VictoriaMetrics/lib/bytesutil/fast_string_matcher.go
Aliaksandr Valialkin b4bb1477fe
lib/regexutil: cache MatchString results for unoptimized regexps
This increases relabeling performance by 3x for unoptimized regexs
2022-09-30 12:28:25 +03:00

49 lines
1.2 KiB
Go

package bytesutil
import (
"sync"
"sync/atomic"
)
// FastStringMatcher implements fast matcher for strings.
//
// It caches string match results and returns them back on the next calls
// without calling the matchFunc, which may be expensive.
type FastStringMatcher struct {
m atomic.Value
mLen uint64
matchFunc func(s string) bool
}
// NewFastStringMatcher creates new matcher, which applies matchFunc to strings passed to Match()
//
// matchFunc must return the same result for the same input.
func NewFastStringMatcher(matchFunc func(s string) bool) *FastStringMatcher {
var fsm FastStringMatcher
fsm.m.Store(&sync.Map{})
fsm.matchFunc = matchFunc
return &fsm
}
// Match applies matchFunc to s and returns the result.
func (fsm *FastStringMatcher) Match(s string) bool {
m := fsm.m.Load().(*sync.Map)
v, ok := m.Load(s)
if ok {
// Fast path - s match result is found in the cache.
bp := v.(*bool)
return *bp
}
// Slow path - run matchFunc for s and store the result in the cache.
b := fsm.matchFunc(s)
bp := &b
m.Store(s, bp)
n := atomic.AddUint64(&fsm.mLen, 1)
if n > 100e3 {
atomic.StoreUint64(&fsm.mLen, 0)
fsm.m.Store(&sync.Map{})
}
return b
}