The option innodb_log_compressed_pages was contributed by
Facebook to MySQL 5.6. It was disabled in the 5.6.10 GA release
due to problems that were fixed in 5.6.11, which is when the
option was enabled.

The option was set to innodb_log_compressed_pages=ON by default
(disabling the feature), because safety was considered more
important than speed. The option innodb_log_compressed_pages=OFF
can *CORRUPT* ROW_FORMAT=COMPRESSED tables on crash recovery
if the zlib deflate function is behaving differently (producing
a different amount of compressed data) from how it behaved
when the redo log records were written (prior to the crash recovery).

In MDEV-6935, the default value was changed to
innodb_log_compressed_pages=OFF. This is inherently unsafe, because
there are very many different environments where MariaDB can be
running, using different zlib versions. While zlib can decompress
data just fine, there are no guarantees that different versions will
always compress the same data to the exactly same size. To avoid
problems related to zlib upgrades or version mismatch, we must
use a safe default setting.

This will reduce the write performance for users of
ROW_FORMAT=COMPRESSED tables. If you configure
innodb_log_compressed_pages=ON, please make sure that you will
always cleanly shut down InnoDB before upgrading the server
or zlib.

The test did not handle correctly possible difference in system
timezone. The fix is to remove non-functional setting of local
time_zone and instead allow timestamp replacement to work with
any date/time

Patch submitted by Eugene Kosov <claprix@yandex.ru>,
comments added by commiter.
Signed-off-by: Vicențiu Ciorbaru <vicentiu@mariadb.org>

When using innodb_page_size=16k, InnoDB tables
that were created in MariaDB 10.1.0 to 10.1.20 with
PAGE_COMPRESSED=1 and
PAGE_COMPRESSION_LEVEL=2 or PAGE_COMPRESSION_LEVEL=3
would fail to load.

fsp_flags_is_valid(): When using innodb_page_size=16k, use a
more strict check for .ibd files, with the assumption that
nobody would try to use different-page-size files.

If open of the relay log failed, we got an assert in MYSQL_BIN_LOG::close
This only affected DEBUG systems

CREATE/DROP TEMPORARY TABLE are not safe to optimistically replicate in
parallel with other transactions, so they need to be marked as "ddl" in the
binlog.

This was already done for stand-alone CREATE/DROP TEMPORARY. But temporary
tables can also be created and dropped inside a BEGIN...END transaction, and
such transactions were not marked as ddl. Nor was the DROP TEMPORARY TABLE
statement emitted implicitly when a client connection is closed.

So this patch adds such ddl mark for the missing cases.

The difference to Kristian's original patch is mainly a fix in
mysql_trans_commit_alter_copy_data() to remember the unsafe_rollback_flags
over the temporary commit.

MDEV-11646 main.myisam, maria.maria, main.mix2_myisam, main.myisampack, main.mrr_icp_extra fail in buildbot with valgrind (Syscall param pwrite64(buf) points to uninitialised byte(s))

If the table has a varchar column and a forced fixed for format
(as in varchar.inc), Field_varstring::store() will only store the
actual number of bytes, not padded, in the record[0].

That is, on inserts a part of record[0] can be uninitialized.

Fix: initialize record[0] when a TABLE is created, it doesn't matter
what kind of garbage can be in this unused/invisible part of the
record, as long as it's not some random memory contents
(that can contain sensitive data).

Fix the binding of databases_file. It was incorrectly mapped
to OPT_XTRA_TABLES_FILE.

Remove some unused options and variables.

tmp variable now points to str->ptr() buffer, not tmp_value buffer.
Comparing pointers otherwise can lead to false assertion errors as we
don't know where buffers are allocated in respect to each other.

cover ANSI_QUOTES and NO_BACKSLASH_ESCAPES in mysqltest

don't do backslash escapes inside backticks

Item_func_sysconst behaves as a non-constant function during prepared
statements and view creation and constant otherwise. Current condition
implied the opposite.

MDEV-10880: Assertions `keypart_map' or `prebuilt->search_tuple->n_fields > 0' fail on DISTINCT and GROUP BY constant

add_group_and_distinct_keys() should take into account JOIN::simple_group.

prepare of "fake_select" for union made in JOIN::prepare only if
we do not execute it then before reset, i.e it was for PS prepare
and now required for CREATE VIEW to make global ORDER BY which
belongs to "fake_select" prepared.

https://github.com/percona/percona-xtrabackup/pull/368/commits/72c55f4fc2ba9ede7b960eceb01261ccc339c041

fix a merge mistake

MyISAM only allows online alter if autoincrement didn't change.
MyISAM detects that by comparing new autoinc value from create_info,
with the old one, stored in MYI. But in partitioned tables,
create_info->auto_increment_value is for the whole table, max of
autoinc values of individual MYI partitions. So *some* MYI partitions
will inevitably think that alter table changes auto_increment value
and will deny online alter.

Fix: only compare autoinc values, if the user has used AUTO_INCREMENT
in the ALTER TABLE statement.

MDEV-13012 Assertion `share->error' failed in discover_handlerton upon executing statement with max_session_mem_used = 8192

and
MDEV-13011 Server crashes in THD::handle_condition or Assertion `! is_set() || m_can_overwrite_status' fails upon attempt to connect with max_session_mem_used = 8192

errors when a connection is killed in the
* TABLE_SHARE::init_from_sql_statement_string()
* THD::init()

also, safety-wise, don't check max_mem_used on free() and when some error
was already issued.

it was disabled in mtr tests in 4280b25e

Comment from Codership:-
To fix the problem, we changed the certification logic in galera to treat insert
on child table row as exclusive to prevent any operation on referenced
parent table row. At the same time, update and delete on
 child table row were demoted to "shared", which makes it possible to
update/delete referenced parent table row, but only in a later transaction.
 This change allows somewhat more concurrency for foreign key constrained
 transactions, but is still safe for correct certification end result.

using "show variables", rather than take the value from my.cnf.

"show variables" is more accurate than my.cnf,it also works for parameters
set on the mysqld command line, which is especially important for MTR.

MDEV-12975 InnoDB redo log minimum size check uses detected file size instead of requested innodb_log_file_size

log_calc_max_ages(): Use the requested size in the check, instead of
the detected redo log size. The redo log will be resized at startup
if it differs from what has been requested.