server: make long-data type no longer check nullBitmap (#7573)

server/conn_stmt.go

@@ -246,15 +246,23 @@ func parseStmtArgs(args []interface{}, boundParams [][]byte, nullBitmap, paramTy
 	var isNull bool
 
 	for i := 0; i < len(args); i++ {
-		if nullBitmap[i>>3]&(1<<(uint(i)%8)) > 0 {
-			args[i] = nil
-			continue
-		}
+		// if params had received via ComStmtSendLongData, use them directly.
+		// ref https://dev.mysql.com/doc/internals/en/com-stmt-send-long-data.html
+		// see clientConn#handleStmtSendLongData
 		if boundParams[i] != nil {
 			args[i] = boundParams[i]
 			continue
 		}
 
+		// check nullBitMap to determine the NULL arguments.
+		// ref https://dev.mysql.com/doc/internals/en/com-stmt-execute.html
+		// notice: some client(e.g. mariadb) will set nullBitMap even if data had be sent via ComStmtSendLongData,
+		// so this check need place after boundParam's check.
+		if nullBitmap[i>>3]&(1<<(uint(i)%8)) > 0 {
+			args[i] = nil
+			continue
+		}
+
 		if (i<<1)+1 >= len(paramTypes) {
 			return mysql.ErrMalformPacket
 		}