backend: improve parse function performance in gtime package (#1238)

* have unit tests for parse function

* define benchmark test for parse function

* add one more test casae

* Improve the code

* fast return when the input is empty

Author: itsmylife

backend/gtime/gtime.go

@@ -1,6 +1,7 @@
 package gtime
 
 import (
+	"errors"
 	"fmt"
 	"regexp"
 	"strconv"
@@ -74,18 +75,47 @@ func ParseDuration(inp string) (time.Duration, error) {
 }
 
 func parse(inp string) (time.Duration, string, error) {
-	result := dateUnitPattern.FindSubmatch([]byte(inp))
+	if inp == "" {
+		return 0, "", backend.DownstreamError(errors.New("empty input"))
+	}
+
+	// Fast path for simple duration formats (no date units)
+	lastChar := inp[len(inp)-1]
+	if lastChar != 'd' && lastChar != 'w' && lastChar != 'M' && lastChar != 'y' {
+		dur, err := time.ParseDuration(inp)
+		return dur, "", err
+	}
+
+	// Check if the rest is a number for date units
+	numPart := inp[:len(inp)-1]
+	isNum := true
+	for _, c := range numPart {
+		if c < '0' || c > '9' {
+			isNum = false
+			break
+		}
+	}
+	if isNum {
+		num, err := strconv.Atoi(numPart)
+		if err != nil {
+			return 0, "", err
+		}
+		return time.Duration(num), string(lastChar), nil
+	}
+
+	// Fallback to regex for complex cases
+	result := dateUnitPattern.FindStringSubmatch(inp)
 	if len(result) != 3 {
 		dur, err := time.ParseDuration(inp)
 		return dur, "", err
 	}
 
-	num, err := strconv.Atoi(string(result[1]))
+	num, err := strconv.Atoi(result[1])
 	if err != nil {
 		return 0, "", err
 	}
 
-	return time.Duration(num), string(result[2]), nil
+	return time.Duration(num), result[2], nil
 }
 
 // FormatInterval converts a duration into the units that Grafana uses

backend/gtime/gtime_bench_test.go

@@ -4,6 +4,30 @@ import (
 	"testing"
 )
 
+// go test -benchmem -run=^$ -bench=BenchmarkParse$ github.com/grafana/grafana-plugin-sdk-go/backend/gtime/ -memprofile p_mem.out -count 6 | tee pmem.0.txt
+func BenchmarkParse(b *testing.B) {
+	testCases := []struct {
+		name  string
+		input string
+	}{
+		{"PureNumber", "30"},
+		{"SimpleUnit", "5s"},
+		{"ComplexUnit", "1h30m"},
+		{"DateUnit", "7d"},
+		{"MonthUnit", "3M"},
+		{"YearUnit", "1y"},
+	}
+
+	for _, tc := range testCases {
+		b.Run(tc.name, func(b *testing.B) {
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				_, _, _ = parse(tc.input)
+			}
+		})
+	}
+}
+
 // go test -benchmem -run=^$ -bench=BenchmarkParseIntervalStringToTimeDuration$ github.
 // com/grafana/grafana-plugin-sdk-go/backend/gtime/ -memprofile p_mem.out -count 6 | tee p_mem.txt
 func BenchmarkParseIntervalStringToTimeDuration(b *testing.B) {
@@ -26,6 +50,7 @@ func BenchmarkParseIntervalStringToTimeDuration(b *testing.B) {
 	for _, tc := range testCases {
 		b.Run(tc.name, func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
+				b.ResetTimer()
 				_, err := ParseIntervalStringToTimeDuration(tc.interval)
 				if err != nil {
 					b.Fatal(err)

backend/gtime/gtime_test.go

@@ -212,3 +212,125 @@ func TestRoundInterval(t *testing.T) {
 		})
 	}
 }
+
+func TestParse(t *testing.T) {
+	tests := []struct {
+		name         string
+		input        string
+		wantDur      time.Duration
+		wantPeriod   string
+		wantErrRegex *regexp.Regexp
+	}{
+		{
+			name:       "simple duration seconds",
+			input:      "30s",
+			wantDur:    30 * time.Second,
+			wantPeriod: "",
+		},
+		{
+			name:       "simple duration minutes",
+			input:      "5m",
+			wantDur:    5 * time.Minute,
+			wantPeriod: "",
+		},
+		{
+			name:       "simple duration minutes and seconds",
+			input:      "1m30s",
+			wantDur:    90 * time.Second,
+			wantPeriod: "",
+		},
+		{
+			name:       "complex duration",
+			input:      "1h30m",
+			wantDur:    90 * time.Minute,
+			wantPeriod: "",
+		},
+		{
+			name:       "days unit",
+			input:      "7d",
+			wantDur:    7,
+			wantPeriod: "d",
+		},
+		{
+			name:       "weeks unit",
+			input:      "2w",
+			wantDur:    2,
+			wantPeriod: "w",
+		},
+		{
+			name:       "months unit",
+			input:      "3M",
+			wantDur:    3,
+			wantPeriod: "M",
+		},
+		{
+			name:       "years unit",
+			input:      "1y",
+			wantDur:    1,
+			wantPeriod: "y",
+		},
+		{
+			name:         "invalid duration",
+			input:        "invalid",
+			wantErrRegex: regexp.MustCompile(`time: invalid duration "?invalid"?`),
+		},
+		{
+			name:         "invalid number",
+			input:        "abc1d",
+			wantErrRegex: regexp.MustCompile(`time: invalid duration "?abc1d"?`),
+		},
+		{
+			name:         "empty string",
+			input:        "",
+			wantErrRegex: regexp.MustCompile(`empty input`),
+		},
+		{
+			name:       "fast path - pure number with date unit",
+			input:      "30d",
+			wantDur:    30,
+			wantPeriod: "d",
+		},
+		{
+			name:       "fast path - pure number with week unit",
+			input:      "2w",
+			wantDur:    2,
+			wantPeriod: "w",
+		},
+		{
+			name:       "fast path - pure number with month unit",
+			input:      "6M",
+			wantDur:    6,
+			wantPeriod: "M",
+		},
+		{
+			name:       "fast path - pure number with year unit",
+			input:      "5y",
+			wantDur:    5,
+			wantPeriod: "y",
+		},
+		{
+			name:         "non-numeric prefix with date unit",
+			input:        "a5d",
+			wantErrRegex: regexp.MustCompile(`time: invalid duration "?a5d"?`),
+		},
+		{
+			name:         "mixed characters with date unit",
+			input:        "5a3d",
+			wantErrRegex: regexp.MustCompile(`time: unknown unit "a" in duration "5a3d"`),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotDur, gotPeriod, err := parse(tt.input)
+			if tt.wantErrRegex != nil {
+				require.Error(t, err)
+				require.Regexp(t, tt.wantErrRegex, err.Error())
+				return
+			}
+			require.NoError(t, err)
+			require.Equal(t, tt.wantDur, gotDur)
+			require.Equal(t, tt.wantPeriod, gotPeriod)
+		})
+	}
+}