A race condition may occur between the execution of transaction commit,
and an execution of a KILL statement that would attempt to abort that
transaction.

MDEV-17092 worked around this race condition by modifying InnoDB code.
After that issue was closed, Sergey Vojtovich pointed out that this
race condition would better be fixed above the storage engine layer:

If you look carefully into the above, you can conclude that
thd->free_connection() can be called concurrently with
KILL/thd->awake(). Which is the bug. And it is partially fixed in
THD::~THD(), that is destructor waits for KILL completion:

Fix: Add necessary mutex operations to THD::free_connection()
and move WSREP specific code also there. This ensures that no
one is using THD while we do free_connection(). These mutexes
will also ensures that there can't be concurrent KILL/THD::awake().

innobase_kill_query
  We can now remove usage of trx_sys_mutex introduced on MDEV-17092.

trx_t::free()
  Poison trx->state and trx->mysql_thd

This patch is validated with an RQG run similar to the one that
reproduced MDEV-17092.

Ensure consistent use of logging macros in wsrep-related code
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

btr_discard_only_page_on_level(): Attempt to read the MDEV-15562 metadata
record from the leaf page, not the root page. In the root, the leftmost
(in this case, the only) node pointer would look like a metadata record.

This corruption bug was introduced in
commit 0e5a4ac2 (MDEV-15562).
The scenario is rare: a column was dropped instantly or the order of
columns was changed instantly, and then the table became empty in such
a way that in the last step, the root page had one child page.
Normally, a non-leaf B-tree page would always contain at least 2 children.

Let us use Intel intrinsic functions in WolfSSL whenever possible.
This allows such code to be compiled WITH_MSAN.

(correction for commit 6fed6de9)

Under ps-protocol, commandsl like COM_STMT_FETCH, COM_STMT_CLOSE and
COM_STMT_SEND_LONG_DATA are not supposed to return errors. Therefore,
if a transaction is BF aborted and the client is processing one of
those commands, then we should not return a deadlock error
immediately. Instead wait for the a subsequent client interaction
which permits errors to be returned. To handle this,
wsrep_before_command() now accepts parameter keep_command_error. If
set true, keep_command_error will cause wsrep-lib side to skip result
handling, and to keep the current error for the next interaction with
the client.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

This corresponds to 10.5 commit 39378e13.

With a patched version of the test innodb.ibuf_not_empty (so that
it would trigger crash recovery after using the change buffer),
and patched code that would modify the os_thread_sleep() in
recv_apply_hashed_log_recs() to be 1ms as well as add a sleep of
the same duration to the end of recv_recover_page() when
recv_sys->n_addrs=0, we can demonstrate a race condition.

After disabling some debug checks in buf_all_freed_instance(),
buf_pool_invalidate_instance() and buf_validate(), we managed to
trigger an assertion failure in fseg_free_step(), on the XDES_FREE_BIT.
In other words, an trx_undo_seg_free() call during
trx_rollback_resurrected() was attempting a double-free of a page.
This was repeated about once in 400 to 500 test runs. With the fix
applied, the test passed 2,000 runs.

recv_apply_hashed_log_recs(): Do not only wait for recv_sys->n_addrs
to reach 0, but also wait for buf_get_n_pending_read_ios() to reach 0,
to guarantee that buf_page_io_complete() will not be executing
ibuf_merge_or_delete_for_page().

Issues MDEV-23851 and MDEV-24229 are probably duplicates and are caused by the new self-asserting function lock0lock.cc:wsrep_assert_no_bf_bf_wait().
The criteria for asserting is too strict and does not take in consideration scenarios of "false positive" lock conflicts, which are resolved by replaying the local transaction.
As a fix, this PR is relaxing the assert criteria by two conditions, which skip assert if high priority transactions are locking in correct order or if conflicting high priority lock holder is aborting and has just not yet released the lock.

Alternative fix would be to remove wsrep_assert_no_bf_bf_wait() altogether, or remove the assert in this function and let it only print warnings in error log.
But in my high conflict rate multi-master test scenario, this relaxed asserting appears to be safe.

This PR also removes two wsrep_report_bf_lock_wait() calls in innodb lock manager, which cause mutex access assert in debug builds.

Foreign key appending missed handling of data types of float and double in INSERT execution. This is not directly related to the actual issue here but is fixed in this PR nevertheless. Missing these foreign keys values in certification could cause problems in some multi-master load scenarios.

Finally, some problem reports suggest that some of the issues reported in MDEV-23851 might relate to false positive lock conflicts over unique secondary index gaps. There is separate work for relaxing UK index gap locking of replication appliers, and separate PR will be submitted for it, with a related mtr test as well.

dbug_print_rec() functions used to print data inside GDB.

Remove the unused dbug_print_rec() functions because they break
the clang build due to -Wreturn-stack-address

Fix a trivial error in the fix for MDEV-21958: check the key in the right
table.

