We introduce simple plugin dependency. A plugin init function may
return HA_ERR_RETRY_INIT. If this happens during server startup when
the server is trying to initialise all plugins, the failed plugins
will be retried, until no more plugins succeed in initialisation or
want to be retried.

This will fix spider init bugs which is caused in part by its
dependency on Aria for initialisation.

The reason we need a new return code, instead of treating every
failure as a request for retry, is that it may be impossible to clean
up after a failed plugin initialisation. Take InnoDB for example, it
has a global variable `buf_page_cleaner_is_active`, which may not
satisfy an assertion during a second initialisation try, probably
because InnoDB does not expect the initialisation to be called
twice. A test that may fail because of this is
`encryption.corrupted_during_recovery`, see for example[1], which is
tested at 73835f64b7fc245d38812380685aca03bef72bb5, a previous commit
where we retry every failed plugin.

[1] https://buildbot.mariadb.org/#/builders/369/builds/10107/steps/7/logs/stdio

Will re-enable once MDEV-31101 is no longer blocked by MDEV-22979,
as the patch for the latter might fix the former.

The server needs to have a unique name

spider_db_mbase_util::open_item_func() is a monster function.
It is difficult to maintain while it is expected that we need to
modify it when a new SQL function or a new func_type is added.

We split the function into two distinct functions: one handles the
case of str != NULL and the other handles the case of str == NULL.

This refactoring was done in a conservative way because we do not
have comprehensive tests on the function.

It also fixes MDEV-29447 and MDEV-31338 where field items that are
arguments of a func item may be used before created / initialised.

Note this commit is adapted from a patch by Nayuta for MDEV-26285.

Extract the indexed string memcopy pattern in spd_trx.cc to a static
inline function.

Also updated the ubsan check in mdev_26541.test (h/t roel).

recv_sys_t::parse(): For undo tablespace truncation mini-transactions,
remember the start_lsn instead of the end LSN. This is what we expect
after commit 461402a5 (MDEV-30479).

mysql.proc. The table is probably corrupted"

Analysis: When mysql_upgrade runs statements for upgrade, characterset is
converted to utf8mb4 because server starts with old_mode that interprets
utf8 to utf8mb4, but mysql.proc table has "utf8mb3" as hardcoded, so
it crashes with corrupted table.

Fix: Changed Table_check_intact::check() definition to allow both
utf8mb3 and utf8mb4 by checking prefix and changing the upgrade scripts
to explicitly use utf8mb3

MDEV-29253 Detect incompatible MySQL partition scheme and either convert
them or report to user and in error log.

This task is about converting in place MySQL 5.6 and 5.7 partition tables
to MariaDB as part of mariadb-upgrade.

- Update TABLE_SHARE::init_from_binary_frm_image() to be able to read
  MySQL frm files with partitions.
- Create .par file, if it do not exists, on open of partitioned table.

Executing mariadb-upgrade will create all the missing .par files.
The MySQL .frm file will be changed to MariaDB format after next
ALTER TABLE.

Other changes:
- If we are using stored mysql_version to distingush between MySQL and
  MariaDB  .frm file information, do not upgrade mysql_version in the
  .frm file as part of CHECK TABLE .. FOR UPGRADE as this would cause
  problems next time we parse the .frm file.

- Moved view checks after privilege tables are fixed. This is to avoid
  warnings about wrongly defined mysql.proc when checking views.
- Don't use stat tables before they have been fixed.
- Don't run mysql_fix_view() if 'FOR MYSQL' is used if the view is
  already a MariaDB view.
- Added 'FOR UPGRADE' as an option for 'REPAIR VIEW' to be able to
  detect if the REPAIR command comes from mariadb_upgrade. In this
  case we get a warning, instead of an error, if a definer of a view
  does not exists.

In this case, one would end up calling my_error(ER_BAD_DB_ERROR, ...)
with a null ptr for DB, which caused a NULL ptr dereference.

The original code generated a warning in gcc 13.1

When opening and locking tables, if triggers will be invoked in a
separate database, thd->set_db() is invoked, thus freeeing the memory
and headers which thd->db had previously pointed to. In row based
replication, the event execution logic initializes thd->db to point
to the database which the event targets, which is owned by the
corresponding table share (introduced in d9898c9a for MDEV-7409).
The problem then, is that during the table opening and locking
process for a row event, memory which belongs to the table share
would be freed, which is not valid.

