This patch corrects the fix of the patch for mdev-19421 that resolved
the problem of parsing some embedded join expressions such as
  t1 join t2 left join t3 on t2.a=t3.a on t1.a=t2.a.
Yet the patch contained a bug that prevented proper context analysis
of the queries where such expressions were used together with comma
separated table references in from clauses.

MariaDB 10.4 was crashing when thread-handling was set to
pool-of-threads and wsrep was enabled.

There were two apparent reasons for the crash:
- Connection handling in threadpool_common.cc was missing calls to
  control wsrep client state.
- Thread specific storage which contains thread variables (THR_KEY_mysys)
  was not handled appropriately by wsrep patch when pool-of-threads
  was configured.

This patch addresses the above issues in the following way:
- Wsrep client state open/close was moved in thd_prepare_connection() and
  end_connection() to have common handling for one-thread-per-connection
  and pool-of-threads.
- Thread local storage handling in wsrep patch was reworked by introducing
  set of wsrep_xxx_threadvars() calls which replace calls to
  THD store_globals()/reset_globals() and deal with thread handling
  specifics internally.

Wsrep-lib was updated to version which relaxes internal concurrency
related sanity checks.

Rollback code from wsrep_rollback_process() was extracted to separate calls
for better readability.

Post rollback thread was removed as it was completely unused.

Mroonga does not build on Windows due to log_10_int being used
(indirectly) and n ot properly decorated with MYSQL_PLUGIN_IMPORT

The reason for hitting the assert is that rec_per_key estimates have some garbage value.
So the solution to fix this would be for long unique keys to use use rec_per_key for only 1 keypart,
that means rec_per_key[0] would have the estimate.

even if -DBUILD_SHARED_LIBS=ON was used

Added:
- "semijoin_strategy_choice" element (actions in advance_sj_state(), name
  matches the name in MySQL)

- semijoin_table_pullout element.

handlerton that is able to processes the whole query. For that it
traverses tables from subqueries.

Select_handler now cleans up temporary table structures on dctor call.

The MDEV-20265 commit e746f451
introduces DBUG_ASSERT(right_op == r_tbl) in
st_select_lex::add_cross_joined_table(), and that assertion would
fail in several tests that exercise joins. That commit was skipped
in this merge, and a separate fix of MDEV-20265 will be necessary in 10.4.

Current easy fix is not possible, because SELECT clones ha_partition
and then closes the clone which leads to unclosed transaction in
partitions we forcely prune out. We cound solve this by closing these
partitions (and release from transaction) in
change_partitions_to_open() at versioning conditions stage, but this
is problematic because table lock is acquired for each partition at
open stage and therefore must be released when we close partition
handler in change_partitions_to_open(). More details in MDEV-20376.

This should change after MDEV-20250 where mechanism of opening
partitions will be improved.

This reverts commit cdbac54d.

Fix debug build failing with error:

extended initializer lists only available with -std=c++11 or -std=gnu++11

ha_innobase::open(): Always ignore problems with FOREIGN KEY constraints
(pass DICT_ERR_IGNORE_FK_NOKEY), no matter whether foreign_key_checks
is enabled. Instead, we must report errors when enforcing the FOREIGN KEY
constraints. As a result of ignoring these errors, the tables will be
loaded with dict_foreign_t objects whose foreign_index or referenced_index
will be NULL.

Also, pass DICT_ERR_IGNORE_FK_NOKEY instead of DICT_ERR_IGNORE_NONE
to dict_table_open_on_id_low() in many other cases. Notably, on
CREATE TABLE and ALTER TABLE, we will keep validating the FOREIGN KEY
constraints as before.

dict_table_open_on_name(): If no other flags than
DICT_ERR_IGNORE_FK_NOKEY are set, refuse access to unreadable tables.
Some encryption tests rely on this code path.

For the DML code path, we used to have the problem that when
one of the indexes was missing in dict_foreign_t, we would ignore
the FOREIGN KEY constraint altogether. The following changes
address that.

row_ins_check_foreign_constraints(): Add the parameter pk.
For the primary key, consider also foreign key constraints for which
foreign->foreign_index=NULL (no underlying index is available).

row_ins_check_foreign_constraint(): Report errors also for !check_ref.
Remove a redundant check for srv_read_only_mode.

row_ins_foreign_report_add_err(): Tolerate foreign->foreign_index=NULL.

fkerr_t: Errors for the foreign key checks. Replaces ulint,
which used #define that looked like dberr_t literals.

wsrep_dict_foreign_find_index(): Remove. Use
dict_foreign_find_index() instead, with default parameters.

dict_foreign_push_index_error(): Do not add redundant quotes
around quoted table names.

Add wait conditions and compare cardinality etc information
between nodes and print something only if they differ.

heap_scan() makes info->next_block to be either an integer number
of share->block.records_in_block's or the total number of
records in the table. So when this total number or records changes,
info->next_block needs to be recalculated to take it into account.

This is a different fix for "Fixes a problem with heap when scanning and insert rows at the same time"

This reverts commit 262927a9.

