The problems were in the code of sql_show.cc. There the tables
could be opened in such a way that mysql_derived_init() never
worked for CTE tables. As a result they were not marked as
derived and mysql_handle_derived() were not called for derived
tables used in their specifications.

The "is null" function performs one operation which no other Item_func
does, which is to update used tables during fix_length_and_dec().

This however can not be performed before window functions have had a
chance to resolve their order by and partition by definitions, which
happens after the initial setup_fields call. Consequently, do not call
Item_func_isnull update_used_tables during fix_length_and_dec().

There was another issue detected once the crash was resolved.
Because window functions did not implement is_null() method, we would
end up returning bad results for "is null" and "is not null" functions.
Implemented is_null() method for Item_windowfunc.

During statement preparation st_order::item gets set to a value in
ref_ptr_array. During statement execution we were overriding that value,
causing subsequent checks for window functions to return true.

Whenever we do any setting from ref_ptr_array, make sure to always
store the value in all_fields as well.

For function items containing window functions, as MDEV-12336 has
discovered, we don't need to create a separate Item_direct_ref or
Item_aggregate_ref as they will be computed directly from the top-level
item once the window function argument columns are computed.

These self references were previously used to avoid having to check the
IO_CACHE's type. However, a benchmark shows that on x86 5930k stock,
the type comparison is marginally faster than the double pointer dereference.
For 40 billion my_b_tell calls, the difference is .1 seconds in favor of performing the
type check. (Basically there is no measurable difference)

To prevent bugs from copying the structure using the equals(=) operator,
and having to do the bookkeeping manually, remove these "convenience"
variables.

srv_log_files_created: A debug flag to ensure that InnoDB redo log
files can only be created once in the server lifetime, and that
after log files have been created, no crash recovery will take place.

recv_scan_log_recs(): Detect the special case where the log consists
of a sole MLOG_CHECKPOINT record, such as immediately after creating
the redo logs.

recv_recovery_from_checkpoint_start(): Skip the recovery message
if the redo log is logically empty.

A merge error caused InnoDB bootstrap to fail when
innodb_undo_tablespaces was set to more than 2.
This was because of a bug that was introduced to
srv_undo_tablespaces_init() by the merge.

Furthermore, some adjustments for Oracle Bug#25551311 aka
Bug#23517560 changes were forgotten. We must minimize direct
references to srv_undo_tablespaces_open and use predicates
instead.

srv_undo_tablespaces_init(): Increment srv_undo_tablespaces_open
once, not twice, per loop iteration.

is_system_or_undo_tablespace(): Remove (unused function).

is_predefined_tablespace(): Invoke srv_is_undo_tablespace().

When it comes to DEFAULT values of columns, InnoDB is imposing both
unnecessary and insufficient conditions on whether ALGORITHM=INPLACE
should be allowed for ALTER TABLE.

When changing an existing column to NOT NULL, any NULL values in the
columns only get a special treatment if the column is changed to an
AUTO_INCREMENT column (which is not supported by ALGORITHM=INPLACE)
or the column type is TIMESTAMP. In all other cases, an error
must be reported for the failure to convert a NULL value to NOT NULL.

InnoDB was unnecessarily interested in whether the DEFAULT value
is not constant when altering other than TIMESTAMP columns. Also,
when changing a TIMESTAMP column to NOT NULL, InnoDB was performing
an insufficient check, and it was incorrectly allowing a constant
DEFAULT value while not being able to replace NULL values with that
constant value.

Furthermore, in ADD COLUMN, InnoDB is unnecessarily rejecting certain
nondeterministic DEFAULT expressions (depending on the session
parameters or the current time).

This patch corrects the fix for mdev-12845.

Merged relevant part of MySQL revision:
https://github.com/mysql/mysql-server/commit/565d20b44f24fcc855dc616164d87b03cfad10bc

Relaxed assertion (in MySQL it was removed).
For "LOCK TABLES t1 WRITE CONCURRENT, t1 READ" upgrade lock to weakest
existing suitable lock, which is MDL_SHARED_NO_READ_WRITE.

buf_flush_page_cleaner_coordinator(): Signal the thread creator
that the error log output regarding setpriority() has been issued.

innobase_start_or_create_for_mysql(): Wait for
buf_flush_page_cleaner_coordinator() to completely start up.

This prevents sporadic failures of tests that search the server
error log for InnoDB redo log recovery messages.

