MDEV-34014 mysql_upgrade failed

Adding a new statement into scripts/sys_schema/before_setup.sql:

  ALTER DATABASE sys CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci;

to fix db.opt in case:
- the database `sys` was altered to unexpected CHARACTER SET or COLLATE values
- or db.opt was erroneously removed

to make sure that sys objects are always recreated using utf8mb3_general_ci.

mysql-test/main/mysql_upgrade-34014.opt

+--character-set-server=utf8mb3
+--collation-server=utf8mb3_unicode_ci

mysql-test/main/mysql_upgrade-34014.result

+#
+# Stat of 10.6 tests
+#
+#
+# MDEV-34014 mysql_upgrade failed
+#
+SHOW CREATE DATABASE sys;
+Database	Create Database
+sys	CREATE DATABASE `sys` /*!40100 DEFAULT CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci */
+# Emulate db.opt file was removed in a mistake
+FLUSH TABLES;
+SHOW CREATE DATABASE sys;
+Database	Create Database
+sys	CREATE DATABASE `sys` /*!40100 DEFAULT CHARACTER SET utf8mb3 COLLATE utf8mb3_unicode_ci */
+Phase 1/8: Checking and upgrading mysql database
+Processing databases
+mysql
+mysql.column_stats                                 OK
+mysql.columns_priv                                 OK
+mysql.db                                           OK
+mysql.event                                        OK
+mysql.func                                         OK
+mysql.global_priv                                  OK
+mysql.gtid_slave_pos                               OK
+mysql.help_category                                OK
+mysql.help_keyword                                 OK
+mysql.help_relation                                OK
+mysql.help_topic                                   OK
+mysql.index_stats                                  OK
+mysql.innodb_index_stats
+Error    : Unknown storage engine 'InnoDB'
+error    : Corrupt
+mysql.innodb_table_stats
+Error    : Unknown storage engine 'InnoDB'
+error    : Corrupt
+mysql.plugin                                       OK
+mysql.proc                                         OK
+mysql.procs_priv                                   OK
+mysql.proxies_priv                                 OK
+mysql.roles_mapping                                OK
+mysql.servers                                      OK
+mysql.table_stats                                  OK
+mysql.tables_priv                                  OK
+mysql.time_zone                                    OK
+mysql.time_zone_leap_second                        OK
+mysql.time_zone_name                               OK
+mysql.time_zone_transition                         OK
+mysql.time_zone_transition_type                    OK
+mysql.transaction_registry
+Error    : Unknown storage engine 'InnoDB'
+error    : Corrupt
+
+Repairing tables
+mysql.innodb_index_stats
+Error    : Unknown storage engine 'InnoDB'
+error    : Corrupt
+mysql.innodb_table_stats
+Error    : Unknown storage engine 'InnoDB'
+error    : Corrupt
+mysql.transaction_registry
+Error    : Unknown storage engine 'InnoDB'
+error    : Corrupt
+Phase 2/8: Installing used storage engines... Skipped
+Phase 3/8: Running 'mysql_fix_privilege_tables'
+Phase 4/8: Fixing views
+mysql.user                                         OK
+sys.host_summary                                   OK
+sys.host_summary_by_file_io                        OK
+sys.host_summary_by_file_io_type                   OK
+sys.host_summary_by_stages                         OK
+sys.host_summary_by_statement_latency              OK
+sys.host_summary_by_statement_type                 OK
+sys.innodb_buffer_stats_by_schema                  OK
+sys.innodb_buffer_stats_by_table                   OK
+sys.innodb_lock_waits                              OK
+sys.io_by_thread_by_latency                        OK
+sys.io_global_by_file_by_bytes                     OK
+sys.io_global_by_file_by_latency                   OK
+sys.io_global_by_wait_by_bytes                     OK
+sys.io_global_by_wait_by_latency                   OK
+sys.latest_file_io                                 OK
+sys.memory_by_host_by_current_bytes                OK
+sys.memory_by_thread_by_current_bytes              OK
+sys.memory_by_user_by_current_bytes                OK
+sys.memory_global_by_current_bytes                 OK
+sys.memory_global_total                            OK
+sys.metrics                                        OK
+sys.processlist                                    OK
+sys.ps_check_lost_instrumentation                  OK
+sys.schema_auto_increment_columns                  OK
+sys.schema_index_statistics                        OK
+sys.schema_object_overview                         OK
+sys.schema_redundant_indexes                       OK
+sys.schema_table_lock_waits                        OK
+sys.schema_table_statistics                        OK
+sys.schema_table_statistics_with_buffer            OK
+sys.schema_tables_with_full_table_scans            OK
+sys.schema_unused_indexes                          OK
+sys.session                                        OK
+sys.session_ssl_status                             OK
+sys.statement_analysis                             OK
+sys.statements_with_errors_or_warnings             OK
+sys.statements_with_full_table_scans               OK
+sys.statements_with_runtimes_in_95th_percentile    OK
+sys.statements_with_sorting                        OK
+sys.statements_with_temp_tables                    OK
+sys.user_summary                                   OK
+sys.user_summary_by_file_io                        OK
+sys.user_summary_by_file_io_type                   OK
+sys.user_summary_by_stages                         OK
+sys.user_summary_by_statement_latency              OK
+sys.user_summary_by_statement_type                 OK
+sys.version                                        OK
+sys.wait_classes_global_by_avg_latency             OK
+sys.wait_classes_global_by_latency                 OK
+sys.waits_by_host_by_latency                       OK
+sys.waits_by_user_by_latency                       OK
+sys.waits_global_by_latency                        OK
+sys.x$host_summary                                 OK
+sys.x$host_summary_by_file_io                      OK
+sys.x$host_summary_by_file_io_type                 OK
+sys.x$host_summary_by_stages                       OK
+sys.x$host_summary_by_statement_latency            OK
+sys.x$host_summary_by_statement_type               OK
+sys.x$innodb_buffer_stats_by_schema                OK
+sys.x$innodb_buffer_stats_by_table                 OK
+sys.x$innodb_lock_waits                            OK
+sys.x$io_by_thread_by_latency                      OK
+sys.x$io_global_by_file_by_bytes                   OK
+sys.x$io_global_by_file_by_latency                 OK
+sys.x$io_global_by_wait_by_bytes                   OK
+sys.x$io_global_by_wait_by_latency                 OK
+sys.x$latest_file_io                               OK
+sys.x$memory_by_host_by_current_bytes              OK
+sys.x$memory_by_thread_by_current_bytes            OK
+sys.x$memory_by_user_by_current_bytes              OK
+sys.x$memory_global_by_current_bytes               OK
+sys.x$memory_global_total                          OK
+sys.x$processlist                                  OK
+sys.x$ps_digest_95th_percentile_by_avg_us          OK
+sys.x$ps_digest_avg_latency_distribution           OK
+sys.x$ps_schema_table_statistics_io                OK
+sys.x$schema_flattened_keys                        OK
+sys.x$schema_index_statistics                      OK
+sys.x$schema_table_lock_waits                      OK
+sys.x$schema_table_statistics                      OK
+sys.x$schema_table_statistics_with_buffer          OK
+sys.x$schema_tables_with_full_table_scans          OK
+sys.x$session                                      OK
+sys.x$statement_analysis                           OK
+sys.x$statements_with_errors_or_warnings           OK
+sys.x$statements_with_full_table_scans             OK
+sys.x$statements_with_runtimes_in_95th_percentile  OK
+sys.x$statements_with_sorting                      OK
+sys.x$statements_with_temp_tables                  OK
+sys.x$user_summary                                 OK
+sys.x$user_summary_by_file_io                      OK
+sys.x$user_summary_by_file_io_type                 OK
+sys.x$user_summary_by_stages                       OK
+sys.x$user_summary_by_statement_latency            OK
+sys.x$user_summary_by_statement_type               OK
+sys.x$wait_classes_global_by_avg_latency           OK
+sys.x$wait_classes_global_by_latency               OK
+sys.x$waits_by_host_by_latency                     OK
+sys.x$waits_by_user_by_latency                     OK
+sys.x$waits_global_by_latency                      OK
+Phase 5/8: Fixing table and database names
+Phase 6/8: Checking and upgrading tables
+Processing databases
+information_schema
+mtr
+mtr.global_suppressions                            OK
+mtr.test_suppressions                              OK
+performance_schema
+sys
+sys.sys_config                                     OK
+test
+Phase 7/8: uninstalling plugins
+Phase 8/8: Running 'FLUSH PRIVILEGES'
+OK
+SHOW CREATE DATABASE sys;
+Database	Create Database
+sys	CREATE DATABASE `sys` /*!40100 DEFAULT CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci */
+#
+# End of 10.6 tests
+#

