There is several different ways to incorrectly define
foreign key constraint. In many cases earlier MariaDB
versions the error messages produced by these cases
are not very clear and helpful. This patch improves
the warning messages produced by foreign key parsing.

Added better error message that will be printed when foreign key
constraint name in create table is not unique in database.

GET_LOCK() silently accepted negative values and NULL for timeout.
Fixed GET_LOCK() to issue a warning and return NULL in such cases.

Fixed memory loss detected on P8. This can happen when we call after_flush but never call after_rollback() or after_commit().

The old code used pthread_setspecific() to store temporary data used by the thread.
This is not safe when used with thread pool, as the thread may change for the transaction.

The fix is to save the data in THD, which is guaranteed to be properly freed.
I also fixed the code so that we don't do a malloc() for every transaction.

field.cc
- Fixed warning about overlapping memory copy (backport from 10.0)

Item_subselect.cc
- Fixed core dump in main.view
- Problem was that thd->lex->current_select->master_unit()->item was not set, which caused crash in maxr_as_dependent

sql/mysqld.cc
- Got error on shutdown as we where freeing mutex before all THD objects was freed
  (~THD uses some mutex). Fixed by during shutdown freeing THD inside mutex.

sql/log.cc
- log_space_lock and LOCK_log where locked in inconsistenly. Fixed by not having a log_space_lock around purge_logs.

sql/slave.cc
- Remove unnecessary log_space_lock
- Move cond_broadcast inside lock to ensure we don't miss the signal

Analysis: At check_trx_exists function InnoDB allocates
a new trx if no trx is found from thd but this newly
allocated trx is not registered to thd. This is unsafe,
because nothing prevents InnoDB plugin from being uninstalled
while there's active transaction. This can cause crashes, hang
and any other odd behavior. It may also corrupt stack, as
functions pointers are not available after dlclose.

Fix: The fix is to use thd_set_ha_data() when
manipulating per-connection handler data. It does appropriate
plugin locking.

The fix is that if the slave has a different integer size than
the master, then they will assume the master has the same signed/unsigned modifier
as the slave.

This means that one can safely change a coon the slave an int to a bigint
or an unsigned int to an unsigned int.  Changing an unsigned int to an
signed bigint will cause replication failures when the high bit of the
unsigned int is set.

We can't give an error if the signess is different on the master and slave
as the binary log doesn't contain the signess of the column on the master.

The fix is that if the slave has a different integer size than
the master, then they will assume the master has the same signed/unsigned modifier
as the slave.

This means that one can safely change a coon the slave an int to a bigint
or an unsigned int to an unsigned int.  Changing an unsigned int to an
signed bigint will cause replication failures when the high bit of the
unsigned int is set.

We can't give an error if the signess is different on the master and slave
as the binary log doesn't contain the signess of the column on the master.

Fix for MDEV-8301;  Statistics for a thread could be counted twice in SHOW STATUS while thread was ending

Fixed by adding a marker if we have added the thread statistics to the global counters.

- Removing use of calls to current_thd
- More DBUG_PRINT
- Code style changes
- Made some local functions static
Ensure that calls to print_keyuse are locked with mutex to get all lines in same debug packet

SELECT ... WHERE XX IN (SELECT YY)
this was transformed to something like:
SELECT ... WHERE IF_EXISTS(SELECT ... HAVING XX=YY)

The bug was that for normal execution XX was fixed in the original outer SELECT context while in PS it was fixed in the sub query context and this confused the optimizer.

Fixed by ensuring that XX is always fixed in the outer context.

Fixed crashing bug when using ONLY_FULL_GROUP_BY in a stored procedure/trigger that is repeatedly executed.
This is MDEV-7601, including it's sub tasks MDEV-7594, MDEV-7555, MDEV-7590, MDEV-7581, MDEV-7589

The problem was that select_lex->non_agg_fields was not properly reset for re-execution and this caused an overwrite of a random memory position.
The fix was move non_agg_fields from select_lext to JOIN, which is properly reset.

* take into account that example may be NULL
* use example->safe_charset_converter(), copy-paste from
  Item::safe_charset_converter() (example might have its own
  implementation)
* handle the case when the charset doesn't need conversion
  (and return this).

* add a test when server certificate is verified successfully
* one test with two combinations (instead of two tests)
* verbose tets: make it print what it is doing
* fix the test to work with yassl and no-ssl builds

            keys

Fixed that OPTIMIZE TABLE against MyISAM/Aria table may write uninitialized key
root position for disabled keys.

           semisync plugin and setting rpl_semi_sync_master_enabled

There was race condition between INSTALL PLUGIN and SET. It was caused by a
gap in INSTALL PLUGIN when plugin variables were registered but not fully
initialized. Accessing such variables concurrently may reference uninitialized
memory, specifically sys_var_pluginvar::plugin.

Fixed by initializing sys_var_pluginvar::plugin early, before variable is
registered.

           semisync plugin and setting rpl_semi_sync_master_enabled

Cleanup:
Removed my_intern_plugin_lock() and my_intern_plugin_lock_ci() wrappers. They
were obsoleted by revision f56dd32b.

instead of running them only when ssl is not compiled in

"Range Checked for Each Record" should be only employed when the other
option would be cross-product join (i.e. the other option is so bad that
we hardly risk anything).

Previous logic was: use RCfER if there are no possible quick selects, or
quick select would read > 100 rows. Also, it didn't always work as
expected due to range optimizer changing table->quick_keys and us
looking at sel->quick_keys.

Another angle is that recent versions have enabled use of Join Buffering
in e.g. outer joins. This further reduces the range of cases where RCfER
should be used.

We are still unable to estimate the cost of RCfER with any precision, so
now changing the condition of "no quick select or quick->records> 100"
to a hopefully better condition "no quick select or quick would cost more
than full table scan".

Using --ssl-verify-server-cert and --ssl[-*] implies that
the ssl connection is required. The mysql client will now print an error if ssl
is required, but the server can not handle a ssl connection.

MDEV-7695 MariaDB - ssl - fips: can not connect with --ssl-cipher=DHE-RSA-AES256-SHA - handshake failure

Change 512bit DH key to 1024bit to meet FIPS requirements

Changing the error message to:
 "...from type 'decimal(0,?)/*old*/' to type ' 'decimal(10,7)'..."
So it's now clear that the master data type is OLD decimal.

Removing Item_cache::used_table_map, Item_cache::used_tables() and
Item_cache::set_used_tables(). Using the same inherited from
Item_basic_constant implementations instead.

remove/replace deprecated options

   More fixes to assure the order of queries in the log.

  This test also should be fixed - delay added so the connection
  event doesn't happen before the query.

   Connection event can happen before the query ends. Added a delay to
   confirm the order.

  Fhe GEOMETRY field should be handled just as the BLOB field. So that was fiexed in field_conv.
  One additional bug was found and fixed meanwhile - thet the geometry field subtypes
  should also be merged for UNION command.

  The MYSQL_AUDIT_NOTIFY_CONNECTION_CONNECT() call moved to the login_connection()
  function. So that it'll be invoked in any thread handling mode.

        If the SET PASSWORD query doesn't have the password string,
        the parsing of it can fail. It manifested first in MySQL 5.6 as
        it started to hide password lines sent to the plugins.
        Fixed by checking for that case.

   Symbols like TAB or NEWLINE should be escaped, which was
        forgotten in one place.

Check that leaf table list is really built before storing it.