Additional changes:

1. Adding a fast path for ASCII characters
2. Adding dedicated MY_COLLATION_HANDLERs for collations with no contractions
   (for utf8 and for utf8mb4 character sets). The choice between
   the full-featured handler and the "no contraction" handler is
   made at the collation initialization time.

row_ins_clust_index_entry_low(): Do not call dtuple_t::trim()
before row_ins_clust_index_entry_by_modify(), so that the values
of all columns will be available in row_upd_build_difference_binary().
If applicable, the tuple can be trimmed in btr_cur_optimistic_update()
or btr_cur_pessimistic_update(), which will be called by
row_ins_clust_index_entry_by_modify().

Added only test case because the bug was fixed by the patch for mdev-17382.

The function and_new_conditions_to_optimized_cond() incorrectly handled
the WHERE conditions with one multiple equality and one IN subquery predicate
that could be converted into a jtbm semi-join. This could cause crashes.

The fix code was prepared by Galina Shalygina.

try fix OSX build

The syntax error happened because we had not implemented a different print for
percentile functions. The syntax is a bit different when we use percentile functions
as window functions in comparision to normal window functions.
Implemented a seperate print function for percentile functions

           in Field_iterator_table::create_item

When IN predicate is converted to IN subquery we have to ensure that
any item from the select list of the subquery has some name and this name
is unique across the select list.
This was not guaranteed by the code before the patch for MDEV-17222.
If the name of an item of the select list was not set, and this happened
for binary constants, then the server crashed. If the first row in the IN
list contained the same constant in two different positions then the server
returned an error message.
This was fixed by providing all constants in the first row of the IN list
with generated names.

disable rpl_mdev382 on Windows, due to unix shell escaping used there.

Bump mysqldump to a version greater than that on the 10.3 branch.

A prepared backup from Mariabackup does not really need to contain any
redo log file, because all log will have been applied to the data files.

When the user copies a prepared backup to a data directory (overwriting
existing files), it could happen that the data directory already contained
redo log files from the past. mariabackup --copy-back) would delete the
old redo log files, but a user’s own copying script might not do that.
To prevent corruption caused by mixing an old redo log file with data
files from a backup, starting with MDEV-13311, Mariabackup would create
a zero-length ib_logfile0 that would prevent startup.

Actually, there is no need to prevent InnoDB from starting up when a
single zero-length file ib_logfile0 is present. Only if there exist
multiple data files of different lengths, then we should refuse to
start up due to inconsistency. A single zero-length ib_logfile0 should
be treated as if the log files were missing: create new log files
according to the configuration.

open_log_file(): Remove. There is no need to open the log files
at this point, because os_file_get_status() already determined
the size of the file.

innobase_start_or_create_for_mysql(): Move the creation of new
log files a little later, not when finding out that the first log
file does not exist, but after finding out that it does not exist
or it exists as a zero-length file.

Rename the 10.2-specific configuration option innodb_unsafe_truncate
to innodb_safe_truncate, and invert its value.

The default (for now) is innodb_safe_truncate=OFF, to avoid
disrupting users with an undo and redo log format change within
a Generally Available (GA) release series.

ib_counter_t: make all reads/writes to m_counter relaxed atomical

We keep the MySQL 5.7 backup-incompatible TRUNCATE TABLE
only in MariaDB Server 10.2. In 10.3 and later releases,
only the backup-friendly TRUNCATE will be available.

While MariaDB Server 10.2 is not really guaranteed to be compatible
with Percona XtraBackup 2.4 (for example, the MySQL 5.7 undo log format
change that could be present in XtraBackup, but was reverted from
MariaDB in MDEV-12289), we do not want to disrupt users who have
deployed xtrabackup and MariaDB Server 10.2 in their environments.

With this change, MariaDB 10.2 will continue to use the backup-unsafe
TRUNCATE TABLE code, so that neither the undo log nor the redo log
formats will change in an incompatible way.