While the primary purpose of innodb_force_recovery is to allow
data to be rescued from an InnoDB instance that would crash due
to some data corruption, the settings 1, 2, or 3 are relatively
safe to use and there is no need to prevent write transactions
in these modes.

The setting innodb_force_recovery=4 and above can cause database
corruption. For those modes, we already set the flag
high_level_read_only to disable modifications, except DROP TABLE.

MODIFICATIONS_NOT_ALLOWED_MSG_FORCE_RECOVERY: Remove. There is no
need to spam the error log for each refused DML operation. It suffices
to return an error to the client. There will be messages at startup
if innodb_read_only or innodb_force_recovery are preventing writes.

This patch fills in a serious flaw in the
code that supports condition pushdown into
materialized views / derived tables.

If a predicate happened to contain a reference
to a mergeable view / derived table and it does
not depended directly on the target materialized
view / derived table then the predicate was not
considered as a subject to pusdown to this view
/ derived table.

If no checkpoint information is present, do not write to the data files.
These writes would violate innodb_read_only=ON, among other things.

The original intention of the setting innodb_force_recovery=3 was to
disable background activity that could create trouble, most notably,
the rollback of incomplete transactions, and the purge of transaction
history.

MySQL 5.6 introduced more background threads, it is creating
dict_stats_thread and fts_optimize_thread even though these threads
are at least as non-essential as the rollback and purge. These
threads are in fact worse, because they can create new transactions
on their own.

innobase_start_or_create_for_mysql(): Do not create any internal
undo log sources unless innodb_force_recovery<3.

Parameters can be MYSQL_TYPE_VARCHAR for long data load.

These errors should only be possible when bootstrap is aborted
and restarted.

buf_flush_init_for_writing(): Reset the FIL_PAGE_TYPE
of the TRX_SYS page to the canonical value
FIL_PAGE_TYPE_TRX_SYS instead of FIL_PAGE_TYPE_UNKNOWN.

When running setup fields during the final step of insert using select
the final setup_fields does not have any sum functions. Our current
condition for calling split_sum_func however would attempt to use an empty
NULL sum_func_list, if the item contained a window function.

The solution is to not perform another split_sum_func for the item
containing a window function if we do not actually have a sum_func_list.

This will also change the minimum and maximum value of
innodb_log_file_size to 1MiB and 512GiB, respectively.

MDEV-12975 InnoDB redo log minimum size check uses detected file size instead of requested innodb_log_file_size

log_calc_max_ages(): Use the requested size in the check, instead of
the detected redo log size. The redo log will be resized at startup
if it differs from what has been requested.

The option was basically duplicating InnoDB functionality.
Persistent statistics can be accessed via the tables
mysql.innodb_table_stats and mysql.innodb_index_stats.

These functions cannot possibly work in MariaDB 10.2, and it is
uncertain if they really work in 10.1 either.

This is another attempt to fix the bug mdev-12992.
This patch introduces st_select_lex::context_analysis_place for
the place in SELECT where context analysis is currently performed.
It's similar to st_select_lex::parsing_place, but it is used at
the preparation stage.

             lock not released after timeout

Release GRL if FLUSH TABLES phase failed.

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.

The sole purpose of handlerton::release_temporary_latches and its wrapper
function was to release the InnoDB adaptive hash index latch
(btr_search_latch).

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. As part of that,
the function trx_search_latch_release_if_reserved() was changed to an
assertion and the function trx_reserve_search_latch_if_not_reserved()
was removed, and handlerton::release_temporary_latches() practically
became a no-op.

Note: MDEV-12121 replaced the function
trx_search_latch_release_if_reserved()
with the more appropriately named macro trx_assert_no_search_latch().

dict_sys_tables_type_to_tf(): Change the parameter n_cols to not_redundant.

dict_tf_is_valid_not_redundant(): Refactored from dict_tf_is_valid().

dict_sys_tables_type_valid(): Replaces dict_sys_tables_type_validate().
Use the common function dict_tf_is_valid_not_redundant(), which validates
PAGE_COMPRESSION_LEVEL more strictly.

DICT_TF_GET_UNUSED(flags): Remove.

innodb.table_flags: Adjust the test case. Due to the MDEV-12873 fix
in 10.2, the corrupted flags for table test.td would be converted,
and a tablespace flag mismatch will occur when trying to open the file.

