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

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.

Fix WolfSSL build:

- Do not build with TLSv1.0,it stopped working,at least with SChannel client
- Disable a test that depends on TLSv1.0
- define FP_MAX_BITS always, to fix 32bit builds.
- Increase MAX_AES_CTX_SIZE, to fix build on Linux

Enable tests with additional galera output to find out actual
reason for test failures.

under LOCK TABLES we still have to open everything, otherwise DML
prelocking will try to take an MDL on a table that wasn't in the
LOCK TABLES list.

MDEV-21421 : Galera test sporadic failure on galera.galera_as_slave_gtid_myisam: Result length mismatch

Add wait_condition so that drop table has time to replicate to
Galera cluster.

MDEV-21421 : Galera test sporadic failure on galera.galera_as_slave_gtid_myisam: Result length mismatch

Add wait_condition so that drop table has time to replicate to
Galera cluster.

The test was incompatible with ./mtr --repeat=2 until
commit 2d6719d7
fixed that.

It turns out that the failing assertion that we disabled in
commit 3db94d24
is bogus and can fail when the change buffer is emptied
during the last batch of crash recovery. The reason for this
is the condition around the page_create_empty() call in
page_cur_delete_rec(). The condition was removed in MariaDB
Server 10.5 as part of MDEV-12353, in
commit 7ae21b18 and
commit f8a9f906.

The bug that the assertion aimed to catch is MDEV-22497, which
was fixed in commit 26aab96e.

The InnoDB insert buffer was upgraded in MySQL 5.5 into a change
buffer that also covers delete-mark and delete (purge) operations.

There is an important constraint for delete operations: a B-tree
leaf page must not become empty unless the entire tree becomes empty,
consisting of an empty root page. Because change buffer merges only
occur on a single leaf page at a time, delete operations must not be
buffered if it is possible that the last record of the page could be
deleted. (In that case, we would refuse to use the change buffer, and
if we really delete the last record, we would shrink the index tree.)

The function ibuf_get_volume_buffered_hash() is part of our insurance
that the page would not become empty. It is supposed to map each
buffered INSERT or DELETE_MARK record payload into a hash value.
We will only count each such record as a distinct key if there is no
hash collision. DELETE operations will always decrement the predicted
number fo records in the page.

Due to a bug in the function, we would actually compute the hash value
not only on the record payload, but also on some following bytes,
in case the record contains NULL values. In MySQL Bug #61104, we had
some examples of this dating back to 2012. But back then, we failed to
reproduce the bug, and in commit d84c9557
we simply demoted the hard assertion to a message printout and a debug
assertion failure.

ibuf_get_volume_buffered_hash(): Correctly compute the hash value
of the payload bytes only. Note: we will consider
('foo','bar'),(NULL,'foobar'),('foob','ar') to be equal, but this
is not a problem, because in case of a hash collision, we could
also consider ('boo','far') to be equal, and underestimate the number
of records in the page, leading to refusing to buffer a DELETE.