mysql-test/main/mysql_upgrade-34014.test

+--source include/mysql_upgrade_preparation.inc
+
+let $MYSQLD_DATADIR= `select @@datadir`;
+
+--echo #
+--echo # Stat of 10.6 tests
+--echo #
+
+--echo #
+--echo # MDEV-34014 mysql_upgrade failed
+--echo #
+
+SHOW CREATE DATABASE sys;
+
+--echo # Emulate db.opt file was removed in a mistake
+--remove_file $MYSQLD_DATADIR/sys/db.opt
+FLUSH TABLES;
+SHOW CREATE DATABASE sys;
+
+--exec $MYSQL_UPGRADE --force 2>&1
+--remove_file $MYSQLD_DATADIR/mysql_upgrade_info
+SHOW CREATE DATABASE sys;
+
+--echo #
+--echo # End of 10.6 tests
+--echo #

scripts/sys_schema/before_setup.sql

@@ -17,6 +17,11 @@ SET NAMES utf8;
 SET @sql_log_bin = @@sql_log_bin;
 SET sql_log_bin = 0;
 
-CREATE DATABASE IF NOT EXISTS sys DEFAULT CHARACTER SET utf8;
+CREATE DATABASE IF NOT EXISTS sys DEFAULT CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci;
+
+-- If the database had existed, let's recreate its db.opt:
+-- * to fix it if it contained unexpected charset/collation values
+-- * to create it if it was removed in a mistake
+ALTER DATABASE sys CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci;
 
 USE sys;