The fix of MDEV-17556 (commit e25623e7
and commit 61a362c9) has been
omitted due to conflicts and will have to be applied separately later.

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.

The assertion failed in handler::ha_reset upon SELECT under
READ UNCOMMITTED from table with index on virtual column.

This was the debug-only failure, though the problem is mush wider:
* MY_BITMAP is a structure containing my_bitmap_map, the latter is a raw
 bitmap.
* read_set, write_set and vcol_set of TABLE are the pointers to MY_BITMAP
* The rest of MY_BITMAPs are stored in TABLE and TABLE_SHARE
* The pointers to the stored MY_BITMAPs, like orig_read_set etc, and
 sometimes all_set and tmp_set, are assigned to the pointers.
* Sometimes tmp_use_all_columns is used to substitute the raw bitmap
 directly with all_set.bitmap
* Sometimes even bitmaps are directly modified, like in
TABLE::update_virtual_field(): bitmap_clear_all(&tmp_set) is called.

The last three bullets in the list, when used together (which is mostly
always) make the program flow cumbersome and impossible to follow,
notwithstanding the errors they cause, like this MDEV-17556, where tmp_set
pointer was assigned to read_set, write_set and vcol_set, then its bitmap
was substituted with all_set.bitmap by dbug_tmp_use_all_columns() call,
and then bitmap_clear_all(&tmp_set) was applied to all this.

To untangle this knot, the rule should be applied:
* Never substitute bitmaps! This patch is about this.
 orig_*, all_set bitmaps are never substituted already.

This patch changes the following function prototypes:
* tmp_use_all_columns, dbug_tmp_use_all_columns
 to accept MY_BITMAP** and to return MY_BITMAP * instead of my_bitmap_map*
* tmp_restore_column_map, dbug_tmp_restore_column_maps to accept
 MY_BITMAP* instead of my_bitmap_map*

These functions now will substitute read_set/write_set/vcol_set directly,
and won't touch underlying bitmaps.

MDEV-16272 rpl.rpl_semisync_ali_issues failed in buildbot, SHOW variable was done instead of waiting for the value of that variable

Use the same variable in both scopes (from where we have "goto error" and target of the goto)

Problem: Assertion `transactional_table || !changed ||
thd->transaction.stmt.modified_non_trans_table' failed due REPLACE into a
versioned table.

It is not specific to system versioning/pertitioning/heap, but this
combination makes it much easier to reproduce.

The thing is to make first ha_update_row call succeed to make
info->deleted != 0. And then make REPLACE fail by any reason.

In this scenario we overflow versioned partition, so next ha_update_row
succeeds, but corresponding ha_write_row fails to insert history record.

Fix: modified_non_trans_table is set in one missed place

fixing windows build.

mysql_col_offset was not updated after the new column has been added by an
INSTANT ALTER TABLE -- table data dictionary had been remaining the same.

When the virtual column is added or removed, table was usually evicted and
then reopened, which triggered vcol info rebuild on the next open.

However this also should be done when the usual column is added or removed:
mariadb always stores virtual field at the end of maria record,
so the shift should always happen.

Fix:
expand the eviction condition to the case when usual fields are
added/removed

Note:
this should happen only in the case of !new_clustered:
* When new_clustered is true, a new data dictionary is created, and vcol
metadata is rebuilt in `alter_rebuild_apply_log()`
* We can't do it in `new_clustered` case, because the old table is not yet
subctituted correctly

Problem:
=======
Upon deleting or updating a row in a parent table (with primary key), if
the child table has virtual column and an associated key with ON UPDATE
CASCADE/ON DELETE CASCADE, it will result in slave crash.

Analysis:
========
Tables which are related through foreign key require prelocking similar to
triggers. i.e If a table has triggers/foreign keys we should add all tables
and routines used by them to the prelocking set.  This prelocking happens
during 'open_and_lock_tables' call.  Each table being opened is checked for
foreign key references. If foreign key reference exists then the child
table is opened and it is linked to the table_list. Upon any modification
to  parent table its corresponding child tables are retried from table_list
and they are updated accordingly. This prelocking work fine on master.

On slave  prelocking works for following cases.
 - Statement/mixed based replication
 - In row based replication when trigger execution is enabled through
   'slave_run_triggers_for_rbr=YES/LOGGING/ENFORCE'

Otherwise it results in an assert/crash, as the parent table will not find
the corresponding child table and it will be NULL. Dereferencing NULL
pointer leads to slave server exit.

Fix:
===
Introduce a new 'slave_fk_event_map' flag similar to 'trg_event_map'. This
flag will ensure that when foreign key is enabled in row based replication
all the parent and child tables are prelocked, so that parent is able to
locate the child table.

Note: This issue is specific to slave, hence only slave needs to be
      upgraded.

Analysis: select into outfile creates files everytime with 666 permission,
regardsless if umask environment variables and umask settings on OS level.
It seems hardcoded.
Fix: change 0666 to 0644 which will let anybody consume the file but not
change it.

(correction for commit 6fed6de9)

MDEV-19442 server_audit plugin doesn't consider proxy users in server_audit_excl_users/server_audit_incl_users.

Check the proxy user just as the connection user against the
incl_users_list and excl_users_list.

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.

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.