Refactor cache lookup

- Remove multiple mutex locks in partial cache lookup
- Simplify return values

src/cache.go

@@ -34,9 +34,9 @@ func (cc *ChunkCache) Add(chunk *Chunk, key string, list []*Result) {
 }
 
 // Find is called to lookup ChunkCache
-func (cc *ChunkCache) Find(chunk *Chunk, key string) ([]*Result, bool) {
+func (cc *ChunkCache) Find(chunk *Chunk, key string) []*Result {
 	if len(key) == 0 || !chunk.IsFull() {
-		return nil, false
+		return nil
 	}
 
 	cc.mutex.Lock()
@@ -46,8 +46,36 @@ func (cc *ChunkCache) Find(chunk *Chunk, key string) ([]*Result, bool) {
 	if ok {
 		list, ok := (*qc)[key]
 		if ok {
-			return list, true
+			return list
 		}
 	}
-	return nil, false
+	return nil
+}
+
+func (cc *ChunkCache) Search(chunk *Chunk, key string) []*Result {
+	if len(key) == 0 || !chunk.IsFull() {
+		return nil
+	}
+
+	cc.mutex.Lock()
+	defer cc.mutex.Unlock()
+
+	qc, ok := cc.cache[chunk]
+	if !ok {
+		return nil
+	}
+
+	for idx := 1; idx < len(key); idx++ {
+		// [---------| ] | [ |---------]
+		// [--------|  ] | [  |--------]
+		// [-------|   ] | [   |-------]
+		prefix := key[:len(key)-idx]
+		suffix := key[idx:]
+		for _, substr := range [2]string{prefix, suffix} {
+			if cached, found := (*qc)[substr]; found {
+				return cached
+			}
+		}
+	}
+	return nil
 }