During native table rebuild or index creation, InnoDB used to skip
redo logging and write MLOG_INDEX_LOAD records to inform crash recovery
and Mariabackup of the gaps in redo log. This is fragile and prohibits
some optimizations, such as skipping the doublewrite buffer for
newly (re)initialized pages (MDEV-19738).

row_merge_write_redo(): Remove. We do not write MLOG_INDEX_LOAD
records any more. Instead, we write full redo log.

FlushObserver: Remove.

fseg_free_page_func(): Remove the parameter log. Redo logging
cannot be disabled.

fil_space_t::redo_skipped_count: Remove.

We cannot remove buf_block_t::skip_flush_check, because PageBulk
will temporarily generate invalid B-tree pages in the buffer pool.

Let us define page_id_t as a thin wrapper of uint64_t so that
the comparison operators can be simplified. This is a follow-up
to the original commit 14be8143.

The comparison operator for recv_sys.pages.emplace() turned out to be
a busy spot in a recovery benchmark. That data structure was introduced
in MDEV-19586 in commit 177a571e.

The linear scan of recv_sys_t::blocks() in recv_sys_t::free()
turns out to dominate the execution time in crash recovery.
Let us scan the much shorter buf_pool->chunks lists instead.

MDEV-20051: Add new mode to wsrep_OSU_method in which Galera checks storage engine of the effected table

Introduced a new wsrep_strict_ddl configuration variable in which
Galera checks storage engine of the effected table. If table is not
InnoDB (only storage engine currently fully supporting Galera
replication) DDL-statement will return error code:

ER_GALERA_REPLICATION_NOT_SUPPORTED
       eng "DDL-statement is forbidden as table storage engine does not support Galera replication"

However, when wsrep_replicate_myisam=ON we allow DDL-statements to
MyISAM tables. If effected table is allowed storage engine Galera
will run normal TOI.

This new setting should be for now set globally on all
nodes in a cluster. When this setting is set following DDL-clauses
accessing tables not supporting Galera replication are refused:

* CREATE TABLE (e.g. CREATE TABLE t1(a int) engine=Aria
* ALTER TABLE
* TRUNCATE TABLE
* CREATE VIEW
* CREATE TRIGGER
* CREATE INDEX
* DROP INDEX
* RENAME TABLE
* DROP TABLE

Statements on PROCEDURE, EVENT, FUNCTION are allowed as effected
tables are known only at execution. Furthermore, USER, ROLE, SERVER,
DATABASE statements are also allowed as they do not really have
effected table.

ANding of the range built from inferred NOT NULL conditions and the range
built from other conditions used in WHERE/ON clauses may produce an
IMPOSSIBLE range. The code of MDEV-15777 did not take into account this
possibility.

Rewriting GRANT/REVOKE grammar to use more bison stack and use Sql_cmd_ style

1. Removing a few members from LEX:
   - uint grant, grant_to_col, which_columns
   - List<LEX_COLUMN> columns
   - bool all_privileges
2. Adding classes Grand_object_name, Lex_grant_object_name
3. Adding classes Grand_privilege, Lex_grand_privilege
4. Adding struct Lex_column_list_privilege_st, class Lex_column_list_privilege
5. Rewriting the GRANT/REVOKE grammar to use new classes and pass them through
   bison stack (rather than directly access LEX members)
6. Adding classes Sql_cmd_grant* and Sql_cmd_revoke*,
   changing GRANT/REVOKE to use LEX::m_sql_cmd.
7. Adding the "sp_handler" grammar rule and removing some duplicate grammar
   for GRANT/REVOKE for different kinds of SP objects.
8. Adding a new rule comma_separated_ident_list, reusing it in:
   - with_column_list
   - colum_list_privilege

ut_align_down(): Preserve the const qualifier. Use C++ casts.

ha_delete_hash_node(): Correct an assertion expression.

fil_page_get_type(): Perform an assumed-aligned read.

page_align(): Preserve the const qualifier. Assume (some) alignment.

page_get_max_trx_id(): Check the index page type.

page_header_get_field(): Perform an assumed-aligned read.

page_get_autoinc(): Perform an assumed-aligned read.

page_dir_get_nth_slot(): Perform an assumed-aligned read.
Preserve the const qualifier.

recv_sys_t::ALIGNMENT: The recv_sys_t::alloc() alignment

When using LTO, one can see optimization of stack variables that
are passed to check_stack_overrun as argument buf. That prevents
proper stack overrun detection.

Add explicit casts when assigning ulint to m_user_space_id.

mtr_log_t and mtr_t::m_log_mode have the same range 0 to 3.

mtr_t::get_log_mode(): Use equivalent static_assert().

mtr_t::m_n_log_recs: Do not exceed the number of bits in uint16_t.

Use bit-fields for some mtr_t members to improve locality of reference.
Because mtr_t is never shared between threads, there are no considerations
regarding concurrent access.

Since commit 5e62b6a5 (MDEV-16264),
purge_sys_t::stop() no longer waited for all purge activity to stop.

This caused problems on FLUSH TABLES...FOR EXPORT because of
purge running concurrently with the buffer pool flush.
The assertion at the end of buf_flush_dirty_pages() could fail.

