It turns out that we had some unnecessary waits for no outstanding
write requests to exist. They were basically working around a
bug that was fixed in MDEV-25953.

On write completion callback, blocks will be marked clean.
So, it is sufficient to consult buf_pool.flush_list to determine
which writes have not been completed yet.

On FLUSH TABLES...FOR EXPORT we must still wait for all pending
asynchronous writes to complete, because buf_flush_file_space()
would merely guarantee that writes will have been initiated.

Cherry-picking only test case.

trx_undo_mem_create_at_db_start(): Relax too strict upgrade checks
that were introduced in
commit e46f76c9 (MDEV-15912).
On commit, pages will typically be set to TRX_UNDO_CACHED state.
Having the type TRX_UNDO_INSERT in such pages is common and
unproblematic; the type would be reset in trx_undo_reuse_cached().

trx_rseg_array_init(): On failure, clean up the rollback segments
that were initialized so far, to avoid an assertion failure later
during shutdown.

init_crypt_key(): On failure, set info->key_version to
ENCRYPTION_KEY_VERSION_INVALID.

log_crypt_101_read_block(): Refuse to attempt decryption if
info->key_version is ENCRYPTION_KEY_VERSION_INVALID.

This bug affected queries with views / derived_tables / CTEs whose
specifications were of the form
  (SELECT ... LIMIT <n>) ORDER BY ...
Units representing such specifications contains one SELECT_LEX structure
for (SELECT ... LIMIT <n>) and additionally SELECT_LEX structure for
fake_select_lex. This fact should have been taken into account in the
function mysql_derived_fill().

This patch has to be applied to 10.2 and 10.3 only.

This bug affected queries with views / derived_tables / CTEs whose
specifications were of the form
  (SELECT ... LIMIT <n>) ORDER BY ...
Units representing such specifications contains one SELECT_LEX structure
for (SELECT ... LIMIT <n>) and additionally SELECT_LEX structure for
fake_select_lex. This fact should have been taken into account in the
function mysql_derived_fill().

This patch has to be applied to 10.2 and 10.3 only.

trx_undo_report_row_operation(): Fix a race condition that was introduced
in commit f74023b9 (MDEV-15090).
We must not access undo_block after the page latch has been released
in mtr_t::commit(), because the block could be evicted or replaced.

In the merge commit d3e4fae7
a message about innodb_force_recovery was accidentally duplicated.

- Adding socket check for MariaDB/Mysql driver

Reviewed by: serg@mariadb.com

mytop fall-back to DBD::mysql if DBD::MariaDB is not available

Apply #1546

Let us simply refuse an upgrade from earlier versions if the
upgrade procedure was not followed. This simplifies the purge,
commit, and rollback of transactions.

Before upgrading to MariaDB 10.3 or later, a clean shutdown
of the server (with innodb_fast_shutdown=1 or 0) is necessary,
to ensure that any incomplete transactions are rolled back.
The undo log format was changed in MDEV-12288. There is only
one persistent undo log for each transaction.

Builds on travis-ci.org ceased on 2021-06-15.

see also 068246c0 and 690ae1de

see also 068246c0

see also a5f6eca5

spider tests use

--let $var= many;sql;statements
--eval $var

and this doesn't work in ps

and *never* disable tests in suite.pm based on $::opt_big_test,
this will make the test skipped both as too big (for ./mtr)
and as too small (for ./mtr --big --big).

MDEV-25867 main.trigger-trans failed in bb, Assertion `ticket->m_duration == MDL_EXPLICIT' failed in MDL_context::release_lock

release MDL on the trigger as early as possible, after everything that
cannot be done concurrently was done (under MDL), but before relocking
tables.

Do not execute user callback just after pwrite. Instead, submit user
function as task into thread pool. This way, the IO thread would not hog
aiocb, which is a limited (in Innodb) resource

- Make innodb_fts.misc_debug test case more stable.

Add fixed for tests mysqld--help,aix.rdiff and sysvars_server_notembedded,aix.rdiff

AIX couldn't compile in embedded mode so leaving sysvars_server_embedded
for later (if required).

In commit 1c35a3f6 a useless
computation that used the variable was removed.

Additional improvements aimed at improving operational
reliability of the SST scripts:

1) Script need to give rsync and stunnel a short time to
   terminate after "kill -9" before the first PID check
   using ps utility;
2) The temporary file used to create the binlog index could
   sometimes remain in the data directory if tar failed and
   then may be reused without being cleaned up (the next
   time when SST was run) - now it's fixed;
3) The temporary file used to build the binlog index is now
   created using mktemp and, if this variable is present in
   the configuration file, in tmpdir;
4) Checking the secret tag in SST via rsync is made faster
   and does not require creating a temporary file, which
   could remain in the data directory in case of failure;
5) Added "-F" option to grep to check the tag when using
   mariabackup/xtrabackup-v2 - to avoid possible collisions
   in case of special characters in the tag value (unlikely
   scenario, but the new check is more reliable).

This commit fixes a bug was originally discovered during the
galera_nbo_sst_slave mtr test for 10.6 branch. However it is
relevant for all versions and can lead to intermittent SST
crashes via rsync on very fast server restarts - when a new
SST process (for example, after starting a new server instance)
overlaps the old SST process started by the previous, already
terminated server. This overlap can result in the new rsync
being killed instead of the old rsync, or the pid file from
the new rsync being killed, which then lead to problems.

a new warning -Wunused-but-set-variable was introduced recently to clang

- During online alter conversion from compact to redundant,
virtual column field length already set during
innobase_get_computed_value(). Skip the char(n) check for
virtual column in row_merge_buf_add()

MDEV-25872 InnoDB: Assertion failure in row_merge_read_clustered_index upon ALTER on table with indexed virtual columns

- InnoDB fails to check DB_COMPUTE_VALUE_FAILED error in
row_merge_read_clustered_index() and wrongly asserts that
the buffer shouldn't be ran out of memory. Alter table
should give warning when the column value is being
truncated.