The BtrBulk class, which was introduced in MySQL 5.7, is by design
the exclusive writer to an index. It is therefore unnecessary to
acquire the dict_index_t::lock in that code.

Holding the dict_index_t::lock would unnecessarily block other threads
(SQL connections and the InnoDB purge threads) from buffering concurrent
modifications to being-created secondary indexes.

This fix is motivated by a change in MySQL 5.7.28:
Bug #29008298 MYSQLD CRASHES ITSELF WHEN CREATING INDEX
mysql/mysql-server@f9fb96c20f9d190f654e7aa2387255bf80fd6e45

PageBulk::init(), PageBulk::latch(): Never acquire m_index->lock.

PageBulk::storeExt(): Remove some pointer indirection, and improve
a debug assertion that seems to prove that some code is redundant.

BtrBulk::pageCommit(): Assert that m_index->lock is not being held.

btr_blob_log_check_t: Do not acquire m_index->lock if
m_op == BTR_STORE_INSERT_BULK. Add UNIV_UNLIKELY hints around
that condition.

btr_store_big_rec_extern_fields(): Allow index->lock not to be held
while op == BTR_STORE_INSERT_BULK. Add UNIV_UNLIKELY hints around
that condition.

BtrBulk::finish(): On error, the B-tree can be corrupted. Only upon
successful completion, it makes sense to validate the index.

It's a micro optimization. On most platforms CPUs has instructions to
compare with 0 fast. DB_SUCCESS is the most popular outcome of functions
and this patch optimized code like (err == DB_SUCCESS)

BtrBulk::finish(): bogus assertion fixed

fil_node_t::read_page0(): corrected usage of os_file_read()

que_eval_sql(): bugus assertion removed. Apparently it checked that
the field was assigned after having been zero-initialized at
object creation.

It turns out that the return type of os_file_read_func() was changed
in mysql/mysql-server@98909cefbc37e54efc6452c7e95bccbf64ac9213 (MySQL 5.7)
from ibool to dberr_t. The reviewer (if there was any) failed to
point out that because of future merges, it could be a bad idea to
change the return type of a function without changing the function name.

This change was applied to MariaDB 10.2.2 in
commit 2e814d47 but the
MariaDB-specific code was not fully adjusted accordingly,
e.g. in fil_node_open_file(). Essentially, code like
!os_file_read(...) became dead code in MariaDB and later
in Mariabackup 10.2, and we could be dealing with an uninitialized
buffer after a failed page read.

btr_page_free(): Renamed from btr_page_free_low().
If scrubbing is enabled, zero out the page with proper redo logging.
Only pass ahi=true to fseg_free_page() if the page is actually indexed.

fil_space_t::modify_check(): Renamed from fsp_space_modify_check().

fsp_init_file_page(): Define inline.

The page_size argument to buf_page_get_gen() only matters when the
page is going to be loaded into the buffer pool. Allow callers to
pass a dummy parameter when using BUF_GET_IF_IN_POOL (which would
return NULL if the block is not in the buffer pool).

Closes #965

Introduce the configuration option innodb_log_optimize_ddl
for controlling whether native index creation or table-rebuild
in InnoDB should keep optimizing the redo log
(and writing MLOG_INDEX_LOAD records to ensure that
concurrent backup would fail).

By default, we have innodb_log_optimize_ddl=ON, that is,
the default behaviour that was introduced in MariaDB 10.2.2
(with the merge of InnoDB from MySQL 5.7) will be unchanged.

BtrBulk::m_trx: Replaces m_trx_id. We must be able to check for
KILL QUERY even if !m_flush_observer (innodb_log_optimize_ddl=OFF).

page_cur_insert_rec_write_log(): Declare globally, so that this
can be called from PageBulk::insert().

row_merge_insert_index_tuples(): Remove the unused parameter trx_id.

row_merge_build_indexes(): Enable or disable redo logging based on
the innodb_log_optimize_ddl parameter.

PageBulk::init(), PageBulk::insert(), PageBulk::finish(): Write
redo log records if needed. For ROW_FORMAT=COMPRESSED, redo log
will be written in PageBulk::compress() unless we called
m_mtr.set_log_mode(MTR_LOG_NO_REDO).

Native ALTER TABLE is never invoked on temporary tables.

btr_store_big_rec_extern_fields(): Remove the unused parameter 'upd'
that was added in https://github.com/mysql/mysql-server/commit/ce0a1e85e24e48b8171f767b44330d
and merged to MariaDB 10.2.2
in commit 2e814d47.

This should affect debug builds only. Debug builds will check that
the status bits of ROW_FORMAT!=REDUNDANT records match the is_leaf
parameter.

The only observable change to non-debug should be the addition of
the is_leaf parameter to the function rec_copy_prefix_to_dtuple(),
and the removal of some calls to update the adaptive hash index
(it is only built for the leaf pages).

This change should have been made in MySQL 5.0.3, instead of
introducing the status flags in the ROW_FORMAT=COMPACT record header.

When the btr_search_latch was split into an array of latches
in MySQL 5.7.8 as part of the Oracle Bug#20985298 fix, the "caching"
of the latch across storage engine API calls was removed, and
the field trx->has_search_latch would only be set during a short
time frame in the execution of row_search_mvcc(), which was
formerly called row_search_for_mysql().

This means that the column
INFORMATION_SCHEMA.INNODB_TRX.TRX_ADAPTIVE_HASH_LATCHED will always
report 0. That column cannot be removed in MariaDB 10.2, but it
can be removed in future releases.

trx_t::has_search_latch: Remove.

trx_assert_no_search_latch(): Remove.

row_sel_try_search_shortcut_for_mysql(): Remove a redundant condition
on trx->has_search_latch (it was always true).

sync_check_iterate(): Make the parameter const.

sync_check_functor_t: Make the operator() const, and remove result()
and the virtual destructor. There is no need to have mutable state
in the functors.

sync_checker<bool>: Replaces dict_sync_check and btrsea_sync_check.

sync_check: Replaces btrsea_sync_check.

dict_sync_check: Instantiated from sync_checker.

sync_allowed_latches: Use std::find() directly on the array.
Remove the std::vector.

TrxInInnoDB::enter(), TrxInInnoDB::exit(): Remove obviously redundant
debug assertions on trx->in_depth, and use equality comparison against 0
because it could be more efficient on some architectures.

Contains also:
       MDEV-10549 mysqld: sql/handler.cc:2692: int handler::ha_index_first(uchar*): Assertion `table_share->tmp_table != NO_TMP_TABLE || m_lock_type != 2' failed. (branch bb-10.2-jan)
       Unlike MySQL, InnoDB still uses THR_LOCK in MariaDB

       MDEV-10548 Some of the debug sync waits do not work with InnoDB 5.7 (branch bb-10.2-jan)
       enable tests that were fixed in MDEV-10549

       MDEV-10548 Some of the debug sync waits do not work with InnoDB 5.7 (branch bb-10.2-jan)
       fix main.innodb_mysql_sync - re-enable online alter for partitioned innodb tables

Contains also

MDEV-10547: Test multi_update_innodb fails with InnoDB 5.7

	The failure happened because 5.7 has changed the signature of
	the bool handler::primary_key_is_clustered() const
	virtual function ("const" was added). InnoDB was using the old
	signature which caused the function not to be used.

MDEV-10550: Parallel replication lock waits/deadlock handling does not work with InnoDB 5.7

	Fixed mutexing problem on lock_trx_handle_wait. Note that
	rpl_parallel and rpl_optimistic_parallel tests still
	fail.

MDEV-10156 : Group commit tests fail on 10.2 InnoDB (branch bb-10.2-jan)
  Reason: incorrect merge

MDEV-10550: Parallel replication can't sync with master in InnoDB 5.7 (branch bb-10.2-jan)
  Reason: incorrect merge