In commit e71e6133 (MDEV-24671),
lock_sys.wait_mutex was moved above lock_sys.mutex
(which was later replaced with lock_sys.latch) in the latching order.

In commit 7cf4419f (MDEV-24789),
a potential hang was introduced to Galera. The function lock_wait()
would hold lock_sys.wait_mutex while invoking wsrep_is_BF_lock_timeout(),
which in turn could acquire LockMutexGuard for some diagnostic printout.

wsrep_is_BF_lock_timeout(): Do not invoke trx_print_latched() or
LockMutexGuard.

lock_sys_t::wr_lock(), lock_sys_t::rd_lock(): Assert that the current
thread is not holding lock_sys.wait_mutex.
Unfortunately, RW-locks are not covered by SAFE_MUTEX.

Reviewed by: Jan Lindström

Imported the following tests from Oracle MySQL:

* mysql-test/t/locking_clause.test
* mysql-test/suite/innodb/t/skip_locked_nowait.test
* mysql-test/t/locking_part.test

Ported to MariaDB by Daniel Black, changes include:
* Removed 'FOR SHARE OF /FOR UPDATE OF' tests that are part of
  MDEV-17514 (not yet implemented)
* mysql-test/t/locking_clause.test removes broken the limit test (outstanding MDEV-25244) bug.
* mysql-test/suite/innodb/t/skip_locked_nowait.test - removed high
  priority transactions
* mysql-test/t/locking_part.test imported to mysql-test/suite/innodb/t/partition_locking.test
  changed ER_LOCK_NOWAIT -> ER_LOCK_WAIT_TIMEOUT consistent with already
  implemented WAIT/NOWAIT feature. Changed "FOR SHARE SKIP LOCKED" ->
  "LOCK IN SHARE MODE SKIP LOCKED".

Adds an implementation for SELECT ... FOR UPDATE SKIP LOCKED /
SELECT ... LOCK IN SHARED MODE SKIP LOCKED

This is implemented only InnoDB at the moment, not in RockDB yet.

This adds a new hander flag HA_CAN_SKIP_LOCKED than
will be used when the storage engine advertises the flag.

When a storage engine indicates this flag it will get
TL_WRITE_SKIP_LOCKED and TL_READ_SKIP_LOCKED transaction types.

The Lex structure has been updated to store both the FOR UPDATE/LOCK IN
SHARE as well as the SKIP LOCKED so the SHOW CREATE VIEW
implementation is simplier.

"SELECT FOR UPDATE ... SKIP LOCKED" combined with CREATE TABLE AS or
INSERT.. SELECT on the result set is not safe for STATEMENT based
replication. MIXED replication will replicate this as row based events."

Thanks to guidance from Facebook commit
https://github.com/facebook/mysql-5.6/commit/193896c466d43fd905a62a60f1d73fd9c551a6e4
This helped verify basic test case, and components that need implementing
(even though every part was implemented differently).

Thanks Marko for guidance on simplier InnoDB implementation.

Reviewers: Marko, Monty

Use < TL_FIRST_WRITE for determining a READ transaction.

Use TL_FIRST_WRITE as the relative operator replacing TL_WRITE_ALLOW_WRITE
as the minimium WRITE lock type.

MDEV-25334 FTWRL/Backup blocks DDL on temporary tables with binlog enabled, assertion fails in Diagnostics_area::set_error_status

Fixed by adding a MDL_BACKUP_COMMIT lock before altering temporary tables
whose creation was logged to binary log (in which case the ALTER TABLE
must also be logged)

A consistency check for fil_space_t::name is causing recovery failures
in MDEV-25180 (Atomic ALTER TABLE). So, we'd better remove that field
altogether.

fil_space_t::name was more or less a copy of dict_table_t::name
(except for some special cases), and it was not being used for
anything useful.

There used to be a name_hash, but it had been removed already in
commit a75dbfd7 (MDEV-12266).

We will also remove os_normalize_path(), OS_PATH_SEPARATOR,
OS_PATH_SEPATOR_ALT. On Microsoft Windows, we will treat \ and /
roughly in the same way. The intention is that for per-table
tablespaces, the filenames will always follow the pattern
prefix/databasename/tablename.ibd. (Any \ in the prefix must not
be converted.)

ut_basename_noext(): Remove (unused function).

read_link_file(): Replaces RemoteDatafile::read_link_file().
We will ensure that the last two path component separators are
forward slashes (converting up to 2 trailing backslashes on
Microsoft Windows), so that everywhere else we can
assume that data file names end in "/databasename/tablename.ibd".

Note: On Microsoft Windows, path names that start with \\?\ must
not contain / as path component separators. Previously, such paths
did work in the DATA DIRECTORY argument of InnoDB tables.

