From 1a880d632e96179d10f2bcf06b573a8faa21b7c8 Mon Sep 17 00:00:00 2001
From: Vrishabh <psvrishabh@gmail.com>
Date: Sun, 18 Feb 2024 16:51:03 +0530
Subject: [PATCH] Improve float to string cast by ~20%-40% (#5401)

* Add cast f64 to string to benchmark

* Improve float to string performance using ryu
---
 arrow-cast/Cargo.toml         |  1 +
 arrow-cast/src/display.rs     | 16 +++++++++++++++-
 arrow/benches/cast_kernels.rs |  4 +++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arrow-cast/Cargo.toml b/arrow-cast/Cargo.toml
index 81dd0ebd415f..2d8a57aba5f5 100644
--- a/arrow-cast/Cargo.toml
+++ b/arrow-cast/Cargo.toml
@@ -52,6 +52,7 @@ lexical-core = { version = "^0.8", default-features = false, features = ["write-
 atoi = "2.0.0"
 comfy-table = { version = "7.0", optional = true, default-features = false }
 base64 = "0.21"
+ryu = "1.0.16"
 
 [dev-dependencies]
 criterion = { version = "0.5", default-features = false }
diff --git a/arrow-cast/src/display.rs b/arrow-cast/src/display.rs
index d74128a20ba3..9ec12f6e63d2 100644
--- a/arrow-cast/src/display.rs
+++ b/arrow-cast/src/display.rs
@@ -427,9 +427,23 @@ macro_rules! primitive_display {
     };
 }
 
+macro_rules! primitive_display_float {
+    ($($t:ty),+) => {
+        $(impl<'a> DisplayIndex for &'a PrimitiveArray<$t>
+        {
+            fn write(&self, idx: usize, f: &mut dyn Write) -> FormatResult {
+                let value = self.value(idx);
+                let mut buffer = ryu::Buffer::new();
+                f.write_str(buffer.format(value))?;
+                Ok(())
+            }
+        })+
+    };
+}
+
 primitive_display!(Int8Type, Int16Type, Int32Type, Int64Type);
 primitive_display!(UInt8Type, UInt16Type, UInt32Type, UInt64Type);
-primitive_display!(Float32Type, Float64Type);
+primitive_display_float!(Float32Type, Float64Type);
 
 impl<'a> DisplayIndex for &'a PrimitiveArray<Float16Type> {
     fn write(&self, idx: usize, f: &mut dyn Write) -> FormatResult {
diff --git a/arrow/benches/cast_kernels.rs b/arrow/benches/cast_kernels.rs
index 933ddd4a06b4..6632dbc57c56 100644
--- a/arrow/benches/cast_kernels.rs
+++ b/arrow/benches/cast_kernels.rs
@@ -207,7 +207,9 @@ fn add_benchmark(c: &mut Criterion) {
     c.bench_function("cast f32 to string 512", |b| {
         b.iter(|| cast_array(&f32_array, DataType::Utf8))
     });
-
+    c.bench_function("cast f64 to string 512", |b| {
+        b.iter(|| cast_array(&f64_array, DataType::Utf8))
+    });
     c.bench_function("cast timestamp_ms to i64 512", |b| {
         b.iter(|| cast_array(&time_ms_array, DataType::Int64))
     });