incomplete. locking issues

because it is not

in particular, after checking for duplicates in a partitioned table,
do not re-check it for every partition individually

This patch removes support for LinuxThreads.
It was superseded by NPTL in Linux 2.6 (2003).

Problem:
=======
When we upgrade from "mysql" to "mariadb" if slave is using repositories as
tables their data is completely ignored and no warning is issued in error log.

Fix:
===
"mysql_upgrade" test should check for the presence of data in
"mysql.slave_master_info" and "mysql.slave_relay_log_info" tables. When tables
have some data the upgrade script should report a warning which hints users
that the data in repository tables will be ignored.

This task deals with packing the sort key inside the sort buffer, which  would
lead to efficient usage of the memory allocated for the sort buffer.

The changes brought by this feature are
  1) Sort buffers would have sort keys of variable length
  2) The format for sort keys inside the sort buffer would look like
     |<sort_length><null_byte><key_part1><null_byte><key_part2>.......|
      sort_length is the extra bytes that are required to store the variable
      length of a sort key.
  3) When packing of sort key is done we store the ORIGINAL VALUES inside
     the sort buffer and not the STRXFRM form (mem-comparable sort keys).
  4) Special comparison function packed_keys_comparison() is introduced
     to compare 2 sort keys.

This patch also contains contributions from Sergei Petrunia.

PageBulk::insertPage(): Check the array bounds before comparing.
We used to read one byte beyond the end of the 'rec' payload.
The incorrect logic was originally introduced in
commit 7ae21b18.

buf_flush_freed_page(): Reformat in the common style, and
simplify some code. Prefer to request all information from
smaller data structures (buf_page_t) than from fil_space_t
or the global variable srv_immediate_scrub_data_uncompressed.

SysTablespace::open_or_create(): Assert that the temporary
tablespace will not be created in page_compressed format, so that
buf_flush_freed_page() can avoid checking that on every call.

IORequest: Remove duplicated constructors, and do not explicitly
declare a default constructor.

Related to MDEV-21769.

Related to MDEV-21769.

After the '.so' one is supposed to use the directory name, like we have
correctly in all old man pages:
  mysql_client_test_embedded.1:.so man1/mysql_client_test.1
  mysql_embedded.1:.so man1/mysql.1
  mysqltest_embedded.1:.so man1/mysqltest.1

This change adds the 'man1/' component so the link has the correct format.
Actually using man links is a deprecated practice and using symlinks
would be better, but that can be fixed in a later commit.

From https://www.debian.org/doc/debian-policy/ch-docs.html#manual-pages:
> If one man page needs to be accessible via several names it is better
> to use a symbolic link than the .so feature

Detected via Lintian errors:
  E: mariadb-server-10.5: bad-so-link-within-manual-page usr/share/man/man1/mariadb-show.1.gz
  E: mariadb-client-10.5: bad-so-link-within-manual-page usr/share/man/man1/mariadb-binlog.1.gz
  E: mariadb-client-10.5: bad-so-link-within-manual-page usr/share/man/man1/mariadb-plugin.1.gz

Related to MDEV-21769.

This fixes errors like:

  $ LC_ALL=en_US.UTF-8 MANROFFSEQ='' MANWIDTH=80 \
    man --warnings -E UTF-8 -l -Tutf8 -Z mysql-test-run.pl.1 > /dev/null

  troff: <standard input>:246: warning [p 2, 6.0i, div '3tbd1,1', 0.3i]: can't break line
  troff: <standard input>:275: warning [p 2, 6.0i, div '3tbd6,1', 0.8i]: can't break line

Related to MDEV-21769.

Related to MDEV-21769.

Added CYCLE ... RESTRICT (nonstandard) clause to recursive CTE.

The following parameters are deprecated:

  innodb-background-scrub-data-uncompressed
  innodb-background-scrub-data-compressed
  innodb-background-scrub-data-interval
  innodb-background-scrub-data-check-interval

Removed scrubbing code completely(btr0scrub.h, btr0scrub.cc)
Removed information_schema.innodb_tablespaces_scrubbing tables
Removed the scrubbing logic from fil_crypt_thread()

When a InnoDB data file page is freed, its contents becomes garbage,
and any storage allocated in the data file is wasted. During flushing,
InnoDB initializes the page with zeros if scrubbing is enabled. If the
tablespace is compressed then InnoDB should punch a hole else ignore the
flushing of the freed page.

buf_page_t:
- Replaced the variable file_page_was_freed, init_on_flush in buf_page_t
with status enum variable.
- Changed all debug assert of file_page_was_freed to DBUG_ASSERT
of buf_page_t::status

Removed buf_page_set_file_page_was_freed(),
buf_page_reset_file_page_was_freed().

buf_page_free(): Newly added function which takes X-lock on the page
before marking the status as FREED. So that InnoDB flush handler can
avoid concurrent flush of the freed page. Also while flushing the page,
InnoDB make sure that redo log which does freeing of the page also written
to the disk. Currently, this function only marks the page as FREED if
it is in buffer pool

buf_flush_freed_page(): Newly added function which initializes zeros
asynchorously if innodb_immediate_scrub_data_uncompressed is enabled.
Punch a hole to the file synchorously if page_compressed is enabled.
Reset the io_fix to NORMAL. Release the block from flush list and
associated mutex before writing zeros or punch a hole to the file.

buf_flush_page(): Removed the unnecessary usage of temporary
variable "flush"

fil_io(): Introduce new parameter called punch_hole. It allows fil_io()
to punch the hole to the file for the given offset.

buf_page_create(): Let the callers assign buf_page_t::status.
Every caller should eventually invoke mtr_t::init().

fsp_page_create(): Remove the unused mtr_t parameter.

In all other callers of buf_page_create() except fsp_page_create(),
before invoking mtr_t::init(), invoke
mtr_t::sx_latch_at_savepoint() or mtr_t::x_latch_at_savepoint().

mtr_t::init(): Initialize buf_page_t::status also for the temporary
tablespace (when redo logging is disabled), to avoid assertion failures.

MDEV-21833 Make slave_run_triggers_for_rbr enforce triggers to run on slave, even when there are triggers on the master

A bit changed patch of Anders Karlsson with examples added.

New parameters "ENFORCE" to slave-run-triggers-for-rbr added.