Util: Improve performance of strings.SplitString (#49115)

Replaces the regexp with calls to strings.ReplaceAll and strings.Fields
for simplicity and improved performance.

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

pkg/util/strings.go

@@ -3,7 +3,6 @@ package util
 import (
 	"fmt"
 	"math"
-	"regexp"
 	"strings"
 	"time"
 	"unicode"
@@ -34,7 +33,7 @@ func SplitString(str string) []string {
 		return []string{}
 	}
 
-	return regexp.MustCompile("[, ]+").Split(str, -1)
+	return strings.Fields(strings.ReplaceAll(str, ",", " "))
 }
 
 // GetAgeString returns a string representing certain time from years to minutes.

pkg/util/strings_test.go

@@ -58,6 +58,53 @@ func TestSplitString(t *testing.T) {
 	}
 }
 
+func BenchmarkSplitString(b *testing.B) {
+	b.Run("empty input", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			SplitString("")
+		}
+	})
+	b.Run("single string", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			SplitString("test")
+		}
+	})
+	b.Run("space-separated", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			SplitString("test1 test2 test3")
+		}
+	})
+	b.Run("comma-separated", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			SplitString("test1,test2,test3")
+		}
+	})
+	b.Run("comma-separated with spaces", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			SplitString("test1 , test2 test3")
+		}
+	})
+	b.Run("mixed commas and spaces", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			SplitString("test1 , test2 test3,test4")
+		}
+	})
+	b.Run("very long mixed", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			SplitString("test1 , test2 test3,test4, test5 test6 test7,test8 test9 test10" +
+				" test11 test12 test13,test14 test15 test16,test17 test18 test19,test20 test21 test22" +
+				" test23,test24 test25 test26,test27 test28 test29,test30 test31 test32" +
+				" test33,test34 test35 test36,test37 test38 test39,test40 test41 test42" +
+				" test43,test44 test45 test46,test47 test48 test49,test50 test51 test52" +
+				" test53,test54 test55 test56,test57 test58 test59,test60 test61 test62" +
+				" test63,test64 test65 test66,test67 test68 test69,test70 test71 test72" +
+				" test73,test74 test75 test76,test77 test78 test79,test80 test81 test82" +
+				" test83,test84 test85 test86,test87 test88 test89,test90 test91 test92" +
+				" test93,test94 test95 test96,test97 test98 test99,test100 ")
+		}
+	})
+}
+
 func TestDateAge(t *testing.T) {
 	assert.Equal(t, "?", GetAgeString(time.Time{})) // base case