--- mysql-8.0.31/sql/binlog_ostream.cc	2022-11-17 19:28:38.972797713 +0800
+++ mysql-8.0.31/sql/binlog_ostream.cc	2022-11-17 19:29:32.096066949 +0800
@@ -182,7 +182,7 @@
 
 bool IO_CACHE_binlog_cache_storage::next(unsigned char **buffer,
                                          my_off_t *length) {
-  my_b_fill(&m_io_cache);
+  if (my_b_bytes_in_cache(&m_io_cache) == 0) my_b_fill(&m_io_cache);
 
   *buffer = m_io_cache.read_pos;
   *length = my_b_bytes_in_cache(&m_io_cache);