MDEV-31177: SHOW SLAVE STATUS Last_SQL_Errno Race Condition on Errored Slave Restart
The SQL thread and a user connection executing SHOW SLAVE STATUS
have a race condition on Last_SQL_Errno, such that a slave which
previously errored and stopped, on its next start, SHOW SLAVE STATUS
can show that the SQL Thread is running while the previous error is
also showing.
The fix is to move when the last error is cleared when the SQL
thread starts to occur before setting the status of
Slave_SQL_Running.
Thanks to Kristian Nielson for his work diagnosing the problem!
MDEV-31813 SET GLOBAL innodb_max_purge_lag_wait hangs if innodb_read_only
innodb_max_purge_lag_wait_update(): Return immediately if we are
in high_level_read_only mode.
srv_wake_purge_thread_if_not_active(): Relax a debug assertion.
If srv_read_only_mode holds, purge_sys.enabled() will not hold
and this function will do nothing.
trx_t::commit_in_memory(): Remove a redundant condition before
invoking srv_wake_purge_thread_if_not_active().
Spider connection string is a comma-separated parameter definitions,
where each definition is of the form "<param_title> <param_value>",
where <param_value> is quote delimited on both ends, with backslashes
acting as an escaping prefix.
Despite the simple syntax, the existing spider connection string
parser was poorly-written, complex, hard to reason and error-prone,
causing issues like the one described in MDEV-31117. For example it
treated param title the same way as param value when assigning, and
have nonsensical fields like delim_title_len and delim_title.
Thus as part of the bugfix, we clean up the spider comment connection
string parsing, including:
- Factoring out some code from the parsing function
- Simplify the struct `st_spider_param_string_parse`
- And any necessary changes caused by the above changes
