In the asynchronous I/O interface, InnoDB is invoking io_getevents()
with a timeout value of half a second, and requesting exactly 1 event
at a time.

The reason to have such a short timeout is to facilitate shutdown.

We can do better: Use an infinite timeout, wait for a larger maximum
number of events. On shutdown, we will invoke io_destroy(), which
should lead to the io_getevents system call reporting EINVAL.

my_getevents(): Reimplement the libaio io_getevents() by only invoking
the system call. The library implementation would try to elide the
system call and return 0 immediately if aio_ring_is_empty() holds.
Here, we do want a blocking system call, not 100% CPU usage. Neither
do we want the aio_ring_is_empty() trigger SIGSEGV because it is
dereferencing some memory that was freed by io_destroy().

The greedy fetch_add(1) approach of read_trylock() may cause
starvation of a waiting write lock request. Let us use a
compare-and-swap for the read lock acquisition in order to
guarantee the progress of writers.

Since commit 30ea63b7
we actually depend on futex on Linux. Also, we depend on
std::atomic for even longer.

We always defined PFS_SKIP_BUFFER_MUTEX_RWLOCK, that is,
the latches of the buffer pool blocks were never instrumented
in PERFORMANCE_SCHEMA.

For some reason, the debug_latch (which enforce proper usage of
buffer-fixing in debug builds) was instrumented.

In commit bf3c862f we introduced
an assertion that may dereference a null pointer.

This regression was caught by running the following:
./mtr --parallel=auto --suite=innodb \
--mysqld=--loose-innodb-adaptive-hash-index

The adaptive hash index is disabled by default since
commit 88cdfc5c (MDEV-20487)
and hence the problem was not caught earlier.

The test seems to deterministically fail on RelWithDebInfo builds
due to a timeout in wait_condition.inc.

According to Matthias Leich (the original author of the test),
the failure rate would reduce if we disabled the purge of
transaction history by setting innodb_force_recovery=2.

For now, let us run this stress test on debug builds only.

fil_space_t::flush_low(): Define and declare without inline.

ut_is_2pow(): Remove UNIV_LIKELY. This is almost exclusively
used in debug assertions. UNIV_LIKELY is not compatible with
static_assert in some compilers.

pipeline in community BB

Fix for rebuild from source step

Disable MCS on i386|i686 platforms

This patch puts MCS debian packaging files and part of debian/control
into the engine directory

Centos/RHEL7 have the MAP_HUGE_SHIFT constant
defined in linux/mman.h which needed to get included.

When MDEV-19544 (commit 1a6f4704)
simplified the initialization of the local variable
set_also_gap_locks, an inadvertent change was included.
Essentially, all code branches that are executed when
set_also_gap_locks hold must also ensure that
trx->isolation_level > TRX_ISO_READ_COMMITTED holds.
This was being violated in a few code paths.

It turns out that there is an even simpler fix: Remove the test
of thd_is_select() completely. In that way, the first part of
UPDATE or DELETE should work exactly like SELECT...FOR UPDATE.

thd_is_select(): Remove.

Starting with commit 7cffb5f6 (MDEV-23399)
the function buf_flush_page() will first acquire block->lock and only
after that invoke set_io_fix(). Before that, it was possible to reach
a livelock between buf_page_create() and buf_flush_page().

buf_page_create(): Directly try acquiring the exclusive page latch
without checking whether the page is io-fixed or buffer-fixed.
(As a matter of fact, the have_x_latch() check is not strictly necessary,
because we still support recursive X-latches.)
In case of a latch conflict, wait while allowing buf_page_write_complete()
to acquire buf_pool.mutex and release the block->lock.

An attempt to wait for exclusive block->lock while holding buf_pool.mutex
would lead to a hang in the tests parts.part_supported_sql_func_innodb
and stress.ddl_innodb, due to a deadlock between buf_page_write_complete()
and buf_page_create().

Similarly, in case of an I/O fixed compressed-only
ROW_FORMAT=COMPRESSED page, we will sleep before retrying.

In both cases, we will sleep for 1ms or until a flush batch is completed.

The data member tv_usec of the struct timeval is declared as suseconds_t
on MacOS. Size of suseconds_t is 4 bytes. On the other hand, size of ulong
is 8 bytes on 64-bit MacOS, so attempt to assign a value of wider type
(usec) to a value (tv_usec) of narrower type leads to error.

MDEV-23610: Slave user can't run "SHOW SLAVE STATUS" anymore after upgrade to 10.5, mysql_upgrade should take of that

Post push fix. Update version to 10.5.8.

This allows MariaDB to compile on old (limits to >2.6.32)
linux kernel versions.

This warns that attempts to use large pages will rely on
implict kernel determination.

This reverts commit 6cf8f05f.

Original patch assumed that MAP_HUGETLB as consistent across
achitectures which isn't the case. Defining it unconditionally
broke large pages on every achitecutre where the value differed
from x86_64.

With the EOL for Centos/RHEL6 announced in 10.5.7, <3.8 linux
kernels are no longer supported.

Account for variety of mips, hppa, solaris and other messages.

Copied from rpl.rpl_drop_db test.

MDEV-23610: Slave user can't run "SHOW SLAVE STATUS" anymore after upgrade to 10.5, mysql_upgrade should take of that

Fixing a post push test issue.

MDEV-23610: Slave user can't run "SHOW SLAVE STATUS" anymore after upgrade to 10.5, mysql_upgrade should take of that

Add a new privilege "SLAVE MONITOR" which will grant user the permission
to execute "SHOW SLAVE STATUS" and "SHOW RELAYLOG EVENTS" commands.

SHOW SLAVE STATUS requires either SLAVE MONITOR/SUPER
SHOW RELAYLOG EVENTS requires SLAVE MONITOR privilege.

into the engine directory

remove version data from the test output

The fix of MDEV-23456 (commit b1009ae5)
introduced a livelock between page flushing and a thread that is
executing buf_page_create().

buf_page_create(): If the current mini-transaction is holding
an exclusive latch on the page, do not attempt to acquire another
one, and do not care about any I/O fix.

mtr_t::have_x_latch(): Replaces mtr_t::get_fix_count().

dyn_buf_t::for_each_block(const Functor&) const: A new variant.

rw_lock_own(): Add a const qualifier.

Reviewed by: Thirunarayanan Balathandayuthapani

Due to a premature cleanup of the unit that specified a recursive CTE
used in the second operand of union the server fell into an infinite
loop in the reported test case. In other cases this premature cleanup
could cause other problems.
The bug is the result of a not quite correct fix for MDEV-17024. The
unit that specifies a recursive CTE has to be cleaned only after the
cleanup of the last external reference to this CTE. It means that
cleanups of the unit triggered not by the cleanup of a external
reference to the CTE must be blocked.
Usage of local table chains in selects to get external references to
recursive CTEs was not correct either because of possible merges of
some selects.

Also fixed a minor bug in st_select_lex::set_explain_type() that caused
typing 'RECURSIVE UNION' instead of 'UNION' in EXPLAIN output for external
references to a recursive CTE.