feat: improve syntax parser for pattern (#12489)

Author: cyriltovena

pkg/logql/log/pattern/parser.go

@@ -1,6 +1,9 @@
 package pattern
 
-import "fmt"
+import (
+	"fmt"
+	"sync"
+)
 
 const underscore = "_"
 
@@ -10,6 +13,19 @@ var tokens = map[int]string{
 	UNDERSCORE: underscore,
 }
 
+type parser struct {
+	p *exprParserImpl
+}
+
+var parserPool = sync.Pool{
+	New: func() interface{} {
+		p := &parser{
+			p: &exprParserImpl{},
+		}
+		return p
+	},
+}
+
 func init() {
 	// Improve the error messages coming out of yacc.
 	exprErrorVerbose = true
@@ -23,9 +39,13 @@ func parseExpr(input string) (expr, error) {
 }
 
 func parseExprBytes(input []byte) (expr, error) {
+	p := parserPool.Get().(*parser)
+	defer parserPool.Put(p)
+
 	l := newLexer()
 	l.setData(input)
-	e := exprNewParser().Parse(l)
+
+	e := p.p.Parse(l)
 	if e != 0 || len(l.errs) > 0 {
 		return nil, l.errs[0]
 	}

pkg/logql/log/pattern/parser_test.go

@@ -57,3 +57,14 @@ func Test_Parse(t *testing.T) {
 		require.Equal(t, tc.expected, actual)
 	}
 }
+
+var result expr
+
+func BenchmarkParseExpr(b *testing.B) {
+	var err error
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		result, err = parseExpr(`level=info <_> caller=main.go:107 msg="Starting Grafana Enterprise Traces" version="version=weekly-r138-f1920489, branch=weekly-r138, revision=f1920489"`)
+	}
+	require.NoError(b, err)
+}