Improve performance of metric expression matcher (#5864)

Refactored env struct to avoid creating closure functions for every
expression evaluation operation. This reduced the allocations and
increased the speed.

Improvements:

$ benchstat old.txt new.txt
name          old time/op    new time/op    delta
ExprFilter-8     537µs ± 2%     476µs ± 1%  -11.33%  (p=0.000 n=9+10)

name          old alloc/op   new alloc/op   delta
ExprFilter-8     151kB ± 0%     102kB ± 0%  -32.43%  (p=0.000 n=8+8)

name          old allocs/op  new allocs/op  delta
ExprFilter-8     8.44k ± 0%     6.39k ± 0%  -24.24%  (p=0.000 n=10+10)

internal/coreinternal/processor/filterexpr/matcher.go

@@ -27,9 +27,17 @@ type Matcher struct {
 
 type env struct {
  MetricName string
- // TODO: replace this with GetLabel func(key string) (string,bool)
- HasLabel func(key string) bool
- Label func(key string) string
+ attributes pdata.AttributeMap
+}
+
+func (e *env) HasLabel(key string) bool {
+ _, ok := e.attributes.Get(key)
+ return ok
+}
+
+func (e *env) Label(key string) string {
+ v, _ := e.attributes.Get(key)
+ return v.StringVal()
 }
 
 func NewMatcher(expression string) (*Matcher, error) {
@@ -100,21 +108,14 @@ func (m *Matcher) matchEnv(metricName string, attributes pdata.AttributeMap) (bo
  return m.match(createEnv(metricName, attributes))
 }
 
-func createEnv(metricName string, attributes pdata.AttributeMap) env {
- return env{
+func createEnv(metricName string, attributes pdata.AttributeMap) *env {
+ return &env{
  MetricName: metricName,
- HasLabel: func(key string) bool {
- _, ok := attributes.Get(key)
- return ok
- },
- Label: func(key string) string {
- v, _ := attributes.Get(key)
- return v.StringVal()
- },
+ attributes: attributes,
  }
 }
 
-func (m *Matcher) match(env env) (bool, error) {
+func (m *Matcher) match(env *env) (bool, error) {
  result, err := m.v.Run(m.program, env)
  if err != nil {
  return false, err

internal/coreinternal/processor/filterexpr/matcher_test.go

@@ -30,7 +30,7 @@ func TestCompileExprError(t *testing.T) {
 func TestRunExprError(t *testing.T) {
  matcher, err := NewMatcher("foo")
  require.NoError(t, err)
- matched, _ := matcher.match(env{})
+ matched, _ := matcher.match(&env{})
  require.False(t, matched)
 }