Fix a race condition in the testcase. The testcase assumed that
State='Sending data' means that the thread is already in an
InnoDB lock wait. This is not case, there is a gap between the
state changing to Sending data and execution reaching the point
where it is waiting for a lock.

Use a more precise check instead, through I_S.INNODB_TRX.

The problem was caused by the following scenario:

Subquery's table has two indexes, KEY a(a), KEY a_b(a,b)

- LATERAL DERIVED optimization decides to use index a.
  = The subquery uses ref access over key a.
- test_if_skip_sort_order() sees that KEY a_b satisfies the
  subquery's GROUP BY clause, and attempts to switch to it.
  = It fails to do so, because KEYUSE objects for index a_b
    are switched off.

Fixed by disallowing to change the ref access key if it uses KEYUSE
objects injected by LATERAL DERIVED optimization.

Problem:
========
180511 11:07:58 [ERROR] Slave I/O: Unexpected master's heartbeat data:
heartbeat is not compatible with local info;the event's data: log_file_name
mysql-bin.000009 log_pos 1054262041, Error_code: 1623

Analysis:
=========
In replication setup when master server doesn't have any events to send to
slave server it sends an 'Heartbeat_log_event'. This event carries the
current binary log filename and offset details. The offset values is stored
within 4 bytes of event header. When the size of binary log is higher than
UINT32_MAX the log_pos values will not fit in 4 bytes memory.  It overflows
and hence slave stops with an error.

Fix:
===
Since we cannot extend the common_header of Log_event class, a greater than
4GB value of Log_event::log_pos is made to be transported with a HeartBeat
event's sub-header.  Log_event::log_pos in such case is set to zero to
indicate that the 8 byte sub-header is allocated in the event.

In case of cross version replication following behaviour is expected

OLD - Server without fix
NEW - Server with fix

OLD<->NEW : works bidirectionally as long as the binlog offset is
            (normally) within 4GB.

When log_pos > UINT32_MAX
OLD->NEW  : The 'log_pos' is bound to overflow and NEW slave may report
            an invalid event/incompatible heart beat event error.
NEW->OLD  : Since patched server sets log_pos=0 on overflow, OLD slave will
            report invalid event error.

- Fixing post-push failure of innodb_fts_misc_1 test case.

InnoDB tries to fetch the deleted doc ids for discarded
tablespace. In i_s_fts_deleted_generic_fill(), InnoDB needs
to check whether the table is discarded or not before fetching
deleted doc ids.

fil_ibd_load(): Remove a message that is basically saying that
everything works as expected. The other "Ignoring data file" message
about the presence of an extraneous file will be retained
(and expected by the test innodb.log_file_name).

This reverts commit 8880dff2.

This commits replaces the call of the function setup_tables() with
a call of the function setup_tables_and_check_access() in the method
Multiupdate_prelocking_strategy::handle_end().
There is no known bug that would require this change. However the change
aligns this piece of code with the code existed before the patch for
MDEV-24823.

MDEV-25501 routine_definition in information_schema.routines loses tablename if it starts with an _ and is not backticked

remove code duplication in Lex_input_stream::scan_ident_middle(),
make sure identifiers are always use the same code path whether
they start form an underscore or not.

Attempt to build MariaDB server on MacOS could result in
compilation errors like the following one:

  In file included from server-10.2/storage/perfschema/cursor_by_account.cc:28:
  In file included from server-10.2/include/my_global.h:287:
  In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/include/c++/v1/math.h:309:
  In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/include/c++/v1/type_traits:418:
    server-10.2/version:1:1: error: expected unqualified-id

    MYSQL_VERSION_MAJOR=10
    ^
  server-10.2/build.dir/include/my_config.h:529:29: note: expanded from macro 'MYSQL_VERSION_MAJOR'

This kind of compiler errors occur by the reson that compiler's system headers
contain the directive '#include <version>' and a compiler is invoked
with -I${CMAKE_SOURCE_DIR}.

The MariaDB source code root directory contains the file VERSION that is handled
by the compiler during processing the directive #include <version>
since file names on MacOS are case insensetive, so version and VERSION is treated as
the same file name.

