row_search_mvcc(): Duplicate the logic of btr_pcur_move_to_next()
so that an infinite loop can be avoided when advancing to the next
page fails due to a corrupted page.

Also, --skip-innodb-buffer-pool-load-at-startup to avoid a crash
in buf_load() due to loading pages that we are corrupting intentionally.

At higher levels of innodb_force_recovery, the InnoDB transaction
subsystem will not be set up at all.

At slightly lower levels, recovered transactions will not be rolled back,
and DDL operations could hang due to locks being held at all.

Let us consistently refuse all writes if the predicate
high_level_read_only holds. We failed to refuse DROP TABLE
and DROP DATABASE. (Refusing DROP TABLE is a partial backport
from MDEV-19570 in the 10.5 branch.)

- Replace mysql_version check with omit_virtual_cols() in
ha_innobase::check_if_supported_inplace_alter().

- If one of the encryption threads already started the initialization
of the tablespace then don't remove the other uninitialized tablespace
from the rotation list.

- If there is a change in innodb_encrypt_tables then
don't remove the processed tablespace from rotation list.

LOCK_global_system_variables: Declare with MYSQL_PLUGIN_IMPORT

- Don't apply redo log for the corrupted page when innodb_force_recovery > 0.
- Allow the table to be dropped when index root page is
corrupted when innodb_force_recovery > 0.

The update callback functions for several settable global InnoDB variables
are acquiring InnoDB latches while holding LOCK_global_system_variables.

On the other hand, some InnoDB code is invoking THDVAR() while holding
InnoDB latches. An example of this is thd_lock_wait_timeout() that is
called by lock_rec_enqueue_waiting(). In some cases, the
intern_sys_var_ptr() that is invoked by THDVAR() may acquire
LOCK_global_system_variables, via sync_dynamic_session_variables().

In lock_rec_enqueue_waiting(), we really must be holding some InnoDB
latch while invoking THDVAR(). This implies that
LOCK_global_system_variables must conceptually reside below any InnoDB
latch in the latching order. That in turns implies that the various
update callback functions must release LOCK_global_system_variables
before acquiring any InnoDB mutexes or rw-locks, and reacquire
LOCK_global_system_variables later. The validate functions are being
invoked while not holding LOCK_global_system_variables and thus they
do not need any changes.

The following statements are affected by this:

SET GLOBAL innodb_adaptive_hash_index = …;
SET GLOBAL innodb_cmp_per_index_enabled = 1;
SET GLOBAL innodb_old_blocks_pct = …;
SET GLOBAL innodb_fil_make_page_dirty_debug = …; -- debug builds only
SET GLOBAL innodb_buffer_pool_evict = uncompressed; -- debug builds only
SET GLOBAL innodb_purge_run_now = 1; -- debug builds only
SET GLOBAL innodb_purge_stop_now = 1; -- debug builds only
SET GLOBAL innodb_log_checkpoint_now = 1; -- debug builds only
SET GLOBAL innodb_buf_flush_list_now = 1; -- debug builds only
SET GLOBAL innodb_buffer_pool_dump_now = 1;
SET GLOBAL innodb_buffer_pool_load_now = 1;
SET GLOBAL innodb_buffer_pool_load_abort = 1;
SET GLOBAL innodb_status_output = …;
SET GLOBAL innodb_status_output_locks = …;
SET GLOBAL innodb_encryption_threads = …;
SET GLOBAL innodb_encryption_rotate_key_age = …;
SET GLOBAL innodb_encryption_rotation_iops = …;
SET GLOBAL innodb_encrypt_tables = …;
SET GLOBAL innodb_disallow_writes = …;

buf_LRU_old_ratio_update(): Correct the return type.

or server crashes in JOIN::fix_all_splittings_in_plan after EXPLAIN

This patch resolves the problem of overflowing when performing
calculations to estimate the cost of an evaluated query execution plan.
The overflowing in a non-debug build could cause different kind of
problems uncluding crashes of the server.

- create_table_def() misconstructs the dict_table_t by ignoring the stored
columns of the table if virtual column is present between stored columns.

Simulation of a big-sized event in rpl.rpl_semi_sync_skip_repl did not clean
up after itself so screw the last binlog event offset which could jump
backwards.
The test is refined to rotate a binlog file with simulation and use the next
one for logics of the test incl master-slave synchonization.

MDEV-14192: mariabackup.incremental_backup failed in buildbot with Failing assertion: byte_offset % OS_FILE_LOG_BLOCK_SIZE == 0

In some cases it's possible that InnoDB redo log file header is re-written so,
that checkpoint lsn and checkpoint lsn offset are updated, but checkpoint
number stays the same. The fix is to re-read redo log header if at least one
of those three parametes is changed at backup start.

Repeat the logic of log_group_checkpoint() on choosing InnoDB checkpoint info
field on backup start. This does not influence backup correctness, but
simplifies bugs analysis.

