LEX::parsed_select_expr_cont(): Replace a condition with an
assertion DBUG_ASSERT(!s2->next_select()), and always
initialize sel1=s2, because all subsequent code paths will
assign to sel1->first_nested.

This was flagged by GCC reporting -Wmaybe-uninitialized
for the statement last->link_neighbour(sel1).

Moving geometry types aggregation inside Type_collection_geometry

This change introduces a static method Type_aggregator::find_handler_in_array(),
which will later be reused by other data type plugins.

If we have a mixture of:
- a MariaDB standard (built-in permanent) data type, and
- a non-standard (optionally compiled or pluggable) data type,
then ask the type collection of the non-standard type to aggregate the mixture.

If the non-standard collection fails, then continue aggregation
with Type_handler_data.

Adding error reporting (ER_UNKNOWN_DATA_TYPE) when a handler name read
from EXTRA2_FIELD_DATA_TYPE_INFO is not known to the server.

* MDEV-20225 BF aborting SP execution

When stored procedure execution was chosen as victim for a BF abort, the old implemnetationn called for rollback immediately
when execution was inside SP isntruction. Technically this happened in wsrep_after_statement() call, which identified the
need for a rollback.
The problem was that MariaDB does not accept rollback (nor commit) inside sub statement, there are several asserts about it,
checking for THD::in_sub_stmt.

This patch contains a fix, which skips calling wsrep_after_statement() for SP execution, which is marked as BF must abort. Instead,
we return error code to upper level, where rollback will eventually happen, ouside of SP execution.
Also, appending the affected trigger table (dropped or created) in the populated key set for the write set,
which prevents parallel applying of other transactions working on the same table.

* MDEV-20225 BF aborting SP execution, second patch

First PR missed 4 commits, which are now squashed in this patch:
- Added galera_sp_bf_abort test.
  A MTR test case which will reproduce BF-BF conflict if all keys
  corresponding to affected tables are not assigned for DROP TRIGGER.
- Fixed incorrect use of sync pointsin MDEV-20225
- Added condition for SQLCOM_DROP_TRIGGER in wsrep_can_run_in_toi()
  to make it replicate.

* MDEV-20225 BF aborting SP execution, third patch

The galera_trigger.test caused a situation, where SP invocation caused a trigger
to fire, and the trigger executed as sub statement SP, and was BF aborted by applier.
because of wsrep_after_statement() was called for the sub-statement level, it ended up
in exeuting rollback and asserted there.
Thus fix will catch sub-statement level SP execution, and avoids calling wsrep_after_statement()

Fixes -Winconsistent-missing-override in
MDEV-16144 Default TIMESTAMP clause for SELECT from versioned

Make the skip_key a bit faster.

vers_sys_type_t -> vers_kind_t

1. Removed TIMESTAMP/TRANSACTION unit auto-detection in favor of default TIMESTAMP.

Reasons:

1.1. rare practical use and doubtful advantage of such auto-detection;
1.2. it conflicts with MDEV-16226 (TRX_ID-based versioned tables performance improvement).

Needless check_unit membership removed.

2. SQL: versioning type handling refactoring

Vers_type_handler hierarchy stores versioning properties of type.

virtual Type_handler::vers() accesses specialization of
Vers_type_handler for specific type.

virtual Vers_type_handler::kind() returns versioning kind
(timestamp/trx_id).

Removed Type_handler::Vers_history_point_check_unit() in favor of
Type_handler::vers().

Renames:

require_timestamp() -> require_timestamp_error()
require_trx_id() -> require_trx_id_error()

EDIT by Alexander Barkov (@abarkov):

check_sys_fields() moved to Vers_type_handler::check_sys_fields()

First character of the key name is just skipped, so the escapement
wasn't handled properly.

For release builds, do not declare unused variables.

unpack_row(): Omit a debug-only variable from WSREP diagnostic message.

create_wsrep_THD(): Fix -Wmaybe-uninitialized for the PSI_thread_key.

MDEV-20645: Replication consistency is broken as workers miss the error notification from an earlier failed group.

Analysis:
========
In general if there are three groups.
1 - Inserts 32 which fails due to local entry '32' on slave.
2 - Inserts 33
3 - Inserts 34

Each group considers itself as a waiter and it waits for prior group 'waitee'.
This is done in 'register_wait_for_prior_event_group_commit'. If there is no
other parallel group being scheduled then no waitee will be there.

Let us assume 3 groups are being scheduled in parallel.

3-> waits for 2-> waits for->1

'1' upon completion it checks is there any registered subsequent waiter. If
so it wakes up the subsequent waiter with its execution status. This execution
status is stored in wakeup_error.

If '1' failed then it sends corresponding wakeup_error to 2. Then '2' aborts
and it propagates error to '3'.  So all further commits are aborted.  This
mechanism works only when all transactions reach a stage where they are
waiting for their prior commit to complete.

In case of optimistic following scenario occurs.

1,2,3 are scheduled in parallel.

3 - Reaches group_commit_code waits for 2 to complete.
1 - errors out sets stop_on_error_sub_id=1.

When a group execution results in error its corresponding sub_id is set to
'stop_on_error_sub_id'. Any new groups queued for execution will check if
their sub_id is > stop_on_error_sub_id.  If it is true their execution will be
skipped as prior group execution failed.  'skip_event_group=1' will be set.
Since the execution of SQL thread is about to stop we just skip execution of
all the following event groups.  We still do all the normal waiting and wakeup
processing between the event groups as a simple way to ensure that everything
is stopped and cleaned up correctly.

Upon error '1' transaction checks for registered waiters. Since no one is
there it simply goes away.

2 - Starts the execution. It checks do I have a waitee.

Since wait_commit_sub_id == entry->last_committed_sub_id no waitee is set.

Secondly: 'entry->stop_on_error_sub_id' is set by '1'st execution.  Now
'handle_parallel_thread' code checks if the current group 'sub_id' is greater
than the 'sub_id' set within 'stop_on_error_sub_id'.

Since the above is true 'skip_event_group=true' is set.  Simply call
'wait_for_prior_commit' to wakeup all waiters.  Group '2' didn't had any
waitee and its execution is skipped.  Hence its wakeup_error=0.It sends a
positive wakeup signal to '3'. Which commits. This results in a missed
transaction. i.e 33 is missed and 34 is committed.

Fix:
===
When a worker learns that an earlier transaction execution has failed, and it
should not proceed for further execution, it should mark its own execution
status as failed so that it alerts its followers to abort as well.

mark big_tables deprecated, the server can put temp tables on disk
as needed avoiding "table full" errors.

in case someone would really need to force a tmp table to be created
on disk from the start and for testing allow tmp_memory_table_size
to be set to 0.

fix tests to use that instead (and add a test that it actually
works).

make sure in-memory TREE size limit is never 0 (it's [ab]using
tmp_memory_table_size at the moment)

remove few sys_vars.*_basic tests

MDEV-20639 ASAN SEGV in get_prefix upon modifying base column type with existing indexed virtual column