Modify the join optimizer to specifically try to produce join orders that
can short-cut their execution for ORDER BY..LIMIT clause.

The optimization is controlled by @@optimizer_join_limit_pref_ratio.
Default value 0 means don't construct short-cutting join orders.
Other value means construct short-cutting join order, and prefer it only
if it promises speedup of more than #value times.

In Optimizer Trace, look for these names:
* join_limit_shortcut_is_applicable
* join_limit_shortcut_optimization
* limit_shortcut_choice

Added comments
Moved a part into find_indexes_matching_order().

FreeBSD doesn't like it and hangs.

As we don't wait for signal handler, let's disable SIGHUP in bootstrap
too

.opt files, unlike combinations, accumulate, let's not overuse them

followup for 13663cb5

Makes easier to add new policy to the list, and merge to newer versions-

Workaround patch: Do not remove GROUP BY clause when it has
subquer(ies) in it.

remove_redundant_subquery_clauses() removes redundant GROUP BY clause
from queries in form:
  expr IN (SELECT no_aggregates GROUP BY ...)
  expr {CMP} {ALL|ANY|SOME} (SELECT no_aggregates GROUP BY ...)
This hits problems when the GROUP BY clause itself has subquer(y/ies).

This patch is just a workaround: it disables removal of GROUP BY clause
if the clause has one or more subqueries in it.

Tests:
- subselect_elimination.test has all known crashing cases.
- subselect4.result, insert_select.result are updated.
Note that in some cases results of SELECT are changed too (not just
EXPLAINs). These are caused by non-deterministic SQL: when running a
query like:

  x > ANY( SELECT col1 FROM t1 GROUP BY constant_expression)

without removing the GROUP BY, the executor is free to pick the value
of t1.col1 from any row in the GROUP BY group (denote it $COL1_VAL).
Then, it computes x > ANY(SELECT $COL1_VAL).

When running the same query and removing the GROUP BY:

   x > ANY( SELECT col1 FROM t1)

the executor will actually check all rows of t1.

The problem was two fold:
- REPAIR TABLE t1 USE_FRM did not work for transactional
  Aria tables (Table was thought to be repaired, which it was not) which
  caused issues in later usage of the table.
- When swapping tmp_data file to data file, sort_info files where not
  updated. This caused problems if there was several unique keys and
  there was a duplicate for the second key.

Due to this bug a wrong result might be expected from queries with
an IN subquery predicate in the WHERE clause and a derived table in the
FROM clause to which split optimization could be applied.

The function JOIN::fix_all_splittings_in_plan() used the value of the
bitmap JOIN::sjm_lookup_tables() such as it had been left after the
search for the best plan for the select containing the splittable
derived table. That value could not be guaranteed to be correct. So the
recalculation of this bitmap is needed to exclude the plans with key
accesses from SJM lookup tables.

Approved by Igor Babaev <igor@maridb.com>

Otherwise spider_direct_sql may still think the spider plugin is
available even after spider_db_done() was called.

Revert "MDEV-19949 mariabackup option of '--password' or '-p' without specifying password in commandline"

This reverts commit 91fb8b7f.

Incompatible change, see tests in the next commit

Additional changes for the galera_vote_rejoin_ddl test (for 10.5+).
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>

The spider suite should --source include/start_slave.inc to make sure
the slave is up before proceeding.

When running on macOS, MTR will ask the operating system for the core count when --parallel=auto

cnt counter was incremented one extra time per line

safety first - tell mariadb client not to execute dangerous
cli commands, they cannot be present in the dump anyway.

wrapping the command in /*!999999 ..... */ guarantees that
if a non-mariadb-cli client loads the dump and sends it to the
server - the server will ignore the command it doesn't understand

mysql --sandbox

disables system (\!), tee (\T), pager with an argument(\P foo), source (\.)

does *not* disable edit (\e). Use EDITOR=/bin/false to disable
or, for example, EDITOR=rnano for something more useful

does *not* disable pager (\P) without an argument. Use
PAGER=cat or, for example PAGER=less LESSSECURE=1 for something
more useful

using a disabled command is an error, which can be ignored with --force

Also, a "sandbox" command (\-) - enables the sandbox mode until EOF
(current file or the session, if interactive)

the client is C++, use a much more concise C++ syntax

as a bonus, arguments that are used, are no longer marked "unused"

on disable_indexes(HA_KEY_SWITCH_NONUNIQ_SAVE) the engine does
not know that the long unique is logically unique, because on the
engine level it is not. And the engine disables it,

Change the disable_indexes/enable_indexes API. Instead of the enum
mode, send a key_map of indexes that should be enabled. This way the
server will decide what is unique, not the engine.

- This is a merge of commit f378e764
from 10.4 to 10.5.

This commit fixes sporadic failures in galera_3nodes_sr.GCF-336
test. The following changes have been made here:

1) A small addition to the test itself which should make
   it more deterministic by waiting for non-primary state
   before COMMIT;
2) More careful handling of the wsrep_ready variable in
   the server code (it should always be protected with mutex).

No additional tests are required.

followup for c5896384

dgcov.pl was putting gcov execution counters on wrong lines
in the report (*.dgcov files were correct), because it was
incrementing the new line number for diff lines starting from '-'
(lines from the old file, not present in the new)

* remove dead code
* simplify the check for table->s->next_number_index
* misc

MDEV-29345 update case insensitive (large) unique key with insensitive change of value - duplicate key

use collation-sensitive comparison when comparing fields