Reviewed by: Vladislav Vaintroub

Problem:

The problem happened because of a conceptual flaw in the server code:

a. The table level CHARSET/COLLATE clause affected all data types,
  including numeric and temporal ones:

   CREATE TABLE t1 (a INT) CHARACTER SET utf8 [COLLATE utf8_general_ci];

  In the above example, the Column_definition_attributes
  (and then the FRM record) for the column "a" erroneously inherited
  "utf8" as its character set.

b. The "ALTER TABLE t1 CONVERT TO CHARACTER SET csname" statement
   also erroneously affected Column_definition_attributes::charset
   for numeric and temporal data types and wrote "csname" as their
   character set into FRM files.

So now we have arbitrary non-relevant charset ID values for numeric
and temporal data types in all FRM files in the world :)

The code in the server and the other engines did not seem to be affected
by this flaw. Only InnoDB inplace ALTER was affected.

Solution:

Fixing the code in the way that only character string data types
(CHAR,VARCHAR,TEXT,ENUM,SET):
- inherit the table level CHARSET/COLLATE clause
- get the charset value according to "CONVERT TO CHARACTER SET csname".

Numeric and temporal data types now always get &my_charset_numeric
in Column_definition_attributes::charset and always write its ID into FRM files:
- no matter what the table level CHARSET/COLLATE clause is, and
- no matter what "CONVERT TO CHARACTER SET" says.

Details:

1. Adding helper classes to pass small parts of HA_CREATE_INFO
   into Type_handler methods:

   - Column_derived_attributes - to pass table level CHARSET/COLLATE,
     so columns that do not have explicit CHARSET/COLLATE clauses
     can derive them from the table level, e.g.

       CREATE TABLE t1 (a VARCHAR(1), b CHAR(1)) CHARACTER SET utf8;

   - Column_bulk_alter_attributes - to pass bulk attribute changes
     generated by the ALTER related code. These bulk changes affect
     multiple columns at the same time:

       ALTER TABLE ... CONVERT TO CHARACTER SET csname;

   Note, passing the whole HA_CREATE_INFO directly to Type_handler
   would not be good: HA_CREATE_INFO is huge and would need not desired
   dependencies in sql_type.h and sql_type.cc. The Type_handler API should
   use smallest possible data types!

2. Type_handler::Column_definition_prepare_stage1() is now responsible
   to set Column_definition::charset properly, according to the data type,
   for example:

   - For string data types, Column_definition_attributes::charset is set from
     the table level CHARSET/COLLATE clause (if not specified explicitly in
     the column definition).

   - For numeric and temporal fields, Column_definition_attributes::charset is
     set to &my_charset_numeric, no matter what the table level
     CHARSET/COLLATE says.

   - For GEOMETRY, Column_definition_attributes::charset is set to
     &my_charset_bin, no matter what the table level CHARSET/COLLATE says.

   Previously this code (setting `charset`) was outside of of
   Column_definition_prepare_stage1(), namely in
   mysql_prepare_create_table(), and was erroneously called for
   all data types.

3. Adding Type_handler::Column_definition_bulk_alter(), to handle
   "ALTER TABLE .. CONVERT TO". Previously this code was inside
   get_sql_field_charset() and was erroneously called for all data types.

4. Removing the Schema_specification_st parameter from
   Type_handler::Column_definition_redefine_stage1().
   Column_definition_attributes::charset is now fully properly initialized by
   Column_definition_prepare_stage1(). So we don't need access to the
   table level CHARSET/COLLATE clause in Column_definition_redefine_stage1()
   any more.

5. Other changes:
   - Removing global function get_sql_field_charset()

   - Moving the part of the former get_sql_field_charset(), which was
     responsible to inherit the table level CHARSET/COLLATE clause to
     new methods:
      -- Column_definition_attributes::explicit_or_derived_charset() and
      -- Column_definition::prepare_charset_for_string().
     This code is only needed for string data types.
     Previously it was erroneously called for all data types.

   - Moving another part, which was responsible to apply the
     "CONVERT TO" clause, to
     Type_handler_general_purpose_string::Column_definition_bulk_alter().

   - Replacing the call for get_sql_field_charset() in sql_partition.cc
     to sql_field->explicit_or_derived_charset() - it is perfectly enough.
     The old code was redundant: get_sql_field_charset() was called from
     sql_partition.cc only when there were no a "CONVERT TO CHARACTER SET"
     clause involved, so its purpose was only to inherit the table
     level CHARSET/COLLATE clause.

   - Moving the code handling the BINCMP_FLAG flag from
     mysql_prepare_create_table() to
     Column_definition::prepare_charset_for_string():
     This code is responsible to resolve the BINARY comparison style
     into the corresponding _bin collation, to do the following transparent
     rewrite:
        CREATE TABLE t1 (a VARCHAR(10) BINARY) CHARSET utf8;  ->
        CREATE TABLE t1 (a VARCHAR(10) CHARACTER SET utf8 COLLATE utf8_bin);
     This code is only needed for string data types.
     Previously it was erroneously called for all data types.

