leveldb3: add instant dropping bucket

weed/filer/leveldb3/leveldb3_store_bucket.go

@@ -0,0 +1,23 @@
+package leveldb
+
+import (
+	"github.com/chrislusf/seaweedfs/weed/filer"
+	"os"
+)
+
+var _ filer.BucketAware = (*LevelDB3Store)(nil)
+
+func (store *LevelDB3Store) OnBucketCreation(bucket string) {
+	store.createDB(bucket)
+}
+
+func (store *LevelDB3Store) OnBucketDeletion(bucket string) {
+	store.closeDB(bucket)
+	if bucket != "" { // just to make sure
+		os.RemoveAll(store.dir + "/" + bucket)
+	}
+}
+
+func (store *LevelDB3Store) CanDropWholeBucket() bool {
+	return true
+}