MDEV-16952 Introduce SET GLOBAL innodb_max_purge_lag_wait

Let us introduce a dummy variable innodb_max_purge_lag_wait for waiting that the InnoDB history list length is below the user-specified limit. Specifically, SET GLOBAL innodb_max_purge_lag_wait=0; should wait for all history to be purged. This could be useful when upgrading from an older version to MariaDB 10.3 or later, to avoid hitting MDEV-15912. Note: the history cannot be purged if there exist transactions that may see old versions. Reviewed by: Vladislav Vaintroub

Author: dr-m

mysql-test/suite/innodb/include/wait_all_purged.inc

@@ -1,25 +1,17 @@
 # Wait for everything to be purged.
 # The user should have set innodb_purge_rseg_truncate_frequency=1.
 
+--disable_query_log
 if (!$wait_all_purged)
 {
- let $wait_all_purged= 0;
+ SET GLOBAL innodb_max_purge_lag_wait= 0;
 }
-let $remaining_expect= `select concat('InnoDB	',$wait_all_purged)`;
-
-let $wait_counter= 600;
-while ($wait_counter)
+if ($wait_all_purged)
 {
- --replace_regex /.*History list length ([0-9]+).*/\1/
- let $remaining= `SHOW ENGINE INNODB STATUS`;
- if ($remaining == $remaining_expect)
- {
- let $wait_counter= 0;
- }
- if ($wait_counter)
- {
- real_sleep 0.1;
- dec $wait_counter;
- }
+ eval SET GLOBAL innodb_max_purge_lag_wait= $wait_all_purged;
 }
+--enable_query_log
+
+--replace_regex /.*History list length ([0-9]+).*/\1/
+let $remaining= `SHOW ENGINE INNODB STATUS`;
 echo $remaining transactions not purged;

mysql-test/suite/sys_vars/r/sysvars_innodb.result

@@ -1686,6 +1686,18 @@ NUMERIC_BLOCK_SIZE	0
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
+VARIABLE_NAME	INNODB_MAX_PURGE_LAG_WAIT
+SESSION_VALUE	NULL
+DEFAULT_VALUE	4294967295
+VARIABLE_SCOPE	GLOBAL
+VARIABLE_TYPE	INT UNSIGNED
+VARIABLE_COMMENT	Wait until History list length is below the specified limit
+NUMERIC_MIN_VALUE	0
+NUMERIC_MAX_VALUE	4294967295
+NUMERIC_BLOCK_SIZE	0
+ENUM_VALUE_LIST	NULL
+READ_ONLY	NO
+COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	INNODB_MAX_UNDO_LOG_SIZE
 SESSION_VALUE	NULL
 DEFAULT_VALUE	10485760

storage/innobase/handler/ha_innodb.cc

@@ -271,6 +271,27 @@ enum default_row_format_enum {
 DEFAULT_ROW_FORMAT_DYNAMIC = 2,
 };
 
+/** A dummy variable */
+static uint innodb_max_purge_lag_wait;
+
+/** Wait for trx_sys_t::rseg_history_len to be below a limit. */
+static void innodb_max_purge_lag_wait_update(THD *thd, st_mysql_sys_var *,
+ void *, const void *limit)
+{
+ const uint l= *static_cast<const uint*>(limit);
+ if (trx_sys->rseg_history_len <= l)
+ return;
+ mysql_mutex_unlock(&LOCK_global_system_variables);
+ while (trx_sys->rseg_history_len > l)
+ {
+ if (thd_kill_level(thd))
+ break;
+ srv_wake_purge_thread_if_not_active();
+ os_thread_sleep(100000);
+ }
+ mysql_mutex_lock(&LOCK_global_system_variables);
+}
+
 static
 void set_my_errno(int err)
 {
@@ -20147,6 +20168,11 @@ static MYSQL_SYSVAR_ULONG(max_purge_lag_delay, srv_max_purge_lag_delay,
  0L,	/* Minimum value */
  10000000UL, 0);	/* Maximum value */
 
+static MYSQL_SYSVAR_UINT(max_purge_lag_wait, innodb_max_purge_lag_wait,
+ PLUGIN_VAR_RQCMDARG,
+ "Wait until History list length is below the specified limit",
+ NULL, innodb_max_purge_lag_wait_update, UINT_MAX, 0, UINT_MAX, 0);
+
 static MYSQL_SYSVAR_BOOL(rollback_on_timeout, innobase_rollback_on_timeout,
  PLUGIN_VAR_OPCMDARG | PLUGIN_VAR_READONLY,
  "Roll back the complete transaction on lock wait timeout, for 4.x compatibility (disabled by default)",
@@ -21195,6 +21221,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
  MYSQL_SYSVAR(flushing_avg_loops),
  MYSQL_SYSVAR(max_purge_lag),
  MYSQL_SYSVAR(max_purge_lag_delay),
+ MYSQL_SYSVAR(max_purge_lag_wait),
  MYSQL_SYSVAR(old_blocks_pct),
  MYSQL_SYSVAR(old_blocks_time),
  MYSQL_SYSVAR(open_files),