Make SEL_ARG graph traversal code in sel_arg_range_seq_next() set
max_key_parts first.

(Pushing to 10.4 first)

accessing it.

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).

* 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()

Make the skip_key a bit faster.

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.

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

A syntax error in the mysqld_multi.sh script has been fixed
here + a "--defaults-group-suffix" option has been moved to
the top of the mysqld options list.

Thanks to Eugene Kosov for noting that the fix is incomplete.
It turns out that on instant DROP/reorder column (MDEV-15562),
we must always write the metadata record, even though the table
was empty. Alternatively, we should guarantee that all undo
log records for the table have been purged. (Attempting to do
that by updating table_id leads to other problems; see
commit 1b31d885.)

It would be tempting to remove dict_index_t::clear_instant_alter()
altogether, but it turns that we need that when the instant ALTER TABLE
operation of a first-time DROP COLUMN is being rolled back.

innobase_instant_try(): Clarify a comment. Purge never calls
dict_index_t::clear_instant_alter(), but it may invoke
dict_index_t::clear_instant_add(). On first-time instant DROP/reorder,
always write a metadata record, even if the table is empty.

The test encryption.innodb-redo-badkey was accidentally disabled
until commit 23657a21 enabled
it recently. Once it was enabled, it started failing randomly.

recv_recover_corrupt_page(): Do not assume that any redo log exists
for the page. A page may be unnecessarily read by read-ahead.
When noting the corruption, reset recv_addr->state to RECV_PROCESSED,
so that even if the same page is re-read again, we will only
decrement recv_sys->n_addrs once.

Spotted by Thirunarayanan Balathandayuthapani.

rw_lock_own(), rw_lock_own_flagged(): Traverse the rw_lock_t::debug_list
only after quickly checking if the thread is holding X-latch or SX-latch.

chkconfig --add and --del [might] invoke /sbin/insserv
and even if chkconfig exists, insserv might not (SLES15).

Ignore chkconfig --del errors - it's a "best effort" cleanup anyway

The test innodb_fts.fulltext_table_evict was only creating 1000 tables
with fulltext indexes, only to check that no tables with fulltext
indexes are being evicted.

The reason why tables containing fulltext indexes cannot be evicted is
that fts_optimize_init() invokes dict_table_prevent_eviction().

For CMAKE_BUILD_TYPE=Debug, the default MYSQL_MAINTAINER_MODE=AUTO
implies -Werror along with other flags in cmake/maintainer.cmake,
which would break the debug builds when CMAKE_CXX_FLAGS include -O2.

This fix includes a backport of 6dd3f240
from MariaDB 10.3.

The crash scenario is as follows:

(1) A non-empty table exists.
(2) MDEV-15562 instant ADD/DROP/reorder has been invoked.
(3) Some purgeable undo log exists for the table.
(4) The table becomes empty, containing not even any delete-marked records,
only containing the hidden metadata record that was added in (2).
(5) An instant ADD/DROP/reorder column is executed, and the table
is emptied and the (2) metadata removed.
(6) Purge processes an undo log record from (3), which will refer to
a non-existent clustered index field, because the metadata that
was created in (2) was remoeved in (5).

We fix this by adjusting step (5) so that we will never remove the
MDEV-15562-style metadata record. Removing the MDEV-11369 metadata
record (instant ADD COLUMN to the end of the table) is completely
fine at any time when the table becomes empty, because
dict_index_t::n_fields will remain unchanged.

innobase_instant_try(): Never remove the MDEV-15562 metadata record.

page_cur_delete_rec(): Do not reset FIL_PAGE_TYPE when the
MDEV-15562 metadata record is being removed as part of
btr_cur_pessimistic_update() invoked by innobase_instant_try().

Always initialize ScopedStatementReplication::saved_binlog_format,
so that GCC cannot emit a bogus warning about
ScopedStatementReplication::~ScopedStatementReplication() using the
variable.

The code was originally introduced in
commit d998da03.

lock_print_info::operator(): Do not dereference purge_sys.query in case
it is NULL. We would not initialize purge_sys if innodb_force_recovery
is set to 5 or 6.

The test case will be added by merge from 10.2.

Test innodb_read_only startup (which will be refused after a crash),
and test also innodb_force_recovery=5, and extract some change buffer
merge statistics. Omit any statistics about delete (purge) buffering,
because purge could happen at any time.

Use the sequence storage engine for populating the table.

Add a test case. MariaDB Server 10.2 is not affected.

A syntax error in the mysqld_multi.sh script has been fixed
here + a "--defaults-group-suffix" option has been moved to
the top of the mysqld options list.

In MariaDB 10.4.0, commit 09af00cb
removed the crash-upgrade logic for the MariaDB 10.2
innodb_safe_truncate=OFF TRUNCATE TABLE (which was the only option
between MariaDB 10.2.2 and 10.2.18), but failed to adjust some
comments and code.

buf_page_io_complete(): Remove a bogus comment about TRUNCATE.

dict_recreate_index_tree(): Unused function; remove.

fil_space_t::stop_new_ops: Clarify the comment.

fil_space_acquire_low(): Remove a bogus comment about TRUNCATE.

fil_check_pending_ops(), fil_check_pending_io(): Adjust a warning message.
This code is only invoked as part of DISCARD TABLESPACE or DROP TABLE.
DROP TABLE is internally used as part of ALTER TABLE, OPTIMIZE TABLE,
or TRUNCATE TABLE.

RemoteDatafile::create_link_file(): Clarify a comment.

ibuf_delete_for_discarded_space(): Clarify the function comment.

dict_table_x_lock_indexes(), dict_table_x_unlock_indexes():
Merge with the only remaining caller, row_quiesce_set_state().

page_create_zip(): Remove a bogus comment about TRUNCATE.