1. Code simplification:

Item_default_value handled all these values:
a. DEFAULT(field)
b. DEFAULT
c. IGNORE
and had various conditions to distinguish (a) from (b) and from (c).

Introducing a new abstract class Item_contextually_typed_value_specification,
to handle (b) and (c), so the hierarchy now looks as follows:

Item
  Item_result_field
    Item_ident
      Item_field
        Item_default_value                      - DEFAULT(field)
  Item_contextually_typed_value_specification
    Item_default_specification                  - DEFAULT
    Item_ignore_specification                   - IGNORE

2. Introducing a new virtual method is_evaluable_expression() to
determine if an Item is:
- a normal expression, so its val_xxx()/get_date() methods can be called
- or a just an expression substitute, whose value methods cannot be called.

3. Disallowing Items that are not evalualble expressions in table value
   constructors.

my_is_2pow is only used on linux.

fixes compile warning:

mysys/my_largepage.c:48:23: warning: unused function 'my_is_2pow' [-Wunused-function]

static inline my_bool my_is_2pow(size_t n) { return !((n) & ((n) - 1)); }

                      ^

1 warning generated.

TIME_ZONE_ID_UNKNOWN return code from GetDynamicTimeZoneInformation()
does not mean failure.

It only means, daylight saving dates in the returned strct are not valid.
TIME_ZONE_ID_INVALID means failure, in this case  "unknown" should be returned

In multithreaded build (at least confirmed with Windows ninja and msbuild),
at the end of "sql" target compilation, only 2 processors are used,
compiling either sql_yacc.cc or sql_yacc_ora.cc.
Thus, link of dependent executables or libraries is delayed while build is
underusing the CPU.

Rearrange the source list to improve  parallelism.

Liposuction of about 20% package size is achieved by using
linker /OPT:REF,ICF and compile option /Gw

Use STRING(APPEND VAR...) rather than SET(VAR "${VAR} ..."), it is shorter

In the merge 9e6e4355
we made Atomic_counter a more generic wrapper of std::atomic
so that dict_index_t would support the implicit assignment operator.

It is better to revert the changes to Atomic_counter and
instead introduce Atomic_relaxed as a generic wrapper to std::atomic.

Unlike Atomic_counter, we will not define operator++, operator+=
or similar, because we want to make the operations more explicit
in the users of Atomic_wrapper, because unlike loads and stores,
atomic read-modify-write operations always incur some overhead.

Enable tests with additional galera output to find out actual
reason for test failures.

In commit ad6171b9 (MDEV-22456)
we removed the acquisition of the adaptive hash index latch
from the caller of btr_search_update_hash_ref().
The tests innodb.innodb_buffer_pool_resize_with_chunks
and innodb.innodb_buffer_pool_resize
would occasionally fail starting with 10.3,
due to MDEV-12288 causing more purge activity during the test.

btr_search_update_hash_ref(): After acquiring the adaptive hash index
latch, check that the adaptive hash index is still enabled on the page.

The problem is caused by the operation of netcat streamer and does
not appear on systems where socat is installed. We need to add the
"-N" option for netcat to call shutdown() on the socket when receiving
EOF from STDIN.

The problem is caused by the operation of netcat streamer and does
not appear on systems where socat is installed. We need to add the
"-N" option for netcat to call shutdown() on the socket when receiving
EOF from STDIN.

The problem is caused by the operation of netcat streamer and does
not appear on systems where socat is installed. We need to add the
"-N" option for netcat to call shutdown() on the socket when receiving
EOF from STDIN.

The problem is caused by the operation of netcat streamer and does
not appear on systems where socat is installed. We need to add the
"-N" option for netcat to call shutdown() on the socket when receiving
EOF from STDIN.

Localhost, depending on the platform can return any
127.0.0.1/8 address.

Also clean away dead code that is not used and will never have any use
on the 10.2 branch.