The INFORMATION_SCHEMA plugin INNODB_SYS_VIRTUAL, which was introduced
in MariaDB 10.2.2 along with the dictionary table SYS_VIRTUAL,
is similar to other, much older and already stable plugins that
provide access to InnoDB dictionary tables.

This patch corrects the patch for the bug 10006. The latter incorrectly
calculates the attribute TABLE_LIST::dep_tables for inner tables
of outer joins that are to be converted into inner joins.
As a result after the patch some valid join orders were not evaluated
and the optimizer could choose an execution plan that was far from
being optimal.

Running trigger_null-8605 drop_bad_db_type tests in this order was
failing due to unremoved temporary files created in trigger_null-8605

The code in best_access_path function, when it does not find a key suitable for ref access
and join_cache_level is set to a value so that hash_join is possible we build a hash key.
Later in the function we compare the cost of ref access with table scan (or index scan
or quick selects). No need to do this when we have got the hash key.

post-merge changes

Closes #954

This patch is for MEM_ROOT only.
In debug mode add 8 byte of poisoned memory before every allocated chunk.
On the right of every chunk there will be either 1-7 trailing poisoned bytes, or
next chunk's redzone, or poisoned non allocated memory or redzone of a
malloc()ed buffer.

thread_pool_server_audit.result fixed.

btr_pcur_move_to_last_on_page(): Merge with the only caller.

Problem:
========
The test now fails with the following trace:

CURRENT_TEST: rpl.rpl_parallel_temptable
--- /mariadb/10.4/mysql-test/suite/rpl/r/rpl_parallel_temptable.result
+++ /mariadb/10.4/mysql-test/suite/rpl/r/rpl_parallel_temptable.reject
@@ -194,7 +194,6 @@
 30    conservative
 31    conservative
 32    optimistic
-33    optimistic

Analysis:
=========
The part of test which fails with result content mismatch is given below.

CREATE TEMPORARY TABLE t4 (a INT PRIMARY KEY) ENGINE=InnoDB;
INSERT INTO t4 VALUES (32);
INSERT INTO t4 VALUES (33);
INSERT INTO t1 SELECT a, "optimistic" FROM t4;

slave_parallel_mode=optimistic

The expectation of the above test script is, INSERT FROM SELECT should read both
32, 33 and populate table 't1'. But this expectation fails occasionally.

All three INSERT statements are handed over to three different slave parallel
workers. Temporary tables are not safe for parallel replication. They were
designed to be visible to one thread only, so have no table locking.  Thus there
is no protection against two conflicting transactions committing in parallel and
things like that.

So anything that uses temporary tables will be serialized with anything before
it, when using parallel replication by using a "wait_for_prior_commit" function
call. This will ensure that the each transaction is executed sequentially.

But there exists a code path in which the above wait doesn't happen.  Because of
this at times INSERT from SELECT doesn't wait for the INSERT (33) to complete
and it completes its executes and enters commit stage.  Hence only row 32 is
found in those cases resulting in test failure.

The wait needs to be added within "open_temporary_table" call. The code looks
like this within "open_temporary_table".

Each thread tries to open temporary table in 3 different ways:

case 1: Find a temporary table which is already in use by using
         find_temporary_table(tl) && wait_for_prior_commit()
case 2: If above failed then try to look for temporary table which is marked for
        free for reuse. This internally calls "wait_for_prior_commit()" if table
        is found.
         find_and_use_tmp_table(tl, &table)
case 3: If none of the above open a new table handle from table share.
         if (!table && (share= find_tmp_table_share(tl)))
         { table= open_temporary_table(share, tl->get_table_name(), true); }

At present the "wait_for_prior_commit" happens only in case 1 & 2.

Fix:
====
On slave add a call for "wait_for_prior_commit" for case 3.

The above wait on slave will solve the issue. A more detailed fix would be to
mark temporary tables as not safe for parallel execution on the master side.
In order to do that, on the master side, mark the Gtid_log_event specific flag
FL_TRANSACTIONAL to be false all the time. So that they are not scheduled
parallely.

Fix for the SET GLOBAL server_audit_loggin=on; added.

This patch complements the original patch for MDEV-18896 that prevents
conversions to semi-joins in tableless selects used in INSERT statements
in post-5.5 versions of the server.
The test case was corrected as well to ensure that potential conversion
to jtbm semi-joins is also checked (the problem was that one of
the preceeding testcases in subselect_sj.test did not restore the
state of the optimizer switch leaving the 'materialization' in the state
'off' and so blocking this check).
Noticed an inconsistency in the state of select_lex::table_list used
in INSERT statements and left a comment about this.

Crash was timeout crash. Add correct waits for connections, wsrep
sync waits and auto increment offset save and restore.

Use wsrep sync wait instead of unnecessary waits and
correct slave setting.

Remove unnecessary sleeps and fix wait_condition to use
wsrep_flow_control_paused i.e. we wait until flow control
pauses a transaction on master.

JSON_MERGE_PATCH implemented. Added JSON_MERGE_PRESERVE as a synonim for
the JSON_MERGE.