BUG#36252805 Non existent binlog cache means empty

Problem:
Checking if binlog cache is empty requires creating it first, then it
will be empty. This causes sessions which never had or should not
have binlog cache to get one, thus consuming unnecessary resources
indefinitely.

Analysis:
It can be seen that binlog cache is created during for example rollback
although the binlog cache does not exists and thus have no content.
Several other places consider non existent binlog cache as empty.

Solution:
Change THD::is_binlog_cache_empty() to return true when binlog cache
does not exist and remove calls to create the binlog cache before
calling that function.

Change-Id: I87e43dcff33a46790d0d29bc8259e38a1d1bd0ed

Author: blaudden

sql/binlog.cc

@@ -9428,13 +9428,14 @@ bool THD::is_binlog_cache_empty(bool is_transactional) const {
   // If opt_bin_log==0, it is not safe to call thd_get_cache_mngr
   // because binlog_hton has not been completely set up.
   assert(opt_bin_log);
-  binlog_cache_mngr *cache_mngr = thd_get_cache_mngr(this);
 
-  // cache_mngr is NULL until we call thd->binlog_setup_trx_data, so
-  // we assert that this has been done.
-  assert(cache_mngr != nullptr);
+  binlog_cache_mngr *const cache_mngr = thd_get_cache_mngr(this);
+  if (cache_mngr == nullptr) {
+    // The cache has not been setup and is thus empty
+    return true;
+  }
 
-  binlog_cache_data *cache_data =
+  binlog_cache_data *const cache_data =
       cache_mngr->get_binlog_cache_data(is_transactional);
   assert(cache_data != nullptr);
 

sql/rpl_gtid_state.cc

@@ -925,8 +925,6 @@ void Gtid_state::update_gtids_impl_own_anonymous(THD *thd, bool *more_trx) {
     See comment for the update_gtids_impl_begin function.
   */
   if (opt_bin_log) {
-    // Needed before is_binlog_cache_empty.
-    thd->binlog_setup_trx_data();
     if (!thd->is_binlog_cache_empty(true)) {
       *more_trx = true;
       DBUG_PRINT("info", ("Transaction cache is non-empty: setting "