add bloom filter to leveldb_store to improve fuse performance.

weed/filer/leveldb/leveldb_store.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"github.com/syndtr/goleveldb/leveldb"
 	leveldb_errors "github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/filter"
 	"github.com/syndtr/goleveldb/leveldb/opt"
 	leveldb_util "github.com/syndtr/goleveldb/leveldb/util"
 	"os"
@@ -48,6 +49,7 @@ func (store *LevelDBStore) initialize(dir string) (err error) {
 		BlockCacheCapacity:            32 * 1024 * 1024, // default value is 8MiB
 		WriteBuffer:                   16 * 1024 * 1024, // default value is 4MiB
 		CompactionTableSizeMultiplier: 10,
+		Filter:                        filter.NewBloomFilter(8), // false positive rate 0.02
 	}
 
 	if store.db, err = leveldb.OpenFile(dir, opts); err != nil {