MDEV-23805 simplified the treatment of empty tables during ALTER TABLE,
which could prevent the scenarios that were previously reported and
fixed as MDEV-16131 and MDEV-24730.

With the MDEV-23805 fix, the statement
SET DEBUG_SYNC = 'now WAIT_FOR copied';
could occasionally time out, depending on timing.
Apparently, there was a race condition where purge could resume
(and empty the table) before ALTER TABLE got the chance to execute.
We must prevent the purge of history from running before
ALTER TABLE has started executing.

- In ha_innobase::prepare_inplace_alter_table(), InnoDB should
check whether the table is empty. If the table is empty then
server should avoid downgrading the MDL after prepare phase.
It is more like instant alter, does change only in dicationary
and metadata.

- Changed few debug test case to make non-empty DDL table

Upon investigation, decided this to be a compiler bug
(happens with new compiler, on code that did not change for the last 15 years)

Fixed by de-optimizing single function remove_key(), using MSVC pragma

MDEV-26991: CURRENT_TEST: main.mysql_binary_zero_insert 'grep' is not recognized as an internal or external command, operable program or batch file.

Removed grep from mysqldump command stream and instead,
extend the search_file pattern to search for rows containing
binary zeros instead of any occurance of '00' in the input

If it is not enabled, build wsrep as static "stub" library from wsrep_dummy.cc
´

Allow static plugins to export symbols (on Unix)
wsrep_info relies on wsrep defined symbols (e.g  LOCK_wsrep_config_state)
exported from mysqld

Means, plugin will not be available in embedded, even if compiled-in

This reverts commit 1a3570de.

This reverts commit e45f7f48.

- Add unit test.

Code cleanup: Remove Json_writer::is_on_fmt_helper_call. We already
maintain this state in fmt_helper.

If it is not enabled, build wsrep as static "stub" library from wsrep_dummy.cc
´

Allow static plugins to export symbols (on Unix)
wsrep_info relies on wsrep defined symbols (e.g  LOCK_wsrep_config_state)
exported from mysqld

in test main.range_vs_index_merge one path requires named JSON object:
assert.c:0(.annobin_assert.c_end)[0x7fe9d2270a76]
sql/my_json_writer.cc:43(Json_writer::on_start_object())[0x555e284f048a]
sql/my_json_writer.cc:59(Json_writer::start_object())[0x555e284ee6e8]
sql/my_json_writer.h:377(Json_writer_object::Json_writer_object(THD*))[0x555e281dce11]
sql/opt_range.cc:5137(get_best_disjunct_quick(PARAM*, SEL_IMERGE*, double))[0x555e287c576b]
sql/opt_range.cc:5492(merge_same_index_scans(PARAM*, SEL_IMERGE*, TRP_INDEX_MERGE*, double))[0x555e287c6cf6]
sql/opt_range.cc:5287(get_best_disjunct_quick(PARAM*, SEL_IMERGE*, double))[0x555e287c607a]
sql/opt_range.cc:3000(SQL_SELECT::test_quick_select

another one requires unnamed JSON:
mariadbd: /home/name/server/sql/my_json_writer.cc:379: bool Single_line_formatting_helper::on_add_member(const char*, size_t): Assertion `state== INACTIVE || state ==
assert.c:0(.annobin_assert.c_end)[0x7f33d8df8a76]
sql/my_json_writer.cc:380(Single_line_formatting_helper::on_add_member(char const*, unsigned long))[0x558362f6a717]
sql/my_json_writer.cc:150(Json_writer::add_member(char const*, unsigned long))[0x558362f69a91]
sql/my_json_writer.cc:146(Json_writer::add_member(char const*))[0x558362f69a5f]
sql/my_json_writer.h:383(Json_writer_object::Json_writer_object(THD*, char const*))[0x558362ceccaa]
sql/opt_range.cc:5139(get_best_disjunct_quick(PARAM*, SEL_IMERGE*, double))[0x5583632407d0]
sql/opt_range.cc:3000(SQL_SELECT::test_quick_select

This fixes up commit d22c8cae

The previous threads locked need to be released too.

This occurs if the initialization of any of the non-first
mutex/conditition variables errors occurs.

Fix a bug of unreleased lock ctrl_mutex in the method create_worker_threads

added summary/description per package.

When transaction creates or drops temporary tables and afterward its statement
faces an error even the transactional table statement's cached ROW
format events get involved into binlog and are visible after the transaction's commit.

Fixed with proper analysis of whether the errored-out statement needs
to be rolled back in binlog.
For instance a fact of already cached CREATE or DROP for temporary
tables by previous statements alone
does not cause to retain the being errored-out statement events in the
cache.
Conversely, if the statement creates or drops a temporary table
itself it can't be rolled back - this rule remains.