It is not safe to invoke trx_purge_free_segment() or execute
innodb_undo_log_truncate=ON before all undo log records in
the rollback segment has been processed.

A prominent failure that would occur due to premature freeing of
undo log pages is that trx_undo_get_undo_rec() would crash when
trying to copy an undo log record to fetch the previous version
of a record.

If trx_undo_get_undo_rec() was not invoked in the unlucky time frame,
then the symptom would be that some committed transaction history is
never removed. This would be detected by CHECK TABLE...EXTENDED that
was impleented in commit ab019010.
Such a garbage collection leak should be possible even when using
innodb_undo_log_truncate=OFF, just involving trx_purge_free_segment().

trx_rseg_t::needs_purge: Change the type from Boolean to a transaction
identifier, noting the most recent non-purged transaction, or 0 if
everything has been purged. On transaction start, we initialize this
to 1 more than the transaction start ID. On recovery, the field may be
adjusted to the transaction end ID (TRX_UNDO_TRX_NO) if it is larger.

The field TRX_UNDO_NEEDS_PURGE becomes write-only; only some debug
assertions that would validate the value. The field reflects the old
inaccurate Boolean field trx_rseg_t::needs_purge.

trx_undo_mem_create_at_db_start(), trx_undo_lists_init(),
trx_rseg_mem_restore(): Remove the parameter max_trx_id.
Instead, store the maximum in trx_rseg_t::needs_purge,
where trx_rseg_array_init() will find it.

trx_purge_free_segment(): Contiguously hold a lock on
trx_rseg_t to prevent any concurrent allocation of undo log.

trx_purge_truncate_rseg_history(): Only invoke trx_purge_free_segment()
if the rollback segment is empty and there are no pending transactions
associated with it.

trx_purge_truncate_history(): Only proceed with innodb_undo_log_truncate=ON
if trx_rseg_t::needs_purge indicates that all history has been purged.

Tested by: Matthias Leich

The array my_unicase_pages_unicode520[7] erroneously mapped to plane06
instead of plane07.

- rollback_inplace_alter_table() locks the fts internal tables.
At the time, insert tries to fetch the doc id from config table,
fails to lock the config table and returns doc id as 0.

fts_cmp_set_sync_doc_id(): Retry to fetch the doc id again if
it encounter DB_LOCK_WAIT_TIMEOUT error

- match()+0 returns the floating result and converts into integer value
and it leads to sporadic failure.

The initial issue was in assertion failure, which checked the equality
of lock to cancel with trx->lock.wait_lock in lock_sys_t::cancel().

If we analyze lock_sys_t::cancel() code from the perspective of
trx->lock.wait_lock racing, we won't find the error there, except the
cases when we need to reload it after the corresponding latches
acquiring.

So the fix is just to remove the assertion and reload
trx->lock.wait_lock after acquiring necessary latches.

Reviewed by: Marko Mäkelä <marko.makela@mariadb.com>

This is a partial revert of
commit 8b6a308e (MDEV-29883)
and a follow-up to the
merge commit 394fc71f (MDEV-24569).

The latching order related to any operation that accesses the allocation
metadata of an InnoDB index tree is as follows:

1. Acquire dict_index_t::lock in non-shared mode.
2. Acquire the index root page latch in non-shared mode.
3. Possibly acquire further index page latches. Unless an exclusive
dict_index_t::lock is held, this must follow the root-to-leaf,
left-to-right order.
4. Acquire a *non-shared* fil_space_t::latch.
5. Acquire latches on the allocation metadata pages.
6. Possibly allocate and write some pages, or free some pages.

btr_get_size_and_reserved(), dict_stats_update_transient_for_index(),
dict_stats_analyze_index(): Acquire an exclusive fil_space_t::latch
in order to avoid a deadlock in fseg_n_reserved_pages() in case of
concurrent access to multiple indexes sharing the same "inode page".

fseg_page_is_allocated(): Acquire an exclusive fil_space_t::latch
in order to avoid deadlocks. All callers are holding latches
on a buffer pool page, or an index, or both.
Before commit edbde4a1 (MDEV-24167)
a third mode was available that would not conflict with the shared
fil_space_t::latch acquired by ha_innobase::info_low(),
i_s_sys_tablespaces_fill_table(),
or i_s_tablespaces_encryption_fill_table().
Because those calls should be rather rare, it makes sense to use
the simple rw_lock with only shared and exclusive modes.

fil_crypt_get_page_throttle(): Avoid invoking fseg_page_is_allocated()
on an allocation bitmap page (which can never be freed), to avoid
acquiring a shared latch on top of an exclusive one.

mtr_t::s_lock_space(), MTR_MEMO_SPACE_S_LOCK: Remove.

buf_pool_t::watch_set(): Always buffer-fix a block if one was found,
no matter if it is a watch sentinel or a buffer page. The type of
the block descriptor will be rechecked in buf_page_t::watch_unset().
Do not expect the caller to acquire the page hash latch. Starting with
commit bd5a6403 it is safe to release
buf_pool.mutex before acquiring a buf_pool.page_hash latch.

buf_page_get_low(): Adjust to the changed buf_pool_t::watch_set().