Undo tablespace truncation will keep using the redo log only. Recovery
or backup with old code will fail to shrink the undo tablespace files,
but the contents will be recovered just fine.

In the MariaDB Server 10.2 series only, we introduce the configuration
parameter innodb_unsafe_truncate and make it ON by default. To allow
MariaDB Backup (mariabackup) to work properly with TRUNCATE TABLE
operations, use loose_innodb_unsafe_truncate=OFF.

MariaDB Server 10.3.10 and later releases will always use the
backup-safe TRUNCATE TABLE, and this parameter will not be
added there.

recv_recovery_rollback_active(): Skip row_mysql_drop_garbage_tables()
unless innodb_unsafe_truncate=OFF. It is too unsafe to drop orphan
tables if RENAME operations are not transactional within InnoDB.

LOG_HEADER_FORMAT_10_3: Replaces LOG_HEADER_FORMAT_CURRENT.

log_init(), log_group_file_header_flush(),
srv_prepare_to_delete_redo_log_files(),
innobase_start_or_create_for_mysql(): Choose the redo log format
and subformat based on the value of innodb_unsafe_truncate.

The test needs to be run with rocksdb_flush_log_at_trx_commit=1, otherwise
the changes do not survive a crash.

On the rollback of changes to SYS_COLUMNS, MDEV-15562 will
break the assumption that the only instantaneous changes to columns
are the addition to the end of the column list.

The function dict_table_t::rollback_instant(unsigned n)
is inherently incompatible with instantly dropping or reordering
columns.

When a change to SYS_COLUMNS is rolled back, we must simply evict
the affected table definition, at the end of the rollback. We cannot
free the table object immediately, because the current transaction
that is being rolled back may be holding a lock on the table and
its metadata record.

dict_table_remove_from_cache_low(): Replaced
by dict_table_remove_from_cache().

dict_table_remove_from_cache(): Add a third parameter keep=false,
so that the table can be freed by the caller.

trx_lock_t::evicted_tables: List of tables on which trx_t::evict_table()
was invoked.

trx_t::evict_table(): Evict a table definition during rollback.

trx_commit_in_memory(): Empty the trx->lock.evicted_tables list
after the locks were released, by freeing the table objects.

row_undo_ins_remove_clust_rec(), row_undo_mod_clust_low():
Invoke trx_t::evict_table() on the affected table if a change to
SYS_COLUMNS is being rolled back.

The error handling for ALTER TABLE…ALGORITHM=COPY as well as
CREATE TABLE used to commit the CREATE TABLE transaction and then
issue DROP TABLE in a separate transaction. This is unnecessarily
breaking atomicity during DDL operations. Let us revise it so
that the DROP TABLE will be executed within the same transaction,
which will finally be rolled back.

FIXME: Introduce an undo log record so that the data file would be
deleted on rollback and no DROP TABLE would be needed at all.

FIXME: Avoid unnecessary access to per-table tablespace during DROP TABLE.
If the .ibd file is going to be deleted anyway, we should not bother
to mark the pages free.

dict_create_add_foreigns_to_dictionary(): Do not commit the transaction.
We want simple rollback in case dict_load_foreigns() would fail.

create_table_info_t::create_table(), row_create_index_for_mysql(),
row_table_add_foreign_constraints(): Before invoking rollback, drop
the table. Rollback would invoke trx_t::evict_table(), and after that
dropping the table would be a no-op.

ha_innobase::create(): Before rollback, drop the table. If the SQL
layer invoked ha_innobase::delete_table() later, it would be a no-op
because the rollback would have invoked trx_t::evict_table().

dict_index_t::first_user_field(): Return the first data field in
a clustered index, that is, the field after the PRIMARY KEY and
the two system columns DB_TRX_ID, DB_ROLL_PTR.

dtuple_convert_big_rec(): Remove some local variables.

Add wait on second node.

Ensure that no redo log checkpoint occurs in a critical section
of a recovery test.