diff --git a/be/src/util/coding.h b/be/src/util/coding.h
index 714c68abaa4ea3..57e839f6d1ecd7 100644
--- a/be/src/util/coding.h
+++ b/be/src/util/coding.h
@@ -143,7 +143,10 @@ extern uint8_t* encode_varint64(uint8_t* dst, uint64_t value);
 inline uint8_t* encode_varint64(uint8_t* dst, uint64_t v) {
     static const unsigned int B = 128;
     while (v >= B) {
-        *(dst++) = (v & (B - 1)) | B;
+        // Fetch low seven bits from current v, and the eight bit is marked as compression mark.
+        // v | B is optimsed from (v & (B-1)) | B, because result is assgined to uint8_t and other bits 
+        // is cleared by implicit conversion.
+        *(dst++) = v | B;
         v >>= 7;
     }
     *(dst++) = static_cast<unsigned char>(v);