In commit ea37b144
we removed the MDEV-16222 test case but forgot to remove
the debug instrumentation.

ibuf_read_merge_pages(): Request a possibly freed page.
The change buffer is discarded lazily for freed pages either
by this function or when buf_page_create() reuses a page.

buf_page_get_low(): Relax a debug assertion.
Do not attempt change buffer merge on freed pages.

ibuf_merge_or_delete_for_page(): Assert that the page state is NORMAL.
INIT_ON_FLUSH is not possible, because in that case buf_page_create()
should have removed any buffered changes for the page.

buf_page_get_gen(): Apply buffered changes also in the case when
we can avoid reading the page based on buffered redo log records.
This addresses a hard-to-reproduce scenario that was broken in
commit 6697135c.

Let us use the common accessor function fil_page_get_type()
instead of accessing the page header field FIL_PAGE_TYPE directly.

fsp0pagecompress.h: Remove.
Invoke fil_page_get_type() and FSP_FLAGS_GET_PAGE_COMPRESSION_LEVEL
directly.

log_block_get_flush_bit(), log_block_set_flush_bit():
Access the byte directly.

dict_sys_read_row_id(): Remove (unused function).

Part of
MDEV-18353 - Shutdown may miss to wait for connection thread

MDEV-22130 SHOW WARNINGS will SIGSEGV 10.5 optimized build after setting CHARACTER_SET_RESULTS to NULL and running any invalid SQL | Binary_string::copy_printable_hhhh

The old code did not take into account that
thd->variables.character_set_results can be NULL.

MDEV-22424 Server crashes in handler::check_duplicate_long_entry_key or Assertion `inited == NONE || lookup_handler != this' failed upon DELETE FOR PORTION on table with long unique key

even if we're *allowed to* convert DELETE .. FOR PERIOD OF
into an update internally, doesn't think we'll *be able to*.

We always have to prepare for insert.

MDEV-22185 Failing assertion: node->pcur->rel_pos == BTR_PCUR_ON or ER_KEY_NOT_FOUND or Assertion `inited==NONE' failed in handler::ha_index_init

long unique checks should be done for a partitioned table as a whole,
not for individual partitions.

Followup for f3f31eaa that extends it to UPDATE

as mentioned in f9f33b85 and generally to make it
easier to talk about

ha_innobase::check_if_supported_inplace_alter(): Do not allow
ALGORITHM=INSTANT for operations that avoid a table rebuild
but involve dropping (or creating) secondary indexes.

Now all access goes through _current_thd() and set_current_thd()
functions.

Some functions like THD::store_globals() can not fail now.

MDEV-20502 Queries against spider tables return wrong values for columns following constant declarations.

Add test cases.

MDEV-20502 Queries against spider tables return wrong values for columns following constant declarations.

Add test cases.

Do not show exact value as it depends order of test execution.
Instead use # for correct values and ERROR for incorrect.

fil_flush_file_spaces(): Remove the constant parameter.

buf_flush_start(), buf_flush_end(): Use static linkage.

fil_page_get_prev(), fil_page_get_next(), fil_addr_is_null(): Remove.

commit 5e7e7153 accidentally
broke the build without WSREP, by misplacing an #endif.

commit d467bb7e accidentally
broke the build without WSREP, by misplacing an #endif.

This is a partial backport of
commit 5e7e7153 from 10.4.

assert_trx_is_free(): Assert !is_wsrep().

trx_init(): Do not initialize trx->wsrep, because it must have been
initialized already.

trx_commit_in_memory(): Invoke wsrep_commit_ordered(). This call
was being skipped, because the transaction object had already been
freed to the pool.

trx_rollback_for_mysql(), innobase_commit_low(),
innobase_rollback_trx(): Always reset trx->wsrep.

This is a follow-up fix to the changes that were made in MDEV-7962.

assert_trx_is_free(): Assert !is_wsrep().

trx_init(): Do not initialize trx->wsrep, because it must have been
initialized already.

trx_t::commit_in_memory(): Invoke wsrep_commit_ordered(). This call
was being skipped, because the transaction object had already been
freed to the pool.

trx_rollback_for_mysql(), innobase_commit_low(),
innobase_close_connection(): Always reset trx->wsrep.

- InnoDB gives "table is marked as crashed and should be repaired" when
table schema mismatch.

Disable IPO (interprocedural optimization, aka /GL) on Windows
on libraries, from which server.dll exports symbols -  exporting symbols
does not work for objects compiled with /GL.

- Instant alter should change the metadata alone when table is
discarded. It shouldn't try to add metadata record in clustered index.
Also make the clustered index to non-instant format.

		FOREIGN_KEY_CHECKS is disabled

- Referenced index can be null While renaming the referenced column name.
In that case, rename the referenced column name in dict_foreign_t and
find the equivalent referenced index.

Variable was not updated after initialization.

- ALTER_ALGORITHM should be substituted when there is no mention of
algorithm in alter statement.
- Introduced algorithm(thd) in Alter_info. It returns the
user requested algorithm. If user doesn't specify algorithm explicitly then
it returns alter_algorithm variable.
- changed algorithm() to get_algorithm(thd) to return algorithm name for
displaying the error.
- set_requested_algorithm(algo_value) to avoid direct assignment on
requested_algorithm variable.
- Avoid direct access of requested_algorithm to encapsulate
requested_algorithm variable