This is the race between DELETE and INSERT (or other any two operations accessing to the table).
What should happen in good case:
1. ALTER TABLE is issued. vc_templ->default_rec is initialized with temporary share's default_fields
2. temporary share is freed, but datadict is still there, with garbage in vc_templ->default_rec
3. DELETE is issued. It is first after ALTER TABLE finished.
4. ha_innobase::open() is called, ib_table->get_ref_count() should be one
5. we reinitialize vc_templ, so no garbage anymore

What actually happens:
3. DELETE is issued.
4. ha_innobase::open() is called and ib_table->get_ref_count() is 1
5. INSERT (or SELECT etc.) is issued in parallel
6. ha_innobase::open() is called and ib_table->get_ref_count() is 1
7. we check ib_table->get_ref_count()  and it is 2 in both threads when we want reinitialize vc_templ
8. garbage is there

Fix:
* Do not store pointers to SHARE memory in table dict, copy it instead.
* But then we don't need to refresh it each time when refcount=1.

The test for the wsrep_info plugin needs the same flexible wsrep version checking as the tests for Galera (continuation of MDEV-18565 task)

Make it to work on Windows, too.

Rewrite the unportable sed/shell code in Perl.

Store REDZONE_SIZE poined bytes before every allocated chunk of memory

The embedded server does not HAVE_PSI_STAGE_INTERFACE.

row_merge_read_clustered_index(): fix one more place with buf and merge_buf[i]

The results are nondeterministic on MariaDB Server 10.1.

row_merge_read_clustered_index(): make buf always equals to merge_buf[i]

MDEV-20094 was filed for the unexpected result differences for the test
innodb.check_ibd_filesize.

Set the garbd_exe variable to empty string to avoid warning about an uninitialized variable when wsrep_provider is not initialized correctly, set to 'none' or when wsrep is switched off

Currently, running mtr with an incorrect (for example, new or
obsolete) version of wsrep_provider (for example, with the 26
version of libgalera_smm.so) leads to the failure of tests in
several suites with vague error diagnostics.

As for the galera_3nodes suite, the mtr also does not effectively
check all the prerequisites after merge with MDEV-18426 fixes.
For example, tests that using mariabackup do not check for presence
of ss and socat/nc. This is due to improper handling of relative
paths in mtr scripts.

In addition, some tests in different suites can be run without
setting the environment variables such as MTR_GALERA_TFMT, XBSTREAM,
and so on.

To eliminate all these issues, this patch makes the following changes:

1. Added auxiliary wsrep_mtr_check utility (which located in the
mysql-test/lib/My/SafeProcess subdirectory), which compares the
versions of the wsrep API that used by the server and by the wsrep
provider library, and it does this comparison safely, without
accessing the API if the versions do not match.

2. All checks related to the presence of mariabackup and utilities
that necessary for its operation transferred from the local directories
of different mtr suites (from the suite.pm files) to the main suite.pm
file. This not only reduces the amount of code and eliminates duplication
of identical code fragments, but also avoids problems due to the inability
of mtr to consider relative paths to include files when checking skip
combinations.

3. Setting the values of auxiliary environment variables that
are necessary for Galera, SST scripts and mariabackup (to work
properly) is moved to the main mysql-test-run.pl script, so as
not to duplicate this code in different suites, and to avoid
partial corrections of the same errors for different suites
(while other suites remain uncorrected).

4. Fixed duplication of the have_file_key_management.inc and
have_filekeymanagement.inc files between different suites,
these checks are also transferred to the top level.

5. Added garbd presence check and garbd path variable.

https://jira.mariadb.org/browse/MDEV-18565

It uses slave_gtid_info=optimized which is not supported in MariaDB

It requires @@enable_blind_replace which MariaDB doesn't support

It requires slave_exec_mode='SEMI_STRICT'

Fix this patch (two csets before):
  Disable rocksdb.shutdown test

  It was introduced by this patch in fb/mysql-5.6:
  Author: Yoshinori Matsunobu <yoshinori@fb.com>
  Date:   Mon Jun 10 14:09:28 2019 -0700

      Extending SHUTDOWN query to support read_only/aborting

      Summary:
      This diff extends SHUTDOWN query to support the following
      features.
      - Aborting with any specified exit code (range is 0..255).
      If nothing is specified or 0 is given, it does default clean
      shutdown. If 1+ is given, exits with the given error code
      immediately. This is helpful to shutting down instance
      even if it is stuck somewhere.

   MariaDB doesn't support SHUTDOWN statement or have any other way
   to exit the server process.

