refactoring index meta service

Author: anidotnet

nitrite/src/main/java/org/dizitart/no2/internals/IndexMetaService.java

@@ -45,15 +45,11 @@
  */
 class IndexMetaService {
     private final NitriteMap<NitriteId, Document> underlyingMap;
-    private final NitriteMap<String, IndexMeta> indexMetadata;
-    private final Map<String, Object> fieldLock;
     private final NitriteStore mvStore;
 
     IndexMetaService(NitriteMap<NitriteId, Document> underlyingMap) {
         this.underlyingMap = underlyingMap;
         this.mvStore = underlyingMap.getStore();
-        indexMetadata = getIndexMetadata();
-        this.fieldLock = new ConcurrentHashMap<>();
     }
 
     NitriteMap<NitriteId, Document> getUnderlyingMap() {
@@ -147,15 +143,6 @@ Index createIndexMetadata(String field, IndexType indexType) {
         return index;
     }
 
-    synchronized Object getFieldLock(String field) {
-        Object lock = fieldLock.get(field);
-        if (lock != null) return lock;
-
-        lock = new Object();
-        fieldLock.put(field, lock);
-        return lock;
-    }
-
     private String getName() {
         return INDEX_META_PREFIX + INTERNAL_NAME_SEPARATOR + underlyingMap.getName();
     }