There is a 4 MB hard limit on Travis-CI and build output needs to be less
than that. Silencing the 'make install' step gets rid of a lot of
"Installing.." and "Missing.." and removing all mysql-test files will
make the dh_missing warnings much shorter.

Cherry-picked from 41952c85.

Backported from 30b44aae.

The issue here is that end_of_file for encrypted temporary IO_CACHE (used by filesort) is updated
using lseek.
Encryption adds storage overhead and hides it from the caller by recalculating offsets and lengths.
Two different IO_CACHE cannot possibly modify the same file
because the encryption key is randomly generated and stored in the IO_CACHE.
So when the tempfiles are encrypted DO NOT use lseek to change end_of_file.

Further observations about updating end_of_file using lseek
1) The end_of_file update is only used for binlog index files
2) The whole point is to update file length when the file was modified via a different file descriptor.
3) The temporary IO_CACHE files can never be modified via a different file descriptor.
4) For encrypted temporary IO_CACHE, end_of_file should not be updated with lseek

Problem:
=======
  - During alter rebuild, document read from old table is tokenzied
parallelly by innodb_ft_sort_pll_degree threads and stores it
in respective merge files. While doing the parallel merge, InnoDB
wrongly skips the root level selection of merging buffer records.
So it leads to insertion of merge records in non-ascending order.

Solution:
==========
  Build selection tree for the root level also. So that root of
selection tree can always contain sorted buffer.

This test was disabled in a135f0ab, but
accidentally reverted during the merge in
https://github.com/MariaDB/server/compare/0186b0a07760...b30a01314217

Because it was a 3-way merge, the removal is not directly visible.
It can be verified manually though:

  Line not changed:
  git diff a135f0ab..0186b0a0 mysql-test/unstable-tests

  Line removed:
  git diff a135f0ab..b30a0131 mysql-test/unstable-tests


This commit fixes the Travis-CI build and makes the main 10.5 git branch
green again on Travis-CI (and whatever else build environment that also
is failing due to this test).

Related: MDEV-22592

The buildbot.askmonty.org has explicit tests that check that this file
exists, thus to get tests pass, an empty placeholder must be created.
Remove this once CI has been updated not to expect this file.

We can't expect that users want to always convert their mysqld_safe
settings on an upgrade. In its current form it will always run, and that
seems unnecessary on every single installation.

Also the script is buggy, leaks mysqld_safe output into the written file
and since it gets syntax errors the whole mariadb.service will fail to
work.

These do now show up automatically due to init and systemd customizations,
so the handiest fix is to add them manually. This has been the praxis
in downstream MariaDB packaging for a couple years now, and works fine.

- Ensure service is loaded and started after installation,
  (fixes service start issues in Debian/Ubuntu upgrades where
  otherwise service mysql status stayed stopped)

- Ensure service stopped before removal/purge
  (fixes unstopped processes detected by piuparts)

- Ensure systemd daemon is reloaded after removal/purge when service
  has been removed

Partially reverts commit a4cc6fb9.

While all current versions of Linux have systemd, support for traditional
init.d is still needed e.g. on Linux subsystem on Windows, kFreeBSD and
special variants of Debian/Ubuntu that for other reasons don't have
systemd.

Thus, re-introduce the init file that was remove, but this time with
then name 'mariadb'.

Supporting traditional sysv init in paraller with systemd is easy, since
Debian has facilities for it.

Also simplify and update salsa-ci.yml install/upgrade testing works
for all previous MariaDB and MySQL releases without any excess quirks.

Note that in fresh installs the salsa-ci.yml needs to run command
'service mariadb status' to control the service, while on upgrades
it is enough to run 'service mysql status', since the init.d/mysql
file is left behind from previous install, along with some other
config files such as /etc/default/mysql and /etc/mysql/* stuff.

Also, adding 10.2 related changes for MDEV-22579

We will expose some more std::atomic internals in Atomic_counter,
so that dict_index_t::lock will support the default assignment operator.