rtr_pcur_getnext_from_path(): Remove a bogus condition.
The predicate lock should be acquired also on no match,
to ensure that the locking read will be repeatable.

This is based on the following fix in MySQL 5.7.24:

commit 365111c590082984dbae42e1d1da28ac3f7fb5bd
Author: Jimmy Yang <jimmy.yang@oracle.com>
Date:   Wed Jun 6 16:23:00 2018 -0700

    Fix Bug 27577612 - CONCURRENT SERIALIZABLE TRANSACTIONS CAN INSERT INTO
    AN AREA SELECTED FOR UPDATE
    Backport fix to mysql-5.7
Reviewed-by: Allen Lai <allen.lai@oracle.com>

No test case is added, because the MySQL 5.7 test case would pass
even when the fix is not present. We would need a test case that
only causes a locking conflict on the spatial index.

row_ins_check_foreign_constraint(): Do not overwrite hard errors
with the soft error DB_LOCK_WAIT. This prevents an infinite
wait loop when DB_INTERRUPTED was returned. For DB_LOCK_WAIT,
row_insert_for_mysql() would keep invoking row_ins_step() and the
transaction would remain active until the server shutdown is initiated.

This reverts commit 2d4075e1
where the debug assertion was added. There seems to be a potential
problem in the purge of indexes that depend on virtual columns.

Ultimately, we should change the InnoDB undo log format so that
all actual secondary index keys are stored there, also for
virtual or spatial indexes. In that way, purge and rollback would
be more straightforward.

On Windows, a mismatch between TIMETPF ("%ld") and time_t would be reported.
Use "%ld" and long, like the code used to be.

The setting innodb_safe_truncate=ON reduces compatibility with older
versions of MariaDB and backup tools in two ways.

First, we will be writing TRX_UNDO_RENAME_TABLE records, which older
versions do not know about. These records could be misinterpreted if
a DDL transaction was recovered and would be rolled back.
Such rollback is only possible if the server was killed while
an incomplete DDL transaction was persisted. On transaction completion,
the insert_undo log pages would only be repurposed for new undo log
allocations, and their contents would not matter. So, older versions
will not have a problem with innodb_safe_truncate=ON if the server was
shut down cleanly.

Second, to prevent such recovery failure, innodb_safe_truncate=ON will
cause a modification of the redo log format identifier, which will
prevent older versions from starting up after a crash. MariaDB Server
versions older than 10.2.13 will refuse to start up altogether, even
after clean shutdown.

A server restart with innodb_safe_truncate=OFF will restore compatibility
with older server and backup versions.

Added only test case because the bug was fixed by the patch for mdev-16992.

Opened up MYSQL_TYPE _DATETIME{,2} <-> _NEWDATE conversions for replication.

row_build_index_entry_low(): Assert that when the value of a
virtual column is not available, this can only happen when
the index creation was completed but not committed yet.

This change is not fixing any bug, making a debug assertion
stricter, so that bugs can be caught in the future.

Ultimately, we should change the InnoDB undo log format so that
all actual secondary index keys are stored there, also for
virtual or spatial indexes. In that way, purge and rollback would
be more straightforward.

When we have a query which has implicit_grouping then we are sure that we would end up with only one
row so there is no point to do DISTINCT computation

The failure caused by MDEV-16387

           upon INSERT .. SELECT

The function Item *Item_direct_view_ref::derived_field_transformer_for_where()
erroneously did not strip off ref wrappers from references to materialized
derived tables / views. As a result the expressions that contained some
references of the type Item_direct_view_ref to columns of a materialized
derived table / view V were pushed into V incorrectly. This could cause
crashes for some INSERT ... SELECT statements.

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.

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.

Add wait on second node.

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

if thread specific memory is requested and current_thd is NULL.

Leave DBUG_ASSERT() in place, to check in DBUG version.

Make the testcase stable

The bug appears as a slave SQL thread hanging in
rpl_parallel_thread_pool::get_thread() while there are no slave worker
threads to awake it.

The reason of the hang is that at the parallel slave worker pool
activation the being stared SQL thread could read the worker pool size
concurrently with pool deactivation. At reading the SQL thread did not
employ necessary protection from a race.

Fixed with making the SQL thread at the pool activation first
to grab the same lock as potential deactivator also does prior
to access the pool size.

			table for purge thread

Problem:
=======
	Purge tries to fetch mdl lock for the whole table even though it tries
to open one of the partition. But table name length was wrongly set to indicate
the partition name too.

Solution:
========
- Table name length should identify the table name only not the partition name.

           derived table / view by equality

Now rows of a materialized derived table are always put into a
temporary table before join operation. If BNLH is used to join this
table with the result of a partial join then both operands of the
join are actually put into main memory. In most cases this is not
efficient.
We could avoid this by sending the rows of the derived table directly
to the join operation. However this kind of data flow is not supported
yet.
Fixed by not allowing usage of hash join algorithm to join a materialized
derived table if it's joined by an equality predicate of the form
f=e where f is a field of the derived table.

           derived table / view by equality

Now rows of a materialized derived table are always put into a
temporary table before join operation. If BNLH is used to join this
table with the result of a partial join then both operands of the
join are actually put into main memory. In most cases this is not
efficient.
We could avoid this by sending the rows of the derived table directly
to the join operation. However this kind of data flow is not supported
yet.
Fixed by not allowing usage of hash join algorithm to join a materialized
derived table if it's joined by an equality predicate of the form
f=e where f is a field of the derived table.

Amend previous patch, so it works in all cases (also for "change user"
command, and for RESET CONNECTION in 10.3)

MDEV-17313 Data race in ib_counter_t

This warning come from a copy() operation of type:
memcpy(ptr, ptr+A, B), which is safe but produces a warning
when run with valgrind.

To avoid the warning, I added copy_or_move() method which uses
memmove() instead of memcpy().

In 10.3 the change in item_strfunc::Item_func_concat() has to be mirroed
in Item_func_concat_oracle() to avoid future valgrind warnings.

This is a regression caused by
commit 73af8af0
(MDEV-15325 Incomplete validation of missing tablespace during recovery).

If the recv_sys->addr_hash hash table ran out of memory, we would
have to do crash recovery in multiple passes. If some tablespaces were
missing, after the MDEV-15325 fix we would rescan the remaining redo log.
But, we could incorrectly reset the "rescan" flag. Because of this, we
would fail to apply some of the oldest redo log records to the data files.
(The recv_sys->addr_hash would only contain records from the latest
redo log scan batch.)

Fix:

After checking for missing tablespaces, reset the flag rescan=true,
so that all redo log records will be re-read and applied.