MDEV-21244 mysql_upgrade creating empty global_priv table

support upgrades from 5.2 privilege tables

mysql-test/main/mysql_upgrade.result

@@ -630,4 +630,12 @@ drop table mysql.innodb_index_stats, mysql.innodb_table_stats;
 # mysql_upgrade --force --silent 2>&1
 drop table mysql.global_priv;
 rename table mysql.global_priv_bak to mysql.global_priv;
+drop view mysql.user_bak;
+alter table mysql.user change authentication_string auth_string text collate utf8_bin not null;
+# mysql_upgrade --force --silent 2>&1
+select count(*) from mysql.global_priv;
+count(*)
+4
+drop table mysql.global_priv;
+rename table mysql.global_priv_bak to mysql.global_priv;
 # End of 10.4 tests

mysql-test/main/mysql_upgrade.test

@@ -282,4 +282,17 @@ drop table mysql.innodb_index_stats, mysql.innodb_table_stats;
 drop table mysql.global_priv;
 rename table mysql.global_priv_bak to mysql.global_priv;
 
+#
+# MDEV-21244 mysql_upgrade creating empty global_priv table
+#
+--source include/switch_to_mysql_user.inc
+drop view mysql.user_bak;
+alter table mysql.user change authentication_string auth_string text collate utf8_bin not null;
+--echo # mysql_upgrade --force --silent 2>&1
+--exec $MYSQL_UPGRADE --force --silent 2>&1
+--remove_file $MYSQLD_DATADIR/mysql_upgrade_info
+select count(*) from mysql.global_priv;
+drop table mysql.global_priv;
+rename table mysql.global_priv_bak to mysql.global_priv;
+
 --echo # End of 10.4 tests

scripts/mysql_system_tables_fix.sql

@@ -648,6 +648,7 @@ UPDATE user SET Delete_history_priv = Super_priv WHERE @had_user_delete_history_
 
 ALTER TABLE user ADD plugin char(64) CHARACTER SET latin1 DEFAULT '' NOT NULL,
                  ADD authentication_string TEXT NOT NULL;
+ALTER TABLE user CHANGE auth_string authentication_string TEXT NOT NULL;
 ALTER TABLE user MODIFY plugin char(64) CHARACTER SET latin1 DEFAULT '' NOT NULL,
                  MODIFY authentication_string TEXT NOT NULL;
 ALTER TABLE user ADD password_expired ENUM('N', 'Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL;