buf_pool_t::create(), buf_pool_t::chunk_t::create(): Only initialize
the first page descriptor of each chunk.

buf_pool_t::lazy_allocate(): Lazily initialize a previously allocated
page descriptor and advance buf_pool_t::chunk_t::blocks_end until
the allocated capacity has been reached (blocks_end == blocks + size).

buf_pool_t::lazy_allocate_size(): Return the number of allocation requests
that buf_pool_t::lazy_allocate() can serve.

buf_pool_t::fully_initialized: Set if lazy_allocate_size() == 0.

Most references to chunk->size have been replaced with
chunk->blocks_end - chunk->blocks.

trx_t::commit_in_memory(): Set commit_lsn=0 if the log was written.

trx_commit_complete_for_mysql(): Remove some conditions.
We will rely on trx->commit_lsn.

innobase_commit_ordered_2(): Simplify some conditions.
A read-write transaction will always carry nonzero trx_t::id.
Let us unconditionally reset mysql_log_file_name, flush_log_later
after trx_t::commit() was invoked.

trx_t::commit_empty(): Ensure that the system-wide transaction identifier
will be persisted up to this->id, so that there will not be warnings or
errors due to a PAGE_MAX_TRX_ID being too large. We might have modified
that on secondary index pages before being rolled back, and those changes
are never rolled back.

trx_t::commit_empty(): A special case of transaction "commit" when
the transaction was actually rolled back or the persistent undo log
is empty. In this case, we need to change the undo log header state to
TRX_UNDO_CACHED and move the undo log from rseg->undo_list to
rseg->undo_cached for fast reuse. Furthermore, unless this is the only
undo log record in the page, we will remove the record and rewind
TRX_UNDO_PAGE_START, TRX_UNDO_PAGE_FREE, TRX_UNDO_LAST_LOG.

Even though it is not going to be written persistently anywhere,
we will invoke trx_sys.assign_new_trx_no(this), so that in the test
innodb.instant_alter everything will be purged as expected.

trx_t::write_serialisation_history(): Renamed from
trx_write_serialisation_history(). If there is no undo log,
invoke commit_empty().

trx_purge_add_undo_to_history(): Simplify an assertion and remove a
comment. This function will not be invoked on an empty undo log
anymore.

trx_undo_header_create(): Add a debug assertion.

trx_undo_mem_create_at_db_start(): Remove a duplicated assignment.

trx_commit_complete_for_mysql(): Remove some conditions.
We will rely on trx_flush_log_if_needed().

trx_t::must_flush_log_later: Remove. trx_commit_complete_for_mysql()
can simply check for trx_t::flush_log_later.

trx_t::commit_in_memory(): Treat flush_log_later as input and output.

trx_flush_log_if_needed_low(): Renamed to trx_flush_log_if_needed().
Assert that innodb_flush_log_at_trx_commit!=0 was checked by
the caller and that the transaction is not in XA PREPARE state.

trx_write_serialisation_history(): Move some code from
trx_purge_add_undo_to_history().

trx_prepare(): Invoke log_write_up_to() directly if needed.

innobase_commit_ordered_2(): Remove a condition, and do not reset
trx_t::flush_log_later, because it must be passed from
trx_t::commit_in_memory() to trx_commit_complete_for_mysql().

trx_commit_cleanup(): Clean up any temporary undo log.
Replaces trx_undo_commit_cleanup() and trx_undo_seg_free().

trx_write_serialisation_history(): Commit the mini-transaction.
Do not touch temporary undo logs. Assume that a persistent rollback
segment has been assigned.

trx_serialise(): Merged into trx_write_serialisation_history().

trx_t::commit_low(): Correct some comments and assertions.

trx_t::commit_persist(): Only invoke commit_low() on a mini-transaction
if the persistent state needs to change.

MDEV-31737 : Node never returns from Donor/Desynced to Synced when wsrep_mode = BF_ABORT_MARIABACKUP

Problem was incorrect condition when node should have
resumed and resync at backup_end. Simplified condition
to fix the problem and added missing test case for
this wsrep_mode = BF_ABORT_MARIABACKUP.
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>

- InnoDB aborts when table is dropping the column. This is
caused by 5f09b53b (MDEV-31086).
While iterating the altered table fields, we fail to consider
the dropped columns.

when validating vcol's (default, check, etc) in ALTER TABLE
vcol_info->flags are modified in place. This means that if ALTER TABLE
fails for any reason we need to restore them to their original values.

(mroonga was freeing the memory on ::reset() but not on ::close())

MDEV-31743 Server crash in store_length, assertion failure in Type_handler_string_result::sort_length

After MDEV-21580 the truncation of SORT_FIELD::length
  set_if_smaller(sortorder->length, thd->variables.max_sort_length)

became conditional:
  if (is_variable_sized())
    set_if_smaller(length, thd->variables.max_sort_length)

To provide correct functioning of is_variable_sized() SORT_FIELD::type
must be set properly. This commit adds the necessary initialization
of SORT_FIELD::type to JOIN_TAB::remove_duplicates() as it is done
in filesort's sortlength() function.

DBUG_ASSERT is added to sortlength() just in case to prevent
a possible uint32 overflow

MDEV-31822 ALTER TABLE ENGINE=x started failing instead of producing warning on unsupported TRANSACTIONAL=1

make TRANSACTIONAL table option behave similar to other engine-defined
table options. If the engine doesn't suport it:
* if specified expicitly in CREATE or ALTER - it's ER_UNKNOWN_OPTION
* an error or a warning depending on sql_mode IGNORE_BAD_TABLE_OPTIONS
* in ALTER TABLE from the engine that suppors it to the engine that
  doesn't - silently preserved (no warning)
* it is commented out in SHOW CREATE unless IGNORE_BAD_TABLE_OPTIONS

* invoke check_expression() for all vcol_info's in
  mysql_prepare_create_table() to check for FK CASCADE
* also check for SET NULL and SET DEFAULT
* to check against existing FKs when a vcol is added in ALTER TABLE,
  old FKs must be added to the new_key_list just like other indexes are
* check columns recursively, if vcol1 references vcol2,
  flags of vcol2 must be taken into account
* remove check_table_name_processor(), put that logic under
  check_vcol_func_processor() to avoid walking the tree twice

mark old keys in the ALTER TABLE with the `old` flag, not with
the `key_create_info.check_for_duplicate_indexes`.

This allows to mark old foreign keys too.

to declutter Item_field::check_vcol_func_processor(), move alter_info
specific part of it into Alter_info::check_vcol_field()

also, prefer Lex_table_name and Lex_ident over LEX_CSTRING

HA_UNIQUE_CHECK was
* only used internally by MyISAM/Aria
* only used for internal temporary tables (for DISTINCT)
* never saved in frm
* saved in MYI/MAD but only for temporary tables
* only set, never checked

it's safe to remove it and free the bit (there are only 16 of them)

Do not attempt to produce "r_engine_stats" on the temporary (=work) tables.
These tables may be
- re-created during the query execution
- freed during the query execution (This is done e.g. in JOIN::cleanup(),
  before we produce ANALYZE FORMAT=JSON output).

- (Also, make save_explain_data() functions not set handler_for_stats
  to point to handler objects that do not have handler->handler_stats set.
  If the storage engine is not collecting handler_stats, it will not have
  them when we're producing ANALYZE FORMAT=JSON output, either).

buf_page_t::write_complete(), buf_page_write_complete(),
IORequest::write_complete(): Add a parameter for passing
an error code. If an error occurred, we will release the
io-fix, buffer-fix and page latch but not reset the
oldest_modification field. The block would remain in
buf_pool.LRU and possibly buf_pool.flush_list, to be written
again later, by buf_flush_page_cleaner(). If all page writes
start consistently failing, all write threads should eventually
hang in log_free_check() because the log checkpoint cannot
be advanced to make room in the circular write-ahead-log ib_logfile0.

IORequest::read_complete(): Add a parameter for passing
an error code. If a read operation fails, we report the error
and discard the page, just like we would do if the page checksum
was not validated or the page could not be decrypted.
This only affects asynchronous reads, due to linear or random read-ahead
or crash recovery. When buf_page_get_low() invokes buf_read_page(),
that will be a synchronous read, not involving this code.

This was tested by randomly injecting errors in
write_io_callback() and read_io_callback(), like this:

  if (!ut_rnd_interval(100))
    cb->m_err= 42;

buf_LRU_free_page(): The block may also be in the IBUF_EXIST state
when executing the test innodb.innodb_bulk_create_index_debug.

buf_LRU_free_page(): When we are discarding the uncompressed copy of a
ROW_FORMAT=COMPRESSED page, buf_page_t::can_relocate() must have ensured
that the block descriptor state is one of FREED, UNFIXED, REINIT.
Do not overwrite the state with UNFIXED. We do not want to write back
pages that were actually freed, and we want to avoid doublewrite for
pages that were (re)initialized by log records written since the latest
checkpoint. Last but not least, we do not want crashes like those that
commit dc1bd180 (MDEV-31386)
was supposed to fix.

The test innodb_zip.wl5522_zip should typically cover all 3 states.

This bug is a regression due to
commit aaef2e1d (MDEV-27058).

failed SHOW CREATE FUNCTION means we don't dump this function,
but should still try to dump all other functions

don't construct open ranges from prefix blob keys for < (less than)
just as it's already done for > (greater than)

because prefix KEY_PART doesn't create prefix Field for blobs
(see open_table_from_share() near "Create a new field for the key part"),
so stored_field_cmp_to_item() will compare the original field to the
value not taking the prefix length into account.

This reverts commit add0c01b

Duplicates must be avoided in FTS_DOC_ID_INDEX