repr: don't allocate while parsing floats (#5341)

parse_float32/-3.0      time:   [41.721 ns 41.940 ns 42.170 ns]
                        change: [-55.287% -55.053% -54.764%] (p = 0.00 < 0.05)
                        Performance has improved.

parse_float32/9.7       time:   [41.411 ns 41.671 ns 41.918 ns]
                        change: [-49.983% -49.783% -49.552%] (p = 0.00 < 0.05)
                        Performance has improved.

parse_float32/NaN       time:   [25.068 ns 25.253 ns 25.447 ns]
                        change: [-60.892% -60.692% -60.434%] (p = 0.00 < 0.05)
                        Performance has improved.

parse_float32/inFiNiTy  time:   [16.827 ns 16.840 ns 16.852 ns]
                        change: [-86.343% -86.325% -86.307%] (p = 0.00 < 0.05)
                        Performance has improved.

Author: benesch

src/repr/benches/strconv.rs

@@ -7,13 +7,26 @@
 // the Business Source License, use of this software will be governed
 // by the Apache License, Version 2.0.
 
-use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion};
 use rand::rngs::StdRng;
 use rand::seq::SliceRandom;
 use rand::{Rng, SeedableRng};
 
 use repr::strconv;
 
+fn bench_parse_float32(c: &mut Criterion) {
+    for s in &["-3.0", "9.7", "NaN", "inFiNiTy"] {
+        c.bench_with_input(BenchmarkId::new("parse_float32", s), s, |b, s| {
+            b.iter(|| strconv::parse_float32(s).unwrap())
+        });
+    }
+
+    let input = include_str!("testdata/twitter.json");
+    c.bench_function("parse_jsonb", |b| {
+        b.iter(|| black_box(strconv::parse_jsonb(input).unwrap()))
+    });
+}
+
 fn bench_parse_jsonb(c: &mut Criterion) {
     let input = include_str!("testdata/twitter.json");
     c.bench_function("parse_jsonb", |b| {
@@ -73,6 +86,7 @@ criterion_group!(
     benches,
     bench_format_list_simple,
     bench_format_list_nested,
+    bench_parse_float32,
     bench_parse_jsonb
 );
 criterion_main!(benches);

src/repr/src/strconv.rs

@@ -34,6 +34,7 @@ use ore::lex::LexBuf;
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
+use ore::ascii::UncasedStr;
 use ore::fmt::FormatBuffer;
 
 use crate::adt::array::ArrayDimension;
@@ -126,13 +127,17 @@ where
 
 /// Parses an `f32` from `s`.
 pub fn parse_float32(s: &str) -> Result<f32, ParseError> {
-    match s.trim().to_lowercase().as_str() {
-        "inf" | "infinity" | "+inf" | "+infinity" => Ok(f32::INFINITY),
-        "-inf" | "-infinity" => Ok(f32::NEG_INFINITY),
-        "nan" => Ok(f32::NAN),
-        s => s
+    let s = UncasedStr::new(s.trim());
+    if s == "inf" || s == "infinity" || s == "+inf" || s == "+infinity" {
+        Ok(f32::INFINITY)
+    } else if s == "-inf" || s == "-infinity" {
+        Ok(f32::NEG_INFINITY)
+    } else if s == "nan" {
+        Ok(f32::NAN)
+    } else {
+        s.as_str()
             .parse()
-            .map_err(|e| ParseError::new("float4", s).with_details(e)),
+            .map_err(|e| ParseError::new("float4", s.as_str()).with_details(e))
     }
 }
 
@@ -155,13 +160,17 @@ where
 
 /// Parses an `f64` from `s`.
 pub fn parse_float64(s: &str) -> Result<f64, ParseError> {
-    match s.trim().to_lowercase().as_str() {
-        "inf" | "infinity" | "+inf" | "+infinity" => Ok(f64::INFINITY),
-        "-inf" | "-infinity" => Ok(f64::NEG_INFINITY),
-        "nan" => Ok(f64::NAN),
-        s => s
+    let s = UncasedStr::new(s.trim());
+    if s == "inf" || s == "infinity" || s == "+inf" || s == "+infinity" {
+        Ok(f64::INFINITY)
+    } else if s == "-inf" || s == "-infinity" {
+        Ok(f64::NEG_INFINITY)
+    } else if s == "nan" {
+        Ok(f64::NAN)
+    } else {
+        s.as_str()
             .parse()
-            .map_err(|e| ParseError::new("float8", s).with_details(e)),
+            .map_err(|e| ParseError::new("float8", s.as_str()).with_details(e))
     }
 }