This should be equivalent to pull request #1889 by Krunal Bauskar.

The existing logic in purge_coordinator_state::do_purge()
activates a number of the configured innodb_purge_threads
based on the history list length. Activating more purge worker
tasks should shrink the history list faster. But, more purge
workers will also generate more redo log, which may slow down
writes by user connections.

row_purge_parse_undo_rec(): Revert the work-around that was added in
commit 46904424.

purge_coordinator_state: Keep track of the redo log fill factor
(how big percentage of innodb_log_file_size is being occupied by
log records that were generated since the latest checkpoint).
If the redo log is getting full, log checkpoints will be triggered
more frequently, and user threads may end up waiting in
log_free_check(). We try to reduce purge-induced jitter in overall
throughput by throttling down the active number of purge tasks as
the log checkpoint age is approaching the log size (in other words,
the redo log fill factor is approaching 100%).

purge_coordinator_timer_callback(): Remove. We will have
purge_coordinator_timer invoke purge_coordinator_callback()
directly.

srv_master_callback(): Invoke srv_wake_purge_thread_if_not_active()
instead of purge_coordinator_timer_callback(). That is, we will
trigger purge_coordinator_callback() once per second if there is
any work to be done.

purge_state::do_purge(): Replaces srv_do_purge(),
purge_coordinator_callback_low(), and
purge_coordinator_timer_callback(). The static variables
inside srv_do_purge() were moved to purge_state data members.

In commit ff5d306e we removed
dbug_after_task_callback but forgot to revert the rest of
commit bada05a8.

row_purge_remove_clust_if_poss_low(): The table identified by
SYS_INDEXES.TABLE_ID is protected by exclusive dict_sys.latch.
There is no need to touch its reference count.

# Conflicts:
#	appveyor.yml

# Conflicts:
#	appveyor.yml

# Conflicts:
#	cmake/os/Windows.cmake
#	sql/sql_yacc.yy

A conversion warning 4267 that we want to disable(prior to 10.3),
was suppressed with  cmake VS generator for C++ and C, despite being set
only for CXX flags.

The fix is to disable the warning in C flags, too. In 10.2, this warning
is noisy, in 10.3 it is fixed.

instead, include handler_rollback in the following per-connection selects

The merge accidentally
omitted the 10.4 commit 472b35c7 and
reverted the 10.5 commit 6e3bd663.

No need to run through all system checks, we already know
it is not possible to authenticate with AF_UNIX socket.

Apply 115fec58 to 10.5

The st_blksize returned by fstat(2) is not documented to be
a power of 2, like we assumed in
commit 58252fff (MDEV-26040).
While on Linux, the st_blksize appears to report the file system
block size (which hopefully is not smaller than the sector size
of the underlying block device), on FreeBSD we observed
st_blksize values that might have been something similar to st_size.

Also IBM AIX was affected by this. A simple test case would
lead to a crash when using the minimum innodb_buffer_pool_size=5m
on both FreeBSD and AIX:

seq -f 'create table t%g engine=innodb select * from seq_1_to_200000;' \
1 100|mysql test&
seq -f 'create table u%g engine=innodb select * from seq_1_to_200000;' \
1 100|mysql test&

We will fix this by not trusting st_blksize at all, and assuming that
the smallest allowed write size (for O_DIRECT) is 4096 bytes. We hope
that no storage systems with larger block size exist. Anything larger
than 4096 bytes should be unlikely, given that it is the minimum
virtual memory page size of many contemporary processors.

MariaDB Server on Microsoft Windows was not affected by this.

While the 512-byte sector size of the venerable Seagate ST-225 is still
in widespread use, the minimum innodb_page_size is 4096 bytes, and
innodb_log_file_size can be set in integer multiples of 65536 bytes.

The only occasion where InnoDB uses smaller data file block sizes than
4096 bytes is with ROW_FORMAT=COMPRESSED tables with KEY_BLOCK_SIZE=1
or KEY_BLOCK_SIZE=2 (or innodb_page_size=4096). For such tables,
we will from now on preallocate space in integer multiples of 4096 bytes
and let regular writes extend the file by 1024, 2048, or 3072 bytes.

The view INFORMATION_SCHEMA.INNODB_SYS_TABLESPACES.FS_BLOCK_SIZE
should report the raw st_blksize.

For page_compressed tables, the function fil_space_get_block_size()
will map to 512 any st_blksize value that is larger than 4096.

os_file_set_size(): Assume that the file system block size is 4096 bytes,
and only support extending files to integer multiples of 4096 bytes.

fil_space_extend_must_retry(): Round down the preallocation size to
an integer multiple of 4096 bytes.

Cover all columns that did not have comments. Adjust docs based off of
MariaDB implementation.

Improve documentation of performance_schema tables by appending COLUMN
comments to tables. Additionally improve test coverage and update corresponding
tests.

This is part of the patch covering newer columns and tables in 10.5.

FTS indexes has a prefix_len=1 or prefix_len=0 as stated by comment in
mysql_prepare_create_table().

Thus, a newly added assertion should be relaxed for FTS indexes.

With this patch, 4-component MSI version can be used, e.g by setting
TINY_VERSION variable in CMake, or by adding a string, e.g
MYSQL_VERSION_EXTRA=-2
which sets TINY_VERSION to 2, and also changes the package name.

The 4-component MSI versions do not support MSI major upgrades, only minor
ones, i.e do not reinstall components, just update existing ones based
on versioning rules.

To support these rules, add DefaultVersion for the files that won't
otherwise be versioned - headers, static and import libraries,
pdbs, text - xml, python and perl scripts Also silence WiX warning
that MSI won't store hashes for those files anymore.