Let us invoke wait_all_purged.inc right before the workload.
Starting with MDEV-12288 in MariaDB Server 10.3, also INSERT
generates purge workload. If we do not ensure that purge has
run to completion, the results on 10.3 and later could be
nondeterministic.

* Ensure no background purge is done;
* Better result showing actual number in case of failure;
* Higher and more safe difference threshold.

This causes failures in versioning.update-big in 10.3 and above

Problem was that wsrep thread argument was deleted on wrong
place. Furthermore, scan method incorrectly used unsafe c_ptr().
Finally, fixed wsrep thread initialization to correctly set
up thread_id and pass correct argument to functions and
fix signess problem causing compiler errors.

main.selectivity_innodb: Re-record the result.

MDEV-18863: Make wsrep_sst_mariabackup use Bash due to the += syntax.

For MDEV-15955, the fix in create_tmp_field_from_item() would cause a
compilation error. After a discussion with Alexander Barkov, the fix
was omitted and only the test case was kept.

In 10.3 and later, MDEV-15955 is fixed properly by overriding
create_tmp_field() in Item_func_user_var.

The execution of mtr in the Windows environment fails due to
the fact that the new code from MDEV-18565 does not take into
account the need to add the ".exe" extension to the names of
executable files when searching for pre-requisites that are
needed to run SST scripts (especially when using mariabackup)
and when searching paths to some other Galera utilities.
This patch fixes this flaw.

Also adding paths to the PATH environment variable is now
done with the correct delimiter character.

The execution of mtr in the Windows environment fails due to
the fact that the new code from MDEV-18565 does not take into
account the need to add the ".exe" extension to the names of
executable files when searching for pre-requisites that are
needed to run SST scripts (especially when using mariabackup)
and when searching paths to some other Galera utilities.
This patch fixes this flaw.

Also adding paths to the PATH environment variable is now
done with the correct delimiter character.

The execution of mtr in the Windows environment fails due to
the fact that the new code from MDEV-18565 does not take into
account the need to add the ".exe" extension to the names of
executable files when searching for pre-requisites that are
needed to run SST scripts (especially when using mariabackup)
and when searching paths to some other Galera utilities.
This patch fixes this flaw.

Also adding paths to the PATH environment variable is now
done with the correct delimiter character.

Some users and some scripts (for example, mysqld_multi.sh) use special
option groups with names like [mysqld1], [mysqld2], ..., [mysqldN].

But SST scripts can't currently fully support these option groups.
The only option group-related value it gets from the server is
--defaults-group-suffix, if that option was set for mysqld when
the server was started.

However, the SST scripts does not get told by the server to read
these option groups, so this means that the SST script will fail
to read options like innodb-data-home-dir when it is in a option
group like [mysqld1]...[mysqldN].

Moreover, SST scripts ignore many parameters that can be passed
to them explicitly and cannot transfer them further, for example,
to the input of mariabackup utility. Ideally, we want to transfer
all the parameters of the original mysqld call to utilities such
as mariabackup, however the SST script does not receive these
parameters from the server and therefore cannot transfer them to
mariabackup.

To correct these shortcomings, we need to transfer to the scripts
all of the parameters of the original mysqld call, and in the SST
scripts themselves provide for the transfer all of these parameters
to utilities such as mariabackup. To prevent these parameters from
mixing with the script's own parameters, they should be transferred
to SST script after the special option "--mysqld-args", followed by
the string argument with the original parameters, as it received by
the mysqld call at the time of launch (further all these parameters
will be passed to mariabackup, for example).

In addition, the SST scripts themselves must be refined so that
they can read the parameters from the user-selected group, not just
from the global mysqld configuration group. And also so that they
can receive the parameters (which important for their work) as
command-line arguments.

Some users and some scripts (for example, mysqld_multi.sh) use special
option groups with names like [mysqld1], [mysqld2], ..., [mysqldN].

But SST scripts can't currently fully support these option groups.
The only option group-related value it gets from the server is
--defaults-group-suffix, if that option was set for mysqld when
the server was started.

However, the SST scripts does not get told by the server to read
these option groups, so this means that the SST script will fail
to read options like innodb-data-home-dir when it is in a option
group like [mysqld1]...[mysqldN].

Moreover, SST scripts ignore many parameters that can be passed
to them explicitly and cannot transfer them further, for example,
to the input of mariabackup utility. Ideally, we want to transfer
all the parameters of the original mysqld call to utilities such
as mariabackup, however the SST script does not receive these
parameters from the server and therefore cannot transfer them to
mariabackup.

To correct these shortcomings, we need to transfer to the scripts
all of the parameters of the original mysqld call, and in the SST
scripts themselves provide for the transfer all of these parameters
to utilities such as mariabackup. To prevent these parameters from
mixing with the script's own parameters, they should be transferred
to SST script after the special option "--mysqld-args", followed by
the string argument with the original parameters, as it received by
the mysqld call at the time of launch (further all these parameters
will be passed to mariabackup, for example).

In addition, the SST scripts themselves must be refined so that
they can read the parameters from the user-selected group, not just
from the global mysqld configuration group. And also so that they
can receive the parameters (which important for their work) as
command-line arguments.