When InnoDB is extending a data file, it is updating the FSP_SIZE
field in the first page of the data file.

In commit 8451e090 (MDEV-11556)
we removed a work-around for this bug and made recovery stricter,
by making it track changes to FSP_SIZE via redo log records, and
extend the data files before any changes are being applied to them.

It turns out that the function fsp_fill_free_list() is not crash-safe
with respect to this when it is initializing the change buffer bitmap
page (page 1, or generally, N*innodb_page_size+1). It uses a separate
mini-transaction that is committed (and will be written to the redo
log file) before the mini-transaction that actually extended the data
file. Hence, recovery can observe a reference to a page that is
beyond the current end of the data file.

fsp_fill_free_list(): Initialize the change buffer bitmap page in
the same mini-transaction.

The rest of the changes are fixing a bug that the use of the separate
mini-transaction was attempting to work around. Namely, we must ensure
that no other thread will access the change buffer bitmap page before
our mini-transaction has been committed and all page latches have been
released.

That is, for read-ahead as well as neighbour flushing, we must avoid
accessing pages that might not yet be durably part of the tablespace.

fil_space_t::committed_size: The size of the tablespace
as persisted by mtr_commit().

fil_space_t::max_page_number_for_io(): Limit the highest page
number for I/O batches to committed_size.

MTR_MEMO_SPACE_X_LOCK: Replaces MTR_MEMO_X_LOCK for fil_space_t::latch.

mtr_x_space_lock(): Replaces mtr_x_lock() for fil_space_t::latch.

mtr_memo_slot_release_func(): When releasing MTR_MEMO_SPACE_X_LOCK,
copy space->size to space->committed_size. In this way, read-ahead
or flushing will never be invoked on pages that do not yet exist
according to FSP_SIZE.

commit 854c219a (MDEV-17301)
broke a constraint: Fixed-length columns cannot be extended in InnoDB
without rebuilding the table.

ha_innobase::can_convert_string(): Correct the condition. We must
not allow any instantaneous change to the length of CHAR columns
measured in characters. For any format other than ROW_FORMAT=REDUNDANT,
we can allow the length in bytes to be extended if mbminlen<mbmaxlen held
before the change of the character set.

m_file[0] not always is a good sample.

Server auto-sets lower_case_file_system value based on default
datadir's behavior instead of instead of using the directory specified
by the user through the configuration file or command line options.

This patch fixes this problem.

Server auto-sets lower_case_file_system value based on default
datadir's behavior instead of instead of using the directory specified
by the user through the configuration file or command line options.

This patch fixes this problem.

In commit 0f90728b (MDEV-16809)
we introduced the configuration option innodb_log_optimize_ddl
for controlling whether native index creation or table-rebuild
in InnoDB should avoid writing full redo log.

Fungo Wang reported that this option is causing occasional failures.
The reason is that pages may be written to data files in an
inconsistent state. Applying log records to such inconsistent pages
may fail.

The solution is to always invoke PageBulk::finish() before page latches
may be released, to ensure that the page contents is in a consistent
state.

Something similar was implemented in MySQL 8.0.13:
mysql/mysql-server@d1254b947354e0f5b7223b09c521bd85f22e1e31

buf_block_t::skip_flush_check: Remove. Suppressing consistency checks
is a bad idea.

PageBulk::needs_finish(): New predicate: Determine whether
PageBulk::finish() must fix up the page.

PageBulk::init(): Clear PAGE_DIRECTION to ensure that needs_finish()
will hold. We change the field from PAGE_NO_DIRECTION to 0
and back without writing redo log. This trick avoids the need
to introduce any new data member to PageBulk.

PageBulk::insert(): Replace some high-level accessors to bypass
debug assertions related to PAGE_HEAP_TOP that we will be violating
until finish() has been executed.

PageBulk::finish(): Tolerate m_rec_no==0. We must invoke this also
on an empty page, to ensure that PAGE_HEAP_TOP is initialized.

PageBulk::commit(): Always invoke finish().

PageBulk::release(), BtrBulk::pageSplit(), BtrBulk::storeExt(),
BtrBulk::finish(): Invoke PageBulk::finish().

page_simple_validate_old(), page_simple_validate_new():
Require PAGE_N_DIR_SLOTS to be at least 2.

MDEV-22721 (commit eba2d10a)
inadvertently introduced an infinite loop.

page_validate(): Remove the infinite loop.

In fsp_path_to_space_name(), we would access a byte right before
the start of the string, tripping AddressSanitizer.

This reverts commit d87006a1
and commit a7634281.

-Wl,-z,relro,-z,now are linker flags and should
be checked as such.

TODO: perform module, exe shared checks separately
rather than a pure linker check.

An oveflow was happening on windows because on Windows sizeof(ulong) is 4 bytes
while it is 8 bytes on Linux.
Switched avg_frequency and avg length for column statistics to ulonglong.
Switched avg_frequency for index statistics to ulonglong.

This version is not optimized yet. It could have bugs because I didn't
check it with unit tests. Also, std::char_traits are not really supported.
So, now it's not possible to create f.ex. a case insensitive string_view.

fil_path_to_space_name(): renamed, moved to another file
and refactored to use string_view

The only InnoDB change between MySQL 5.7.30 and MySQL 5.7.31
that is applicable to MariaDB Server was applied in
commit 8d061996 (MDEV-23161).

The only InnoDB changes between Percona XtraDB Server 5.6.47-87.0
and 5.6.48-88.0 are related to InnoDB changes between MySQL 5.6.47
and MySQL 5.6.48, which we had already applied.

There were no InnoDB changes between MySQL 5.6.48 and MySQL 5.6.49.

This issue was originally reported by Fungo Wang, along with a fix, as
MySQL Bug #98990.

His suggested fix was applied as part of
mysql/mysql-server@a003fc373d1adb3ccea353b5d7d83f6c4c552383
and released in MySQL 5.7.31.

i_s_metrics_fill(): Add the missing call to Field::set_notnull(),
and simplify some code.

- i_s_fts_index_cache_fill() should take shared lock of fts cache
before accessing index cache to avoid reading stale data.

- Problem is that test case creates iblogfile* files. So existing
ibdata pages could point to future LSN. Fix is that taking the
backup of data before iblogfile* creation and apply it before
exiting the test case.

MDEV-22890 DEADLOCK of threads detected: row0sel.cc S-LOCK / btr0cur.cc S-LOCK / row0quiesce.cc X-LOCK

Problem:
=======
- Read operations are always allowed to hold a secondary index leaf
latch and then look up the corresponding clustered index record.
Flush table operation acquires secondary index latch while holding
a clustered index latch. It leads to deadlock violation.

Fix:
====
- Flush table operation should acquire secondary index before taking
clustered index to avoid deadlock violation with select operation.

Only install wsrep scripts and links if WSREP_ON is actually set

MDEV-22463: Element_type &Bounds_checked_array<Item *>::operator[](size_t) [Element_type = Item *]: Assertion `n < m_size' failed.

Allocate space for fields inside the window function (arguments, PARTITION BY and ORDER BY clause)
in the ref pointer array. All fields inside the window function are part of the temporary
table that is required for the window function computation.