The page allocation bitmaps in the extent descriptor pages
contain two bits per page: XDES_FREE_BIT and XDES_CLEAN_BIT,
which is unused. Simplify read access.

xdes_is_free(descr,mtr): Remove. Use !xdes_get_n_used(descr) instead.

xdes_is_free(): Replaces xdes_get_bit(), xdes_mtr_get_bit().

xdes_find_free(): Replaces xdes_find_bit().

fsp_seg_inode_page_get_nth_inode(): Remove the redundant parameters
physical_size, mtr.

fsp_seg_inode_page_find_used(), fsp_seg_inode_page_find_free():
Remove the redundant parameter mtr.

Since commit 5d596064
fil_page_type_is_index() expects uint16_t, not ulint.

fsp_alloc_seg_inode_page(): Ever since
commit 3926673c
all newly allocated pages are zero-initialized.
Assert that this is the case for the FSEG_ID fields.
(Side note: before that fix, other parts of the pages
could contain nonzero garbage.)

btr_store_big_rec_extern_fields(): Remove the redundant initialization
of the most significant 32 bits of BTR_EXTERN_LEN. InnoDB never supported
BLOBs that are longer than 4GiB. In fact, dtuple_convert_big_rec()
would write emit an error message if a clustered index record tuple would
exceed 1,000,000,000 bytes in length.

PageConverter::update_index_page(): Invoke lower-level writes directly.

The function mach_read_ulint() is a wrapper for the lower-level
functions mach_read_from_1(), mach_read_from_2(), mach_read_from_8().
Invoke those functions directly, for better readability of the code.

mtr_t::read_ulint(), mtr_read_ulint(): Remove. Yes, we will lose the
ability to assert that the read is covered by the mini-transaction.
We would still check that on writes, and any writes that
wrongly bypass mini-transaction logging would likely be caught by
stress testing with Mariabackup.

Always use the MLOG_MEMSET record for writing FIL_NULL,
because it is more compact.

MDEV-17553 Enable setting start datetime for interval partitioned history of system versioned tables

* Explicit STARTS syntax
* SHOW CREATE
* Default STARTS rounding depending on INTERVAL type
* Warn when STARTS timestamp is later than query time
* Fix uninitialized Lex->create_last_non_select_table under
  mysql_unpack_partition()

Default STARTS rounding depending on INTERVAL type

If STARTS clause is omitted, default one is assigned with value
derived from query timestamp. The rounding is done on STARTS value
depending on INTERVAL type:

SECOND: no rounding is done;
MINUTE: timestamp seconds is set to 0;
HOUR: timestamp seconds and minutes are set to 0;
DAY, WEEK, MONTH and YEAR: timestamp seconds, minutes and hours are
set to 0 (the date of rotation is kept as current date).

A conflict between MDEV-19514 (b42294bc)
and MDEV-20934 (d7a24017)
was resolved. We will not invoke the function ibuf_delete_recs()
from ibuf_merge_or_delete_for_page(). Instead, we will add that
logic to the function ibuf_read_merge_pages().

Due to MDEV-12288, the slow shutdown in MariaDB 10.3 will include
resetting the DB_TRX_ID for all inserted records. This might
cause the 60-second shutdown_server timeout to be exceeded.
Let us wait for the purge to complete before initiating slow shutdown.

dict_index_add_to_cache(): Make the 'index' a reference to a pointer,
so that the caller will avoid the expensive call to
dict_index_get_if_in_cache_low().

Due to a data corruption bug that may have occurred a long time earlier
(possibly involving physical backup and MySQL Bug #69122, which was
addressed in commit f166ec71)
it seems possible that the InnoDB change buffer might end up containing
entries, while no buffered changes exist according to the change buffer
bitmap pages in the .ibd files.

ibuf_delete_recs(): New function, to be invoked on slow shutdown only.
Remove all buffered changes for a specific page.

ibuf_merge_or_delete_for_page(): If the change buffer bitmap is clean
and a slow shutdown is in progress, invoke ibuf_delete_recs().
We do not want to do that during normal operation, due to the additional
overhead that is involved. The bitmap page should be consistent with
the change buffer in the first place.

InnoDB: Assertion failure in file .../dict/dict0dict.cc line ...
InnoDB: Failing assertion: table->can_be_evicted

This fixes a regression that was caused by the fix of MDEV-20621
(commit a41d4297).
MySQL 5.6 (and MariaDB 10.0) introduced eviction of tables from
the InnoDB data dictionary cache. Tables that are connected to
FOREIGN KEY constraints or FULLTEXT INDEX are exempt of the eviction.
With the problematic change, a table that would already be exempt
from eviction due to FOREIGN KEY would cause the problem if there
also was a FULLTEXT INDEX defined on it.

dict_load_table(): Only prevent eviction if table->can_be_evicted holds.

MDEV-20985 Add LEX methods stmt_drop_{function|procedure}() and stmt_alter_{function|procedure}_start()

Adding a few helper LEX methods,
to unify sql_yacc.yy and sql_yacc_ora.yy easier

This is a logically better position.
Also, this makes the code in sql_yacc.yy and sql_yacc_ora.yy look more similar.

Do not rely on existence of CMakeFiles/${target}.dir directory existence
It is not there for custom targets in Ninja build.

Don't save/restore HP_INFO as it could be changed by a concurrent thread.
different parts of HP_INFO are protected by different mutexes and
the mutex that protect most of the HP_INFO does not protect its open_list
data.

As a bonus, make heap_check_heap() to take const HP_INFO* and not
make any changes there whatsoever.

Something was wrong with the removal of pointer indirection,
because on 32-bit Windows we got crash recovery failures.
Curiously, WITH_ASAN of a 32-bit debug build did not notice anything.

This reverts a part of commit b7fc2c89.

We have a 2MiB recv_sys.buf for the initial buffering. The minimum size
of log_sys.buf would be 16MiB, and that buffer should be practically
unused during recovery. If the buffer pool size is measured in gigabytes,
it would indeed make sense to use the buffer pool for the recovered log
records, perhaps after we have run out of log_sys.buf.

FIXME: allow the entire buf_block_t::frame to be used for buffered
log records, and remove MEM_HEAP_FOR_RECV_SYS. For example, use
buf_page_t::list or buf_page_t::LRU for keeping track of memory that
was allocated for recovery? Most members of buf_block_t
(except buf_block_t::frame) are unused when
block->page.state == BUF_BLOCK_MEMORY.

dict_table_rename_in_cache(): Use strcpy() instead of strncpy(),
because they are known to be equivalent in this case (the length
of old_name was already validated).

mariabackup: Invoke strncpy() with one less than the buffer size,
and explicitly add NUL as the last byte of the buffer.

Follow-up to commit 8965ae27:
always initialize found_group.

recv_t, recv_t::data_t: Define constructors that copy the log records

Ideally, we should remove recv_sys.buf, RECV_DATA_BLOCK_SIZE,
and recv_sys_justify_left_parsing_buf(), and let the
recv_sys.pages point directly to a buffer of parsed redo log
records.

The RECV_PARSING_BUF_SIZE (size of recv_sys.buf) is only 2MiB,
while the minimum innodb_log_buffer_size (size of log_sys.buf) is 16MiB,
and log_sys.buf is unused during redo log apply!

Except for fil_name_process(), which invokes os_normalize_path(),
the redo log record parser will not modify the redo log records.
Add const qualifiers accordingly.

followup to 00c3a288