Part #2: also replace error text in SHOW WARNINGS

It was introduced by this patch in fb/mysql-5.6:
Author: Yoshinori Matsunobu <yoshinori@fb.com>
Date:   Mon Jun 10 14:09:28 2019 -0700

    Extending SHUTDOWN query to support read_only/aborting

    Summary:
    This diff extends SHUTDOWN query to support the following
    features.
    - Aborting with any specified exit code (range is 0..255).
    If nothing is specified or 0 is given, it does default clean
    shutdown. If 1+ is given, exits with the given error code
    immediately. This is helpful to shutting down instance
    even if it is stuck somewhere.

MariaDB doesn't support SHUTDOWN statement or have any other way
to exit the server process.

MDEV-11154: Write_on_release_cache(log_event.cc) function will not write "COMMIT", if use "mysqlbinlog ... | mysql ..."

Problem:
=======
Executing command, "mysqlbinlog --read-from-remote-server --host='xx.xx.xx.xx'
--port=3306 --user=xxx --password=xxx --database=mysql --to-last-log
mysql-bin.000001 --start-position=1098699 --stop-never |mysql -uxxx -pxxx", we
found that last data read from remote couldn't commit.

Analysis:
========
The purpose of 'Write_on_release_cache' is that the contents of the Cache will
automatically be written to a dedicated result file on destruction. Flush
operation on the result file is controlled by a flag 'FLUSH_F'. Events which
require force flush upon their destruction will have to enable this
'Write_on_release_cache::FLUSH_F'. At present the 'FLUSH_F' flag is defined as
an enum as shown below.

enum flag
{
  FLUSH_F
};

Since 'FLUSH_F' is the first member without initialization it get the default
value '0'. Because of this the following flush condition never succeeds.

if (m_flags & FLUSH_F)
  fflush(m_file);

At present the file gets flushed only during my_fclose(result_file) operation.
When continuous streaming is enabled through --stop-never option it never gets
flushed and hence events are not replicated.

Fix:
===
Initialize the enum value to non zero value.

Problem was that tests select INFORMATION_SCHEMA.PROCESSLIST processes
from user system user and empty state. Thus, there is not clear
state for slave threads.

Changes:
- Added new status variables that store current amount of applier threads
(wsrep_applier_thread_count) and rollbacker threads
(wsrep_rollbacker_thread_count). This will make clear how many slave threads
of certain type there is.
- Added THD state "wsrep applier idle" when applier slave thread is
waiting for work. This makes finding slave/applier threads easier.
- Added force-restart option for mtr to always restart servers between tests
to avoid race on start of the test
- Added wait_condition_with_debug to wait until the passed statement returns
true, or the operation times out. If operation times out, the additional error
statement will be executed

Changes to be committed:
	new file:   mysql-test/include/force_restart.inc
	new file:   mysql-test/include/wait_condition_with_debug.inc
	modified:   mysql-test/mysql-test-run.pl
	modified:   mysql-test/suite/galera/disabled.def
	modified:   mysql-test/suite/galera/r/MW-336.result
	modified:   mysql-test/suite/galera/r/galera_kill_applier.result
	modified:   mysql-test/suite/galera/r/galera_var_slave_threads.result
	new file:   mysql-test/suite/galera/t/MW-336.cnf
	modified:   mysql-test/suite/galera/t/MW-336.test
	modified:   mysql-test/suite/galera/t/galera_kill_applier.test
	modified:   mysql-test/suite/galera/t/galera_parallel_autoinc_largetrx.test
	modified:   mysql-test/suite/galera/t/galera_parallel_autoinc_manytrx.test
	modified:   mysql-test/suite/galera/t/galera_var_slave_threads.test
	modified:   mysql-test/suite/wsrep/disabled.def
	modified:   mysql-test/suite/wsrep/r/variables.result
	modified:   mysql-test/suite/wsrep/t/variables.test
	modified:   sql/mysqld.cc
	modified:   sql/wsrep_mysqld.cc
	modified:   sql/wsrep_mysqld.h
	modified:   sql/wsrep_thd.cc
	modified:   sql/wsrep_var.cc

was getting rows=2 instead of 1 on kvm-rpm-centos74-amd64

Use RocksDB debug sync points to introduce a sync delay. This
commits to get grouped even when the datadir is on ramdisk.

For some unclear reason the effect is visible on write_prepared
but not write_committed, so run the test only with write_prepared.

Problem:
=======
  Checksum fields can have value as zero. In that case, InnoDB falsely
consider that page should be all zeroes. It leads to wrong detection of page
corruption.

Solution:
========
	Remove the condition that checks if checksum fields are zero then
page should be all zeroes.