The fix of MDEV-23456 (commit b1009ae5)
introduced a livelock between page flushing and a thread that is
executing buf_page_create().

buf_page_create(): If the current mini-transaction is holding
an exclusive latch on the page, do not attempt to acquire another
one, and do not care about any I/O fix.

mtr_t::have_x_latch(): Replaces mtr_t::get_fix_count().

dyn_buf_t::for_each_block(const Functor&) const: A new variant.

rw_lock_own(): Add a const qualifier.

Reviewed by: Thirunarayanan Balathandayuthapani

Due to a premature cleanup of the unit that specified a recursive CTE
used in the second operand of union the server fell into an infinite
loop in the reported test case. In other cases this premature cleanup
could cause other problems.
The bug is the result of a not quite correct fix for MDEV-17024. The
unit that specifies a recursive CTE has to be cleaned only after the
cleanup of the last external reference to this CTE. It means that
cleanups of the unit triggered not by the cleanup of a external
reference to the CTE must be blocked.
Usage of local table chains in selects to get external references to
recursive CTEs was not correct either because of possible merges of
some selects.

Also fixed a minor bug in st_select_lex::set_explain_type() that caused
typing 'RECURSIVE UNION' instead of 'UNION' in EXPLAIN output for external
references to a recursive CTE.

Analysis:
========
Writes to 'rli->log_space_total' needs to be synchronized, otherwise both
SQL_THREAD and IO_THREAD can try to modify the variable simultaneously
resulting in incorrect rli->log_space_total.  In the current test scenario
SQL_THREAD is trying to decrement 'rli->log_space_total' in 'purge_first_log'
and IO_THREAD is trying to increment the 'rli->log_space_total' in
'queue_event' simultaneously. Hence test occasionally fails with  result
mismatch.

Fix:
===
Convert 'rli->log_space_total' variable to atomic type.

As noted in commit 0b66d3f7,
MariaDB does not support CREATE TABLESPACE for InnoDB.
Hence, some code that was added in
commit fec844ac
and originally in
mysql/mysql-server@c71dd213bd434c0579e454ab8880e6d3756b0fb0
is unused in MariaDB and should be removed.

trx_undo_left(): Return 0 in case of an overflow, instead of
returning a negative number interpreted as a large positive number.
Also, add debug assertions to check that the pointer is within
the page area. This should allow us to catch bugs like
MDEV-24096 easier in the future.

The function ibuf_merge_or_delete_for_page() was always being
invoked with update_ibuf_bitmap=true ever since
commit cd623508
fixed up something after MDEV-9566.

Furthermore, the parameter page_size is never being passed as a
null pointer, and therefore it should better be a reference to
a constant object.

- Patch 95bb3cb8 used `my_which` function in `10.2`
- Based on patch `355ee687` from 10.3+ `command -v` is used instead of
`my_which` so we are changing in this patch also
- `ldconfig` is usually found in `/sbin` so make sure it is added in
`$PATH` variable

- Patch is solving generating report on warning
        To repeat the error run single worker:
        ```
        ./mtr --mysqld=--lock-wait-timeout=-xx 1st 1st --force --parallel 1
        ```
        or `N` workers with `N+1` tests with failures and `force`
        ```
        ./mtr --mysqld=--lock-wait-timeout=-xx 1st 1st grant5 --force --parallel 2
        ```
- Patch is doing cosmetic fix of `current_test` log file which holds the old log value of test `CURRENT TEST:..` in `mark_log()` in case of `unknown option` and as such
  the logic which is using it's content doesn't output valid log content and doesn't generate valid `$test->{'comment'}` message.asdf

- Closing the socket/handler after the removing the handler from IO for
consistency

Reviewed by: serg@mariadb.com

Adjust the testcase for MariaDB 10.3+ : prevent IN-to-subquery conversion
optimization from working.

The row_log_t::mutex is a mutex, yet it was instrumented as
rw-lock in PERFORMANCE_SCHEMA.

This bug could manifest itself for a query with WHERE condition containing
top level OR formula such that each conjunct contained a single-range
condition supported by the same index. One of these range conditions must
be fully covered by another range condition that is used later in the OR
formula. Additionally at least one of these condition should be ANDed with
a sargable range condition supported by a different index.

There were several attempts to fix related problems for OR conditions after
the backport of range optimizer code from MySQL (commit
0e19f3e3). Unfortunately the first of these
fixes contained typo remained unnoticed until recently. This typo bug led
to rejection of valid range accesses. This patch fixed this typo bug.
The fix revealed another two bugs: one in a constructor for SEL_ARG,
the other in the function tree_or(). Both are fixed in this patch.

Add a testcase.

Part#1: Revert the patch that caused it:

commit 291be494
Author: Igor Babaev <igor@askmonty.org>
Date:   Thu Sep 24 22:02:00 2020 -0700

    MDEV-23811: With large number of indexes optimizer chooses an inefficient plan

The instrumentation that was added in
commit 90635c6f (MDEV-7620)
was effectively reverted in MariaDB Server 10.2.2, in
commit 2e814d47
(which stopped reporting the statistics) and
commit fec844ac
(which stopped updating the statistics).

Let us remove the orphan data members to reduce the memory footprint.

- mysqlnd from PHP < 7.3
- mysql-connector-python any version
- mysql-connector-java any version

Relaxed check about garbage at the end of the packet in case of no parameters.
Added check for array binding.
Fixed test according to the new paradigm (allow junk at the end of the packet)

Changed the test so that it does not rely on specific auto increment
ids. With Galera's default wsrep_auto_increment_control setting it is
not guaranteed that auto increments always start from 1. The test was
occasionally failing due to result content mismatch.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

Bugs fixed:
- prepare_for_repair() didn't close all open files if table opened failed
  because of out-of-memory
- If dd_recreate_table() failed, the data file was not properly restored
  from it's temporary name
- Aria repair initializing code didn't properly clear all used structs
  before calling error, which caused crashed in memory-free calls.
- maria_delete_table() didn't register if table open failed. This could
  calls my_error() to be called without returning 1 to the caller, which
  cased failures in my_ok()

Note when merging to 10.5:
- Remove the #if MYSQL_VERSION from sql_admin.cc

C++11 is allowed only starting with MariaDB Server 10.4.

This follows up commit
commit 94a520dd and
commit 7c5519c1.

After these changes, the default test suites on a
cmake -DWITH_UBSAN=ON build no longer fail due to passing
null pointers as parameters that are declared to never be null,
but plenty of other runtime errors remain.