Galera replication does not support XA transactions yet. Reject any
attempt to `XA START` a transaction, if Galera is enabled.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

Add history row outside of compare_record() check. For TRX_ID
versioning we have to fail can_compare_record to force InnoDB update
which adds history row; and there in ha_innobase::update_row() is
additional "row changed" check where we force history row anyway.

MDEV-23644 Assertion on evaluating foreign referential action for self-reference in system versioned table

First part of the fix (row0mysql.cc) addresses external columns when adding history
row on referential action. The full data must be retrieved before the
row is inserted.

Second part of the fix (the rest) avoids duplicate primary key error between
the history row generated on referential action and the history row
generated by SQL command. Both command and referential action can
happen on same table since foreign key can be self-reference (parent
and child tables are same). Moreover, the self-reference can refer
multiple rows when the key is non-unique. In such case history is
generated by referential action occured on first row but processed all
rows by a matched key. The second round is when the next row is
processed by a command but history already exists. In such case we
check TRX_ID of existing history row and if it is the same we assume
the above situation and skip adding one more history row or failing
the command.

First part (row0mysql.cc) fixes ins_node_set_new_row() usage workflow
as it is designed to operate on empty row (see row_get_prebuilt_insert_row()
for example).

Second part (row0ins.cc) fixes duplicate key error in FTS_DOC_ID_INDEX
since history rows must not generate entries in that index. We detect
FTS_DOC_ID_INDEX by a number of attributes and skip it if the row is
historical.

Misc fixes:

row_build_index_entry_low() does not accept non-NULL tuple
for FTS index (subject assertion fails), assertion (index->type !=
DICT_FTS) adds code understanding.

Now as historical_row is copied in row_update_vers_insert() there is
no need to copy the row twice: ROW_COPY_POINTERS is used to build
historical_row initially.

dbug_print_rec() debug functions.

MDEV-22178 Assertion `info->alias.str' failed in partition_info::check_partition_info instead of ER_VERS_WRONG_PARTS

Assign create_info->alias for ALTER TABLE since it is NULL and later
accessed for printing error message.

Closing remaining threads in `wsrep_close_client_connections` should also
check `thd_is_connection_alive` for thd before closing connection. Assert is
happening when thread already doing shutdown, but still not removed from threads
list.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

MDEV-22630 mysql_upgrade (MariaDB 5.2.X --> MariaDB 10.3.X) does not fix auth_string to change it to authentication_string

cherry-pick from 10.4:

  commit b976b9bf
  Author: Sergei Golubchik <serg@mariadb.com>
  Date:   Tue Apr 21 18:40:15 2020 +0200

    MDEV-21244 mysql_upgrade creating empty global_priv table

    support upgrades from 5.2 privilege tables

in particular, it caused escape_item->is_expensive() property
to be lost instead of being properly propagated up.

Part II.

It's still possible to bypass Item_func_like::escape
initialization in Item_func_like::fix_fields().

This requires ESCAPE argument being a cacheable subquery
that uses tables and is inside a derived table which
is used in multi-update.

Instead of implementing a complex or expensive fix for
this particular ridiculously artificial case, let's simply disallow it.

in queries like

  create view v1 as select 2 like 1 escape (3 in (select 0 union select 1));
  select 2 union select * from v1;

Item_func_like::escape was left uninitialized, because
Item_in_optimizer is const_during_execution()
but not actually const_item() during execution.

It's not, because const subquery evaluation was disabled for derived.
Practically it only needs to be disabled for multi-update
that runs fix_fields() before all tables are locked.

this happens if Item_func_like is copied (get_copy()).
after one copy gets fixed, the other tries to fix escape item again.

At end_connection make sure we have wsrep before trying to free
connection assigned to it.

MDEV-22008 rpl.rpl_semi_sync fails in bb, MDEV-24418 reenable binlog_truncate_innodb and binlog_spurious_ddl_errors, rpl_parallel_retry fails in bb

row_upd_clust_step() calls row_upd_del_mark_clust_rec() which would
allocate some memory in row_ins_foreign_fill_virtual(). Then,
row_upd_store_row() would access the allocated memory, but only after
potentially freeing that memory by invoking mem_heap_empty(),
leading to ASAN heap-use-after-free diagnostics.

row_ins_foreign_fill_virtual(): Use a more appropriate memory heap with a
longer lifetime.

Due to this bug the server reported bogus messages about lack of SELECT
privileges for base tables used in the specifications of CTE tables.
It happened only if such a CTE were referred to at least twice.
For any non-recursive reference to CTE that is not primary the
specification of the CTE is cloned. The function check_table_access() is
called for such reference. The function checks privileges of the tables
referenced in the specification. As no name resolution was performed for
CTE references whose definitions occurred outside the specification before
the call of check_table_access() that was supposed to check the access
rights of the underlying tables these references were considered
as references to base tables rather than references to CTEs. Yet for CTEs
as well as for derived tables no privileges are needed and thus cannot
be granted.
The patch ensures proper name resolution of all references to CTEs before
any acl checks.

Approved by Oleksandr Byelkin <sanja@mariadb.com>