This patch replaces the thd->reset_db() calls to thd->set_db(),
which copies-by-value, rather than by reference. Then when the
memory is freed, our copy of memory is freed, rather than memory
which belongs to a table share.

Notes:
  1. The call to change thd->db now happens on a higher-level, in
Rows_log_event::do_apply_event() rather than ::do_exec_row(), in the
call stack. This is because do_exec_row() is called within a loop,
and each invocation would redundantly set and unset the db to the
same value.
  2. thd->set_db() is only used if triggers are to be invoked, as
there is no vulnerability in the non-trigger case, and copying
memory would be an unnecessary inefficiency.

Reviewed By:
============
Andrei Elkin <andrei.elkin@mariadb.com>

- InnoDB shouldn't acquire the tablespace when it is being stopped
or closed

Fix a typo in make_join_statistics(): when updating statistics for
derived table, set s->table->... not "table->..."

(Same as
TODO-3938: best_access_path shows negative costs for mrr=on)

best_access_path() assumes that quick select cost includes
(quick->rows/TIME_FOR_COMPARE) as a cost of checking the attached
part of the WHERE condition.

It calls adjust_quick_cost() to subtract addition from quick's cost.

The problem was that DS-MRR cost formula didn't include this cost.
For very large tables, adjust_quick_cost() would produce a negative
cost which would cause assert in debug build or bad query plan choice
in release builds.
Approved-by: Monty <monty@mariadb.org>

The effect was that that ROOT_FLAG_THREAD_SPECIFIC was cleared and
the memory allocated by memroot would be contributed the the system,
not to the thread.

This exposed a bug in how "show explain for ..." allocated data.
- The thread that did provide the explain allocated data in the
  "show explain" threads mem_root, which is marked as THREAD_SPECIFIC.
- Fixed by allocating the explain data in a temporary explain_mem_root
  which is not THREAD_SPECIFIC.

Other things:
- Added extra checks when using update_malloc_size()
- Do not call update_malloc_size() for memory not registered with
  update_malloc_size(). This avoid some wrong 'memory not freed' reports.
- Added a checking of 'thd->killed' to ensure that
  main.truncate_notembedded.test still works.

Reported by: Yury Chaikou

After further I/O on a tablespace has been stopped
(for example due to DROP TABLE or an operation that
rebuilds a table), page cleaner thread tries to
flush the pending writes for the tablespace and
releases the tablespace reference even though it was not
acquired.

fil_space_t::flush(): Don't release the tablespace when it is
being stopped and closed

Thanks to Marko Mäkelä for suggesting this patch.

Commit fixes Debian SySV-init script fail:
  /etc/init.d/mariadb: line 90: [: : integer expression expected
which happens if datadir is not changed in configuration which
makes it invisible when printing MariaDB config defaults.

Commit makes sure that there is some value if nothing else if in hand
use default /usr/lib/mysql or fail with correct error message if
directory is not present

- InnoDB throws ASAN error while adding the index on virtual column
of system versioned table. InnoDB wrongly assumes that virtual
column collation type changes, creates new column with different
character set. This leads to failure while detaching the column
from indexes.

embedded doesn't have optimizer trace,
view-protocol doesn't work with long column names.

The test gcol.gcol_purge would reliably hang on 10.6 on a
Microsoft Windows builder without this adjustment.
A similar adjustment was applied in
commit 3e40f9a7
to the tests innodb.dml_purge and innodb.instant_alter_purge.

innodb_undo_log_truncate_update(): A callback function. If
SET GLOBAL innodb_undo_log_truncate=ON, invoke
srv_wake_purge_thread_if_not_active().

srv_wake_purge_thread_if_not_active(): If innodb_undo_log_truncate=ON,
always wake up the purge subsystem.

srv_do_purge(): If the history is empty, invoke
trx_purge_truncate_history() in order to free undo log pages.

trx_purge_truncate_history(): If head.trx_no==0, consider the
cached undo logs to be free.

trx_purge(): Remove the parameter "bool truncate" and let the
caller invoke trx_purge_truncate_history() directly.

Reviewed by: Vladislav Lesin

purge_sys_t::sees(): Wrapper for view.sees().

trx_purge_truncate_history(): Invoke purge_sys.sees() instead of
comparing to head.trx_no, to determine if undo pages can be safely freed.

The test innodb.cursor-restore-locking was adjusted by Vladislav Lesin,
as was the the debug instrumentation in row_purge_del_mark().

Reviewed by: Vladislav Lesin