diff --git a/core/src/db/meta/MetaConsts.h b/core/src/db/meta/MetaConsts.h
index c21a749fc8671d345b086c15d3a15dd0e4664157..0c77dc259945ebd8eb830d327444d00af098b22d 100644
--- a/core/src/db/meta/MetaConsts.h
+++ b/core/src/db/meta/MetaConsts.h
@@ -32,7 +32,12 @@ const size_t H_SEC = 60 * M_SEC;
 const size_t D_SEC = 24 * H_SEC;
 const size_t W_SEC = 7 * D_SEC;
 
-const size_t BUILD_INDEX_THRESHOLD = 1000;
+// This value is to ignore small raw files when building index.
+// The reason is:
+// 1. The performance of brute-search for small raw files could be better than small index file.
+// 2. And small raw files can be merged to larger files, thus reduce fragmented files count.
+// We decide the value based on a testing for small size raw/index files.
+const size_t BUILD_INDEX_THRESHOLD = 5000;
 
 }  // namespace meta
 }  // namespace engine