To fix the issue the source code root directory should be removed from a list
of directories used by the compiler for include search path.

The problem is that sharing default expression among set instruction
leads to attempt access result field of function created in
other instruction runtime MEM_ROOT and already freed
(a bit different then MySQL problem).

Fix is the same as in MySQL (but no optimisation for constant), turn
DECLARE a, b, c type DEFAULT expr;
to
DECLARE a type DEFAULT expr, b type DEFAULT a, c type DEFAULT a;

Removed explicit InnoDB monitor startup and used just functions
to print current lock information.

Problem was that we should skip strict password validation on
applier nodes similarly as is done for slave nodes.

Replace unnecessary sleeps with real wait_conditions to make
sure correct cluster sizes.

don't try to lowercase a db name if it's zero-length.
(empty_lex_str is not writable, even db.str[0]=0 will fail)

Relax the assert condition. A locked table that did existed prior to
CREATE IF NOT EXIST, retains the MDL_NO_SHARED_READ_WRITE MDL lock prio.

plugin variables in SET  only locked the plugin till the end of the
statement. If SET with a plugin variable was prepared, it was possible
to uninstall the plugin before EXECUTE. Then EXECUTE would crash,
trying to resolve a now-invalid pointer to a disappeared variable.

Fix: keep plugins locked until the prepared statement is closed.

encourage the use of mysql_secure_installation,
that can always set the root password correctly for all root accounts,
no matter how many are there and what the structure of privilege tables is

InnoDB startup hangs if a DDL transaction needs to be
rolled back and a recovered transaction on statistics
tables exists. In that case, InnoDB should rollback
the transaction which holds locks on innodb_table_stats
or innodb_index_stats during trx_rollback_or_clean_recovered().

InnoDB fails to fetch the index type when innodb dictionary
doesn't match with frm. InnoDB should return corrupted if it
can't find the index in ha_innobase::index_type().

table->move_fields wasn't undone in case of error.

1. move_fields is unconditionally undone even when error is occurred
2. cherry-pick an assertion in `ptr_in_record`, which is already in 10.5

The assertion is improved: storage engines like myisam always have to store
at least one field, so the assertion does not cover tables with no stored
columns.

So we are having a race condition of three of threads, resulting in a
deadlock backoff in purge, which is unexpected.

More precisely, the following happens:
T1: NOCOPY ALTER TABLE begins, and eventually it holds MDL_SHARED_NO_WRITE
 lock;
T2: FLUSH TABLES begins. it sets share->tdc->flushed = true
T3: purge on a record with virtual column begins. it is going to open a
 table. MDL_SHARED_READ lock is acquired therefore.
Since share->tdc->flushed is set, it waits for a TDC purge end.
T1: is going to elevate MDL LOCK to exclusive and therefore has to set
 other waiters to back off.
T3: receives VICTIM status, reports a DEADLOCK, sets OT_BACKOFF_AND_RETRY
 to Open_table_context::m_action

My fix is to allow opening table in purge while flushing. It is already
done the same way in other maintainance facilities like REPAIR TABLE.

Another way would be making an actual backoff, but Open_table_context
does not allow to distinguish it from other failure types, which still
seem to be unexpected. Making this would require hacking into
Open_table_context interface for no benefit, in comparison to passing
MYSQL_OPEN_IGNORE_FLUSH during table open.

innodb_debug_sync was introduced in commit
b393e2cb and reverted in
commit fc58c172 due to memory leak reported
by valgrind, see MDEV-21336.

The leak is now fixed by adding `rw_lock_free(&slot->debug_sync_lock)`
after background thread working loop is finished, and the patch is
reapplied, with respect to c++98 fixes by Marko.

The missing DEBUG_SYNC for MDEV-18546 in row0vers.cc is also reapplied.

Remove plugin functions via item_create_remove() at deinit time.

Item_func_history (is_history()) is a bool function that checks if the
row is the history row by checking row_end->is_max(). The argument to
this function must be row_end system field.

Added the above function to conjunction with SYSTEM_TIME_BEFORE
versioning condition.

row_merge_is_index_usable(): Allow access to any SEQUENCE, even if it was
created after the read view. SQL sequences are no-rollback tables with no
history at all.