BUG#30311908 RESTARTING SERVER POST 'RESET SLAVE', CLEANS UP SLAVE_RELAY_LOG_INFO SETTINGS

Description
-----------
While implementing WL#12966 and WL#12968, decision was made to not clear
`PRIVILEGE_CHECKS_USER` and `REQUIRES_ROW_FORMAT` options values when performing
a `RESET SLAVE`. The state of such options is not kept if after a `RESET SLAVE`
the server is restarted.

Analysis
--------
Although the option values are kept in memory after a `RESET SLAVE`, the same
values are not persisted into the configured repository in order to be reloaded
into memory after a server restart.

Fix
---
1) Make `Relay_log_info` fields nullable.
2) Make `RESET SLAVE` clear all field values except for `PRIVILEGE_CHECKS_USER`
   and `REQUIRE_ROW_FORMAT`.
3) Persist the cleared record into the relay-log repositories.
4) Change boot logic so that the cleared record is used to instantiate
   `PRIVILEGE_CHECKS_USER` and `REQUIRE_ROW_FORMAT` and then relay log is
   initialized as before.

RB: 23376
Reviewed-by: Pedro Gomes <pedro.gomes@oracle.com>
Reviewed-by: Luís Soares <luis.soares@oracle.com>

Author: Pedro Figueiredo

mysql-test/include/rpl_end.inc

@@ -206,13 +206,22 @@ while ($_rpl_server)
     --enable_query_log
   }
 
-  # Drop created privileged database
+  # Restore state for PRIVILEGE_CHECKS_USER
   if ($rpl_privilege_checks_user)
   {
     --disable_query_log
     SET @@sql_log_bin = 0;
+    # Drop created privileged database
     DROP DATABASE rpl_priv;
     SET @@sql_log_bin = 1;
+    CHANGE MASTER TO PRIVILEGE_CHECKS_USER=NULL;
+    --enable_query_log
+  }
+  # Restore state for REQUIRE_ROW_FORMAT
+  if ($rpl_require_row_format)
+  {
+    --disable_query_log
+    CHANGE MASTER TO REQUIRE_ROW_FORMAT=0;
     --enable_query_log
   }
 

mysql-test/include/rpl_reset_slave_helper.inc

@@ -5,10 +5,26 @@ if (!$rpl_reset_slave_all)
 {
   if (!$rpl_multi_source)
   {
+    if ($rpl_privilege_checks_user)
+    {
+      CHANGE MASTER TO PRIVILEGE_CHECKS_USER=NULL;
+    }
+    if ($rpl_require_row_format)
+    {
+      CHANGE MASTER TO REQUIRE_ROW_FORMAT=0;
+    }
     RESET SLAVE;
   }
   if ($rpl_multi_source)
   {
+    if ($rpl_privilege_checks_user)
+    {
+      eval CHANGE MASTER TO PRIVILEGE_CHECKS_USER=NULL FOR CHANNEL $rpl_channel_name;
+    }
+    if ($rpl_require_row_format)
+    {
+      eval CHANGE MASTER TO REQUIRE_ROW_FORMAT=0 FOR CHANNEL $rpl_channel_name;
+    }
     eval RESET SLAVE FOR CHANNEL $rpl_channel_name;
   }
 }
@@ -24,4 +40,3 @@ if ($rpl_reset_slave_all)
     eval RESET SLAVE ALL FOR CHANNEL $rpl_channel_name;
   }
 }
-

mysql-test/r/mysqldump.result

@@ -5334,13 +5334,13 @@ CREATE TABLE IF NOT EXISTS `slave_master_info` (
 /*!50503 SET character_set_client = utf8mb4 */;
 CREATE TABLE IF NOT EXISTS `slave_relay_log_info` (
   `Number_of_lines` int unsigned NOT NULL COMMENT 'Number of lines in the file or rows in the table. Used to version table definitions.',
-  `Relay_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL COMMENT 'The name of the current relay log file.',
-  `Relay_log_pos` bigint unsigned NOT NULL COMMENT 'The relay log position of the last executed event.',
-  `Master_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL COMMENT 'The name of the master binary log file from which the events in the relay log file were read.',
-  `Master_log_pos` bigint unsigned NOT NULL COMMENT 'The master log position of the last executed event.',
-  `Sql_delay` int NOT NULL COMMENT 'The number of seconds that the slave must lag behind the master.',
-  `Number_of_workers` int unsigned NOT NULL,
-  `Id` int unsigned NOT NULL COMMENT 'Internal Id that uniquely identifies this record.',
+  `Relay_log_name` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The name of the current relay log file.',
+  `Relay_log_pos` bigint unsigned DEFAULT NULL COMMENT 'The relay log position of the last executed event.',
+  `Master_log_name` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The name of the master binary log file from which the events in the relay log file were read.',
+  `Master_log_pos` bigint unsigned DEFAULT NULL COMMENT 'The master log position of the last executed event.',
+  `Sql_delay` int DEFAULT NULL COMMENT 'The number of seconds that the slave must lag behind the master.',
+  `Number_of_workers` int unsigned DEFAULT NULL,
+  `Id` int unsigned DEFAULT NULL COMMENT 'Internal Id that uniquely identifies this record.',
   `Channel_name` char(64) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT 'The channel on which the slave is connected to a source. Used in Multisource Replication',
   `Privilege_checks_username` char(32) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL COMMENT 'Username part of PRIVILEGE_CHECKS_USER.',
   `Privilege_checks_hostname` char(255) CHARACTER SET ascii COLLATE ascii_general_ci DEFAULT NULL COMMENT 'Hostname part of PRIVILEGE_CHECKS_USER.',