some trivial simplifications. drinking the ocean,
one drop at a time

MDEV-11552 Queries executed by event scheduler are written to slow log incorrectly or not written at all

because thd->update_server_status() is used to measure the query time
for the slow log (not only to set protocol level flags),
it needs to be called also when the server isn't going to send
anything to the client.

        MySQL has a bug failing to handle
           MYSQL_THDVAR_STR(...  PLUGIN_VAR_NOSYSVAR |
                                 PLUGIN_VAR_NOCMDOPT | PLUGIN_VAR_MEMALLOC)
        so fall back to just PLUGIN_VAR_READONLY | PLUGIN_VAR_MEMALLOC
        whem MySQL started.

MDEV-10713: signal 11 error on multi-table update - crash in handler::increment_statistics or in make_select or assertion failure pfs_thread == ((PFS_thread*) pthread_getspecific((THR_PFS)))

Different fix. Don't allow Item_func_sp to be evaluated unless
all tables are prelocked.

Extend the test case to make sure Item_func_sp::val_str is called
(the table must have at least one row for that).

Revert "MDEV-10713: signal 11 error on multi-table update - crash in handler::increment_statistics or in make_select or assertion failure pfs_thread == ((PFS_thread*) pthread_getspecific((THR_PFS)))"

This reverts commit 035a5ac6.

Two minor problems and one regression:
1. caching the value in str_result. Other Item methods may use it,
   destroying the cache. See, for example, Item::save_in_field, where
   str_result is moved to use a local buffer (this failed main.grant)
2. Item_func_conv_charset::safe is now set too late, it's initialized
   only in val_str() but checked before that, this failed many tests
   in optimized builds.

to fix 1 - use tmp_result instead of str_result, to fix 2, use
the else branch in the Item_func_conv_charset constructor to set
safe purely from charset properties.

But this introduces a regression, constant strings can no longer be
converted, say, from utf8 to latin1 (because 'safe' will be false).
This fails few tests too. There is no way to fix it without reverting
the commit and converting constants, as before, in the constructor.

truncate unused IO_CACHE backing store files in binlog_cache_data
to release the disk space they were occupying

        Rpl_filter::parse_filter_rule() made NULL-safe.

check for VIEW/DERIVED fields

MDEV-10713: signal 11 error on multi-table update - crash in handler::increment_statistics or in make_select or assertion failure pfs_thread == ((PFS_thread*) pthread_getspecific((THR_PFS)))

Move expression execution out of Item constructor.

Exclude untouched in prepare phese subqueries from the select/unit tree
because they became unreachable by execution.

The problem was that null_value was not set to "false" on a well-formed row.
If an ill-formed row was followed by a well-forned row, null_value remained
"true" in the call of Item::send() for the well-formed row.

Check for readline before checking for curses headers, because
MYSQL_CHECK_READLINE fails when curses is not found, but
CHECK_INCLUDE_FILES simply remembers the fact and continues.  So if
there's no curses, MYSQL_CHECK_READLINE will abort, the user will then
installs curses and continue the build. Thus, CHECK_INCLUDE_HEADERS
will remember that there is no curses, but other checks from
MYSQL_CHECK_READLINE will remember that curses are there. It will
result in inconsistent HAVE_xxx defines.

Don't assume that a word of n bytes can match a word of
at most n * charset->mbmaxlen bytes, always go for the worst.

MDEV-11171 Assertion `m_cpp_buf <= ptr && ptr <= m_cpp_buf + m_buf_length' failed in Lex_input_stream::body_utf8_append(const char*, const char*)

The flag TABLE_LIST::fill_me must be reset to false at the prepare
phase for any materialized derived table used in the executed query.
Otherwise if the optimizer decides to generate a key for such a table
it is generated only for the first execution of the query.

Skip  permission for data directory for LogonUser, if installation
runs by one of the service accounts (determined from their well-known SID).
There is no real LogonUser in this case.

- new location of signtool
- silence a nonsensical warning from stl  header
(complain about noexcept() function attribute, if /EHsc is not set)

mysqldump/mysql_install_db.exe fail

The bug is described in
https://connect.microsoft.com/VisualStudio/Feedback/Details/1902345

When reading from a pipe in text mode, using CRT function such as fread(),
some newlines may be lost. Workaround is to use binary mode on reading side
and if necessary, replace \r\n with \n.

Patch provided by Honza Horak

don't let identifiers with new lines to break a comment

pass them through as is

* use proper sql quoting rules for USE, while preserving
  as much of historical behavior as possible
* short commands (\u) behave as before

when they're not needed anymore. Helps when
daemonizing it from mysql.init

              RESTRICTED IN ALL GA RELEASES

Back port of WL#6782 to 5.5 and 5.6. This also includes
back port of Bug#20771331, Bug#20741572 and Bug#20770671.
Bug#24695274 and Bug#24679907 are also handled along with
this.

Also add fallback version string for unknown future versions.

Ensure atomic appends to the error log by using CreateFile with
FILE_APPEND_DATA flag to open error log file (both MTR and server)