The, implemented by Vladislav Vaintroub, aims to eliminate race
conditions when stopping or resuming purge:

waitable_task::disable(): Wait for the task to complete, then replace
the task callback function with noop.

waitable_task::enable(): Restore the original task callback function
after disable().

purge_sys_t::stop(): Invoke purge_coordinator_task.disable().

purge_sys_t::resume(): Invoke purge_coordinator_task.enable().

purge_sys_t::running(): Add const qualifier, and clarify the comment.
The purge coordinator task will remain active as long as any purge
worker task is active.

purge_worker_callback(): Assert purge_sys.running().

srv_purge_wakeup(): Merge with the only caller purge_sys_t::resume().

purge_coordinator_task: Use static linkage.

srv_export_innodb_status(): While gathering
innodb_mem_adaptive_hash, acquire btr_search_latches[i]
in order to prevent a race condition with buffer pool resizing.

Release memory as soon as redo log records are processed.

Because the memory allocation and deallocation of parsed redo log
records must be protected by recv_sys.mutex, it is better to avoid
using a std::atomic field for bookkeeping.

buf_page_t::access_time: Keep track of the recv_sys.pages record
allocations. The most significant 16 bits will count allocated
blocks (which were previously counted by buf_page_t::buf_fix_count
in the debug version), and the least significant 16 bits indicate
the number of allocated bytes in the block (which was previously
managed in buf_block_t::modify_clock), which must be a positive
number, up to innodb_page_size. The byte offset 65536 is represented
as the value 0.

recv_recover_page(): Let the caller erase the log.

recv_validate_tablespace(): Acquire recv_sys_t::mutex.

MDEV-21616: Server crash when using "SET STATEMENT max_statement_time=0 FOR desc xxx" lead to collapse

Main select should be pushed first.

row_log_table_get_pk_old_col(): For replacing a NULL value for a
column of the being-added primary key, look up the correct
default value, even if columns had been instantly reordered or
dropped earlier. This ought to have been broken ever since
commit 0e5a4ac2 (MDEV-15562).

Function `signal_waiters` assigned `m_committed_seqno` variable outside of
mutex lock which caused incorrect behavior of WSREP_SYNC_WAIT_UPTO_GTID.
Fixed by moving assignment inside lock. Added handling of OOM and now
error is reported.
Remove hard-coded seqno value and read seqno directly from current node state.

Also added support for MAP_SYNC. It allows to achieve decent performance
with DAX devices even when libpmem is unavailable.

Fixed Windows version of my_msync(): according to manual FlushViewOfFile()
may return before flush is actually completed. It is advised to issue
FlushFileBuffers() after FlushViewOfFile().

ha_innobase::commit_inplace_alter_table(): After
ALTER_STORED_COLUMN_ORDER, ensure that the virtual column metadata
will be reloaded also when the table is not being rebuilt.

Fix:
===
Add "REPLICA" as an alias for "SLAVE". All commands which use "SLAVE" keyword
can be used with new alias "REPLICA".

List of commands:

On Master:
=========
SHOW REPLICA HOSTS <--> SHOW SLAVE HOSTS
Privilege "SLAVE"  <--> "REPLICA"

On Slave:
=========
START SLAVE       <--> START REPLICA
START ALL SLAVES  <--> START ALL REPLICAS
START SLAVE UNTIL <--> START REPLICA UNTIL
STOP SLAVE        <--> STOP REPLICA
STOP ALL SLAVES   <--> STOP ALL REPLICAS
RESET SLAVE       <--> RESET REPLICA
RESET SLAVE ALL   <--> RESET REPLICA ALL
SLAVE_POS         <--> REPLICA_POS

We need to release global system variables mutex before
doing wsrep_init to avoid race with next show status and
we need to save wsrep_on value as it is changed on wsrep_init.
Added test case.

When wsrep_on is changed to ON we might need to run wsrep_init
if wsrep-provider is set and wsrep is not inited.

MDEV-20001 Potential dangerous regression: INSERT INTO >=100 rows fail for myisam table with HASH indexes

Problem:-

So the issue is when we do bulk insert with rows
> MI_MIN_ROWS_TO_DISABLE_INDEXES(100) , We try to disable the indexes to
speedup insert. But current logic also disables the long unique indexes.

Solution:- In ha_myisam::start_bulk_insert if we find long hash index
(HA_KEY_ALG_LONG_HASH) we will not disable the index.

This commit also refactors the mi_disable_indexes_for_rebuild function,
Since this is function is called at only one place, it is inlined into
start_bulk_insert

mi_clear_key_active is added into myisamdef.h because now it is also used
in ha_myisam.cc file.

(Same is done for Aria Storage engine)

If we have long unique key for aria engine return too long key error, because
Aria does not support key on virtual generated column.

main change: rename first redo log without file close

second change: use os_offset_t to represent offset in a file

third change: fix log texts

Starting with MariaDB Server 10.4, C++11 is being used.
Hence, std::atomic should be preferred to my_atomic.

Fix up commit f5c080c7

In commit 0e5a4ac2 (MDEV-15562)
we introduced was a bogus debug check failure that does not affect
the correctness of the release build.

With a fixed-length PRIMARY KEY, we do not have to recompute
the rec_get_offsets() after restarting the mini-transaction,
because the offsets of DB_TRX_ID,DB_ROLL_PTR are not going
to change.

row_undo_mod_clust(): Invoke rec_offs_make_valid() to keep the
debug check in page_zip_write_trx_id_and_roll_ptr() happy.

The scenario to reproduce this bug should be rather unlikely:
In the time frame when row_undo_mod_clust() has committed its
first mini-transaction and has not yet started the next one,
another mini-transaction must do something that causes the page
to be reorganized, split or merged.

The variable 'dlh' was being used uninitialized if WSREP_PROVIDER
is not set.

Variable `wsrep_new_cluster` should be set to false after `wsrep_init_startup`.
Problem was that this was done before when mysqldump is used as SST method so option
wsrep-new-cluster didn't have any effect.