MDEV-12873 InnoDB SYS_TABLES.TYPE incompatibility for PAGE_COMPRESSED=YES in MariaDB 10.2.2 to 10.2.6

Remove the SHARED_SPACE flag that was erroneously introduced in
MariaDB 10.2.2, and shift the SYS_TABLES.TYPE flags back to where
they were before MariaDB 10.2.2. While doing this, ensure that
tables created with affected MariaDB versions can be loaded,
and also ensure that tables created with MySQL 5.7 using the
TABLESPACE attribute cannot be loaded.

MariaDB 10.2.2 picked the SHARED_SPACE flag from MySQL 5.7,
shifting the MariaDB 10.1 flags PAGE_COMPRESSION, PAGE_COMPRESSION_LEVEL,
ATOMIC_WRITES by one bit. The SHARED_SPACE flag would always
be written as 0 by MariaDB, because MariaDB does not support
CREATE TABLESPACE or CREATE TABLE...TABLESPACE for InnoDB.

So, instead of the bits AALLLLCxxxxxxx we would have
AALLLLC0xxxxxxx if the table was created with MariaDB 10.2.2
to 10.2.6. (AA=ATOMIC_WRITES, LLLL=PAGE_COMPRESSION_LEVEL,
C=PAGE_COMPRESSED, xxxxxxx=7 bits that were not moved.)

PAGE_COMPRESSED=NO implies LLLLC=00000. That is not a problem.

If someone created a table in MariaDB 10.2.2 or 10.2.3 with
the attribute ATOMIC_WRITES=OFF (value 2; AA=10) and without
PAGE_COMPRESSED=YES or PAGE_COMPRESSION_LEVEL, the table should be
rejected. We ignore this problem, because it should be unlikely
for anyone to specify ATOMIC_WRITES=OFF, and because 10.2.2 and
10.2.2 were not mature releases. The value ATOMIC_WRITES=ON (1)
would be interpreted as ATOMIC_WRITES=OFF, but starting with
MariaDB 10.2.4 the ATOMIC_WRITES attribute is ignored.

PAGE_COMPRESSED=YES implies that PAGE_COMPRESSION_LEVEL be between
1 and 9 and that ROW_FORMAT be COMPACT or DYNAMIC. Thus, the affected
wrong bit pattern in SYS_TABLES.TYPE is of the form AALLLL10DB00001
where D signals the presence of a DATA DIRECTORY attribute and B is 1
for ROW_FORMAT=DYNAMIC and 0 for ROW_FORMAT=COMPACT. We must interpret
this bit pattern as AALLLL1DB00001 (discarding the extraneous 0 bit).

dict_sys_tables_rec_read(): Adjust the affected bit pattern when
reading the SYS_TABLES.TYPE column. In case of invalid flags,
report both SYS_TABLES.TYPE (after possible adjustment) and
SYS_TABLES.MIX_LEN.

dict_load_table_one(): Replace an unreachable condition on
!dict_tf2_is_valid() with a debug assertion. The flags will already
have been validated by dict_sys_tables_rec_read(); if that validation
fails, dict_load_table_low() will have failed.

fil_ibd_create(): Shorten an error message about a file pre-existing.

Datafile::validate_to_dd(): Clarify an error message about tablespace
flags mismatch.

ha_innobase::open(): Remove an unnecessary warning message.

dict_tf_is_valid(): Simplify and stricten the logic. Validate the
values of PAGE_COMPRESSION. Remove error log output; let the callers
handle that.

DICT_TF_BITS: Remove ATOMIC_WRITES, PAGE_ENCRYPTION, PAGE_ENCRYPTION_KEY.
The ATOMIC_WRITES is ignored once the SYS_TABLES.TYPE has been validated;
there is no need to store it in dict_table_t::flags. The PAGE_ENCRYPTION
and PAGE_ENCRYPTION_KEY are unused since MariaDB 10.1.4 (the GA release
was 10.1.8).

DICT_TF_BIT_MASK: Remove (unused).

FSP_FLAGS_MEM_ATOMIC_WRITES: Remove (the flags are never read).

row_import_read_v1(): Display an error if dict_tf_is_valid() fails.

dict_table_t::thd: Remove. This was only used by btr_root_block_get()
for reporting decryption failures, and it was only assigned by
ha_innobase::open(), and never cleared. This could mean that if a
connection is closed, the pointer would become stale, and the server
could crash while trying to report the error. It could also mean
that an error is being reported to the wrong client. It is better
to use current_thd in this case, even though it could mean that if
the code is invoked from an InnoDB background operation, there would
be no connection to which to send the error message.

Remove dict_table_t::crypt_data and dict_table_t::page_0_read.
These fields were never read.

fil_open_single_table_tablespace(): Remove the parameter "table".