This simplifies the logic and fixes a bug that was reproduced when
using debug builds and the setting innodb_change_buffering_debug=1.

buf_read_page_low(): Map the buf_page_t::read_complete() return
value DB_FAIL to DB_PAGE_CORRUPTED. The purpose of the DB_FAIL
return value is to avoid error log noise when read-ahead brings
in an unused page that is typically filled with NUL bytes.

If a synchronous read is bringing in a corrupted page where the
page frame does not contain the expected tablespace identifier and
page number, that must be treated as an attempt to read a corrupted
page. The correct error code for this is DB_PAGE_CORRUPTED.
The error code DB_FAIL is not handled by row_mysql_handle_errors().

This was missed in commit 0b47c126
(MDEV-13542).

This almost completely reverts
commit acd23da4 and
retains a safe optimization:

recv_sys_t::parse(): Remove any old redo log records for the
truncated tablespace, to free up memory earlier.
If recovery consists of multiple batches, then recv_sys_t::apply()
will must invoke recv_sys_t::trim() again to avoid wrongly
applying old log records to an already truncated undo tablespace.

WITH TIES would not take effect if SELECT DISTINCT was used in a
context where an INDEX is used to resolve the ORDER BY clause.

WITH TIES relies on the `JOIN::order` to contain the non-constant
fields to test the equality of ORDER BY fiels required for WITH TIES.

The cause of the problem was a premature removal of the `JOIN::order`
member during a DISTINCT optimization. This lead to WITH TIES code assuming
ORDER BY only contained "constant" elements.

Disable this optimization when WITH TIES is in effect.

(side-note: the order by removal does not impact any current tests, thus
it will be removed in a future version)

Reviewed by: monty@mariadb.org

There was a bug in JOIN::make_notnull_conds_for_range_scans() when
clearing TABLE->tmp_set, which was used to mark fields that could not be
null.

This function was only used if 'not_null_range_scan=on' is set.

The effect was that tmp_set contained a 'random value' and this caused
the optimizer to think that some fields could not be null.
FLUSH TABLES clears tmp_set and because of this things worked temporarily.

Fixed by clearing tmp_set properly.

Very minor hits found by Coverity for the S3 engine.

- cmp_rec_rec_simple() fails to detect duplicate key error for
bulk insert operation

- InnoDB fails to reset the after_apply variable before applying
the redo log in last batch during multi-batch recovery.

- During non-last batch of multi-batch recovery, InnoDB holds
log_sys.mutex and preallocates the block which may intiate
page flush, which may initiate log flush, which requires
log_sys.mutex to acquire again. This leads to assert failure.
So InnoDB recovery should release log_sys.mutex before
preallocating the block.

The tests expect the SIGNAL to not be cleared. Thus set NO_CLEAR_EVENT
within DBUG_EXECUTE_IF

As requested to the UN the country formerly known as Turkey is
to be refered to as Türkiye.

Reviewer: Alexander Barkov

MDEV-30608: rpl.rpl_delayed_parallel_slave_sbm sometimes fails with Seconds_Behind_Master should not have used second transaction timestamp

One of the constraints added in the MDEV-29639 patch, is that only
the first event after idling should update last_master_timestamp;
and as long as the replica has more events to execute, the variable
should not be updated. The corresponding test,
rpl_delayed_parallel_slave_sbm.test, aims to verify this; however,
if the IO thread takes too long to queue events, the SQL thread can
appear to catch up too fast.

This fix ensures that the relay log has been fully written before
executing the events.

Note that the underlying cause of this test failure needs to be
addressed as a bug-fix, this is a temporary fix to stop test
failures. To track work on the bug-fix for the underlying issue,
please see MDEV-30619.

The parser code for single-table DELETE missed the call of the function
LEX::check_main_unit_semantics(). As a result the the field nested level
of SELECT_LEX structures remained set 0 for all non-top level selects.
This could lead to different kind of problems. In particular this did not
allow to determine properly the selects where set functions had to be
aggregated when they were used in inner subqueries.

Approved by Oleksandr Byelkin <sanja@mariadb.com>

This patch is the result of running
run-clang-tidy -fix -header-filter=.* -checks='-*,modernize-use-equals-default' .

Code style changes have been done on top. The result of this change
leads to the following improvements:

1. Binary size reduction.
* For a -DBUILD_CONFIG=mysql_release build, the binary size is reduced by
  ~400kb.
* A raw -DCMAKE_BUILD_TYPE=Release reduces the binary size by ~1.4kb.

2. Compiler can better understand the intent of the code, thus it leads
   to more optimization possibilities. Additionally it enabled detecting
   unused variables that had an empty default constructor but not marked
   so explicitly.

   Particular change required following this patch in sql/opt_range.cc

   result_keys, an unused template class Bitmap now correctly issues
   unused variable warnings.

   Setting Bitmap template class constructor to default allows the compiler
   to identify that there are no side-effects when instantiating the class.
   Previously the compiler could not issue the warning as it assumed Bitmap
   class (being a template) would not be performing a NO-OP for its default
   constructor. This prevented the "unused variable warning".