page_create(): Create normal B-tree pages. Callers that create
R-tree pages will set FIL_PAGE_TYPE and reset the split
sequence number afterwards.

The creation of ROW_FORMAT=COMPRESSED pages is unaffected;
they will be logged as compressed page images.

page_create_low(): Take const buf_block_t* as a parameter.
Let the callers invoke buf_block_modify_clock_inc().

btr_cur_upd_rec_sys(): Replaces row_upd_rec_sys_fields() and
implements redo logging.

row_upd_rec_sys_fields_in_recovery(): Remove, and merge to the
only remaining caller btr_cur_parse_update_in_place().

btr_cur_del_mark_set_clust_rec_log(),
btr_cur_del_mark_set_sec_rec_log(),
btr_cur_set_deleted_flag_for_ibuf():
Remove, and replace with btr_rec_set_deleted<bool>().

page_zip_rec_set_deleted(): Add the parameter mtr, and write a
MLOG_ZIP_WRITE_STRING record to the log.

Log the low-level operations for ROW_FORMAT=COMPRESSED index pages
using a new record, MLOG_ZIP_WRITE_STRING. We will still use
MLOG_1BYTE,..., MLOG_8BYTES or MLOG_WRITE_STRING for operations
on other than index pages (such as the page allocation bitmap pages).

We will stop writing the record MLOG_ZIP_PAGE_COMPRESS later, after
replacing all MLOG_REC_ and MLOG_COMP_REC_ that update index pages.

Log page reorganize as a series of insert operations.
This will make the redo log volume proportional to the page payload size.

btr_page_reorganize_low(): Add template <bool recovery=false>

btr_page_reorganize_block(): Remove the parameter 'bool recovery'

Instead of writing the high-level redo log records
MLOG_LIST_END_COPY_CREATED, MLOG_COMP_LIST_END_COPY_CREATED
write log for each individual insert of a record.

page_copy_rec_list_end_to_created_page(): Remove.

This will improve the fill factor of some pages.
Adjust some tests accordingly.

PageBulk::init(), PageBulk::finish(): Avoid setting bogus limits
to PAGE_HEAP_TOP and PAGE_N_DIR_SLOTS. Avoid accessor functions
that would enforce these limits before the correct ones are set
at the end of PageBulk::finish().

page_zip_reorganize(): Restore the page on failure.
In callers, omit now-redundant calls to page_zip_decompress().

btr_page_reorganize_low(): Define in static scope only, and
remove the z_level parameter. Assert that ROW_FORMAT is not COMPRESSED.

btr_page_reorganize_block(), btr_page_reorganize(): Invoke
page_zip_reorganize() for ROW_FORMAT=COMPRESSED.

trx_undof_page_add_undo_rec_log(): Remove.

trx_undo_page_set_next_prev_and_add(), trx_undo_page_report_modify(),
trx_undo_page_report_rename(): Write lower-level redo log records.

trx_undo_header_create(): Emit lower-level records instead of
writing MLOG_UNDO_HDR_CREATE records.

MariaDB stopped writing the record MLOG_UNDO_ERASE_END
in commit 0fd3def2 (10.3.3).
Merge trx_undo_erase_page_end() with its callers.

trx_undo_page_init(): Write lower-level redo log records by
invoking mtr_t::write().

page_zip_compress_write_log_no_data(): Remove.
We no longer write the MLOG_ZIP_PAGE_COMPRESS_NO_DATA record.
Instead, we will write MLOG_ZIP_PAGE_COMPRESS records.

No longer emit the redo log records
MLOG_LIST_END_COPY_CREATED, MLOG_COMP_LIST_END_COPY_CREATED.

size_t compared to int

Remove deprecated system variable multi_range_count. It was ignored from 5.3.

Variable is marked as deprecated since 10.1.6. Update tests to not make
use of it.

Remove the option from mysqld --help text.

thread_concurrency was ignored since 5.5. Remove it.

It was deprecated in 5.5 but it never issued a deprecation warning.
Make it issue a warning in 10.5.1.

REMOVED OPTIONS / SYSTEM VARIABLES
  * mysqld removed options will not stop the server from starting. They
    will be silently accepted, as if --loose flag is set. Removed options
    prefixes will not interfere with existing options prefixes. They are
    consumed last.
  * mysqld removed options will not show in --help.
  * mysqld system variables will be removed according to the deprecation
    & removal timeline and not function within the client interface once
    removed.

DEPRECTATED OPTIONS / SYSTEM VARIABLES
  * mysqld deprecated options will issue a warning to the user.
  * mysqld deprecated options will still be visible in --help.
  * mysqld system variables will be removed in the next GA version that is
    past EOL of the version that deprecated the variable.
  * deprecated options / variables will not be used anywhere in the server
    code the moment they are deprecated. At most, they will act as aliases.

The advantage of this policy is that it ensures upgrades will always
allow the user to start the server, even when upgrading from a very old
version. It is still possible for user applications to break when
upgrading, as system variables set via the client interface will return
errors. However, this will happen after a long time, with lots of
warnings between versions. The expected timeline is ~ 5 years until a
deprecated variable dissapears from the server.

Remove usage of deprecated variable storage_engine. It was deprecated in 5.5 but
it never issued a deprecation warning. Make it issue a warning in 10.5.1.

Replaced with default_storage_engine.

For compatibility with diagnostic software, let us
return a dummy buffer pool identifier 0 and restore
the columns that were initially deleted in
commit 1a6f708e:

	information_schema.innodb_buffer_page.pool_id
	information_schema.innodb_buffer_page_lru.pool_id
	information_schema.innodb_buffer_pool_stats.pool_id
	information_schema.innodb_cmpmem.buffer_pool_instance
	information_schema.innodb_cmpmem_reset.buffer_pool_instance

Thanks to Vladislav Vaintroub for pointing this out.

Allocation should use ALIGN_SIZE when we need to make sure that we
have atleast enough space to store one record in MERGEBUFF2 buffers

Our benchmarking efforts indicate that the reasons for splitting the
buf_pool in commit c18084f7
have mostly gone away, possibly as a result of
mysql/mysql-server@ce6109ebfdedfdf185e391a0c97dc6d33867ed78
or similar work.

Only in one write-heavy benchmark where the working set size is
ten times the buffer pool size, the buf_pool->mutex would be
less contended with 4 buffer pool instances than with 1 instance,
in buf_page_io_complete(). That contention could be alleviated
further by making more use of std::atomic and by splitting
buf_pool_t::mutex further (MDEV-15053).

We will deprecate and ignore the following parameters:

	innodb_buffer_pool_instances
	innodb_page_cleaners

There will be only one buffer pool and one page cleaner task.

In a number of INFORMATION_SCHEMA views, columns that indicated
the buffer pool instance will be removed:

	information_schema.innodb_buffer_page.pool_id
	information_schema.innodb_buffer_page_lru.pool_id
	information_schema.innodb_buffer_pool_stats.pool_id
	information_schema.innodb_cmpmem.buffer_pool_instance
	information_schema.innodb_cmpmem_reset.buffer_pool_instance

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.