6. Renaming Table_scope_and_contents_source_pod_st::table_charset
   to alter_table_convert_to_charset, because the only purpose it's used for
   is handlering "ALTER .. CONVERT". The new name is much more self-descriptive.

SI_USER is, however in FreeBSD there are a couple of non-kernel
user signal infomations above SI_KERNEL.

Put a fallback just in case there is nothing available.

Added handling for sql_safe_updated i.e. we disable it while
we do wsrep_schema operations.

MDEV-17913 Encrypted transactional Aria tables remain corrupt after crash recovery, automatic repairment does not work

This was because of a wrong test in encryption code that wrote random
numbers over the LSN for pages for transactional Aria tables during repair.
The effect was that after an ALTER TABLE ENABLE KEYS of a encrypted
recovery of the tables would not work.

Fixed by changing testing of !share->now_transactional to
!share->base.born_transactional.

Other things:
- Extended Aria check_table() to check for wrong (= too big) LSN numbers.
- If check_table() failed just because of wrong LSN or TRN numbers,
  a following repair table will just do a zerofill which is much faster.
- Limit number of LSN errors in one check table to MAX_LSN_ERROR (10).
- Removed old obsolete test of 'if (error_count & 2)'. Changed error_count
  and warning_count from bits to numbers of errors/warnings as this is
  more useful.

`WSREP_CLIENT` is used as condition for starting ALTER/OPTIMIZE/REPAIR TOI.
Using this condition async replicated affected DDL's will not be replicated.
Fixed by removing this condition.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

This patch makes the following changes around variable wsrep_on:

1) Variable wsrep_on can no longer be updated from a session that has
an active transaction running. The original behavior allowed cases
like this:

     BEGIN;
     INSERT INTO t1 VALUES (1);
     SET SESSION wsrep_on = OFF;
     INSERT INTO t1 VALUES (2);
     COMMIT;

With regular transactions this would result in no replication
events (not even value 1). With streaming replication it would be
unnecessarily complex to achieve the same behavior. In the above
example, it would be possible for value 1 to be already replicated if
it happened to fill a separate fragment, while value 2 wouldn't.

2) Global variable wsrep_on no longer affects current sessions, only
subsequent ones. This is to avoid a similar case to the above, just
using just by using global wsrep_on instead session wsrep_on:

      --connection conn_1
      BEGIN;
      INSERT INTO t1 VALUES(1);

      --connection conn_2
      SET GLOBAL wsrep_on = OFF;

      --connection conn_1
      INSERT INTO t1 VALUES(2);
      COMMIT;

The above example results in the transaction to be replicated, as
global wsrep_on will only affect the session wsrep_on of new
connections.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

MDEV-17913 Encrypted transactional Aria tables remain corrupt after crash recovery, automatic repairment does not work

This was because of a wrong test in encryption code that wrote random
numbers over the LSN for pages for transactional Aria tables during repair.
The effect was that after an ALTER TABLE ENABLE KEYS of a encrypted
recovery of the tables would not work.

The test cases will be pushed into 10.5 as it requires of several changes
to check table that safer not to backport.

log_flush_notify(): Restore the reload of log_requests.start that was
accidentally removed in commit 8c2e3259.

Thanks to Elena Stepanova for a test case (repeatedly running FLUSH LOGS
concurrently with InnoDB write transactions).

In commit 1bd41158 the intention
was to move the trx_t::is_wsrep() check to the caller of the function
wsrep_is_BF_lock_timeout().

Merge commit 176aaf93
accidentally broke the WITH_WSREP release build.

buf_page_get_low(): Do not try to re-evict the page if it is
multiply buffer-fixed.

In commit 7cffb5f6 (MDEV-23399)
a livelock was introduced. If multiple threads are concurrently
requesting the same secondary index leaf page in buf_page_get_low()
and innodb_change_buffering_debug is set, all threads would try
to evict the page in a busy loop, never succeeding because the
block is buffer-fixed by other threads.

Thanks to Roel Van de Paar for reporting the original failure and
Elena Stepanova for producing an "rr replay" trace.

rocksdb_checkpoint_request() should call FlushWAL(sync=true) (which does
write-out and sync), not just SyncWAL()  (which just syncs without writing
out)
Followup: the test requires debug sync facility

(This is a backport to 10.5)

The code compares two query plans with identical costs, the plan
with lateral is the same as one without. Introduce a small difference
to cost numbers to prefer non-lateral plan in this case.

Followup: the test requires debug sync facility

- Aborting of fulltext index creation fails to remove the
index from sys indexes table. When we try to reload the
table definition, InnoDB fails with index count mismatch
error. InnoDB should remove the index from sys indexes while
rollbacking the secondary index creation.

- Post push to address 32-bit build failure.

rocksdb_checkpoint_request() should call FlushWAL(sync=true) (which does
write-out and sync), not just SyncWAL()  (which just syncs without writing
out)