MDEV-25334 FTWRL/Backup blocks DDL on temporary tables with binlog enabled, assertion fails in Diagnostics_area::set_error_status

Fixed by adding a MDL_BACKUP_COMMIT lock before altering temporary tables
whose creation was logged to binary log (in which case the ALTER TABLE
must also be logged)

mysql-test/main/backup_lock_binlog.result

@@ -0,0 +1,40 @@
+#
+# MDEV-25334 FTWRL/Backup blocks DDL on temporary tables with binlog
+#            enabled assertion fails in Diagnostics_area::set_error_status
+#
+select @@binlog_format;
+@@binlog_format
+MIXED
+connect  con1,localhost,root,,;
+connection default;
+#
+# Test 1
+#
+CREATE TEMPORARY TABLE tmp (a INT);
+connection con1;
+FLUSH TABLES WITH READ LOCK;
+connection default;
+SET lock_wait_timeout= 1;
+ALTER TABLE tmp;
+ERROR HY000: Lock wait timeout exceeded; try restarting transaction
+connection con1;
+unlock tables;
+connection default;
+drop table tmp;
+#
+# Test 2 (In statement format to ensure temporary table gets logged)
+#
+set @@binlog_format=statement;
+CREATE TEMPORARY TABLE tmp (a INT);
+connection con1;
+BACKUP STAGE START;
+BACKUP STAGE BLOCK_COMMIT;
+connection default;
+SET lock_wait_timeout= 1;
+ALTER TABLE tmp;
+ERROR HY000: Lock wait timeout exceeded; try restarting transaction
+connection con1;
+BACKUP STAGE end;
+connection default;
+drop table tmp;
+disconnect con1;

mysql-test/main/backup_lock_binlog.test

@@ -0,0 +1,49 @@
+--source include/have_binlog_format_mixed_or_statement.inc
+
+#
+# Tests involving locks and binlog
+# 
+
+--echo #
+--echo # MDEV-25334 FTWRL/Backup blocks DDL on temporary tables with binlog
+--echo #            enabled assertion fails in Diagnostics_area::set_error_status
+--echo #
+
+select @@binlog_format;
+--connect (con1,localhost,root,,)
+connection default;
+
+--echo #
+--echo # Test 1
+--echo #
+
+CREATE TEMPORARY TABLE tmp (a INT);
+--connection con1
+FLUSH TABLES WITH READ LOCK;
+--connection default
+SET lock_wait_timeout= 1;
+--error ER_LOCK_WAIT_TIMEOUT
+ALTER TABLE tmp;
+--connection con1
+unlock tables;
+--connection default
+drop table tmp;
+
+--echo #
+--echo # Test 2 (In statement format to ensure temporary table gets logged)
+--echo #
+
+set @@binlog_format=statement;
+CREATE TEMPORARY TABLE tmp (a INT);
+--connection con1
+BACKUP STAGE START;
+BACKUP STAGE BLOCK_COMMIT;
+--connection default
+SET lock_wait_timeout= 1;
+--error ER_LOCK_WAIT_TIMEOUT
+ALTER TABLE tmp;
+--connection con1
+BACKUP STAGE end;
+--connection default
+drop table tmp;
+--disconnect con1

sql/sql_table.cc

@@ -9574,7 +9574,8 @@ bool mysql_alter_table(THD *thd, const LEX_CSTRING *new_db,
         If such table exists, there must be a corresponding TABLE_SHARE in
         THD::all_temp_tables list.
       */
-      if (thd->find_tmp_table_share(alter_ctx.new_db.str, alter_ctx.new_name.str))
+      if (thd->find_tmp_table_share(alter_ctx.new_db.str,
+                                    alter_ctx.new_name.str))
       {
         my_error(ER_TABLE_EXISTS_ERROR, MYF(0), alter_ctx.new_alias.str);
         DBUG_RETURN(true);
@@ -9715,6 +9716,17 @@ bool mysql_alter_table(THD *thd, const LEX_CSTRING *new_db,
 
   if (table->s->tmp_table == NO_TMP_TABLE)
     mysql_audit_alter_table(thd, table_list);
+  else if (table->s->table_creation_was_logged && mysql_bin_log.is_open())
+  {
+    /* Protect against MDL error in binary logging */
+    MDL_request mdl_request;
+    DBUG_ASSERT(!mdl_ticket);
+    mdl_request.init(MDL_key::BACKUP, "", "", MDL_BACKUP_COMMIT,
+                     MDL_TRANSACTION);
+    if (thd->mdl_context.acquire_lock(&mdl_request,
+                                      thd->variables.lock_wait_timeout))
+      DBUG_RETURN(true);
+  }
 
   THD_STAGE_INFO(thd, stage_setup);
 
@@ -9794,9 +9806,12 @@ do_continue:;
                 thd->get_stmt_da()->current_statement_warn_count());
     my_ok(thd, 0L, 0L, alter_ctx.tmp_buff);
 
-    /* We don't replicate alter table statement on temporary tables */
+    /*
+      We don't replicate alter table statement on temporary tables
+      For which we did not log the CREATE TEMPORARY TABLE statement.
+    */
     if (table->s->tmp_table == NO_TMP_TABLE ||
-        !thd->is_current_stmt_binlog_format_row())
+        table->s->table_creation_was_logged)
     {
       if (write_bin_log(thd, true, thd->query(), thd->query_length()))
         DBUG_RETURN(true);