Type_handler_xxx::Item_const_eq() can handle only non-NULL values.
The code in Item_basic_value::eq() did not take this into account.

Adding a test to detect three different combinations:
- Both values are NULLs, return true.
- Only one value is NULL, return false.
- Both values are not NULL, call Type_handler::Item_const_eq()
  to check equality.

Flush LSN to system tablespace on innodb shutdown if XA is rolled back by
mariabackup.

innobase_get_charset(), innobase_get_stmt_safe(): Remove.
It is more efficient and readable to invoke thd_charset()
and thd_query_safe() directly, without a non-inlined wrapper function.

The function thd_query_safe() is used in the implementation of the
following INFORMATION_SCHEMA views:

    information_schema.innodb_trx
    information_schema.innodb_locks
    information_schema.innodb_lock_waits
    information_schema.rocksdb_trx

The implementation of the InnoDB views is in trx_i_s_common_fill_table().
This function invokes trx_i_s_possibly_fetch_data_into_cache(),
which will acquire lock_sys->mutex and trx_sys->mutex in order to
protect the set of active transactions and explicit locks.
While holding those mutexes, it will traverse the collection of
InnoDB transactions. For each transaction, thd_query_safe() will be
invoked.

When called via trx_i_s_common_fill_table(), thd_query_safe()
is acquiring THD::LOCK_thd_data while holding the InnoDB locks.
This will cause a deadlock with THD::awake() (such as executing
KILL QUERY), because THD::awake() could invoke lock_trx_handle_wait(),
which attempts to acquire lock_sys->mutex while already holding
THD::lock_thd_data.

thd_query_safe(): Invoke mysql_mutex_trylock() instead of
mysql_mutex_lock(). Return the empty string if the mutex
cannot be acquired without waiting.

Not only Ubuntu Focal builds openssl with OPENSSL_TLS_SECURITY_LEVEL=2,
but for some unfathomable reason it patches openssl sources to disable
TLS < 1.2 at security level 2, even though openssl manual says it
should only happen at level 4:
https://www.openssl.org/docs/man1.1.0/man3/SSL_CTX_set_security_level.html

We test TLSv1.1 and TLSv1, so we have to override Focal defaults in mtr.

As part of the SPATIAL INDEX implementation in InnoDB,
dict_index_t was expanded by a rtr_ssn_t field. There are only
3 operations for this field, all protected by rtr_ssn_t::mutex:

* btr_cur_search_to_nth_level() stores the least significant 32 bits
of the 64-bit value that is stored in the index root page.
(This would better be done when the table is opened for the
very first time.)
* rtr_get_new_ssn_id() increments the value by 1.
* rtr_get_current_ssn_id() reads the current value.

All these operations can be implemented equally safely by using
atomic memory access operations.

setup alternative name for rhel8/centos8

use correct C/C version when providing mariadb-connector-c
and other changes for installation over distro packages to work:

  dnf install mariadb-server
  dnf install --allowerasing MariaDB-{server,common,client,shared}*.rpm

The code did not take into account that:
- U+005C (backslash) can occupy more than mbminlen characters (e.g. in sjis)
- Some character sets do not have a code for U+005C (e.g. swe7)

Adding a new function my_wc_to_printable into MY_CHARSET_HANDLER to
cover all special cases easier.

The titlebar scrambled var/log/Stdout.log and can becasue of this not be
on by default.

MDEV-22488 test failures: parts.partition_debug_innodb /
           parts.partition_debug_myisam

The reason for the failure was a wrong printf() that accessed not existing
things on the stack.
The reason the falure was hard to find was that the partition_debug_...
tests disables core dumps, so there was no trace that the server had
crashed in the logs.

Fixed by fixing the faulty push_warning_printf() and splitting the tests
into two parts, one that test failures (with core dumps enabled) and one
part that test crash recovery.

The review and test splitting was done by Monty

In commit ea37b144
we removed the MDEV-16222 test case but forgot to remove
the debug instrumentation.

correct the help text

When we move data we should fix buffer string length

remove Timeval workaround (not needed anymore).
add template workaround.
comments.

Let us limit the maximum value of the debug parameter
innodb_data_file_size to 256 MiB. It is only being used
in the test innodb.log_data_file_size, and the size
of the system tablespace should never exceed some 70 MiB
in ./mtr. Thus, 256 MiB should be a reasonable limit.

The fact that negative values that are passed to unsigned parameters
wrap around to the maximum value appears to be a regression due to
commit 18ef02b0
and has been filed as bug MDEV-22219.