(&mut output).unwrap();
+ }
+ black_box(&output);
+ })
+ });
+ }
+
+ group.finish();
+}
+
+criterion_group!(benches, format_array);
+criterion_main!(benches);
