This is a merge from 10.2, but the 10.2 version of this will not
be pushed into 10.2 yet, because the 10.2 version would include
backports of MDEV-14717 and MDEV-14585, which would introduce
a crash recovery regression: Tables could be lost on
table-rebuilding DDL operations, such as ALTER TABLE,
OPTIMIZE TABLE or this new backup-friendly TRUNCATE TABLE.
The test innodb.truncate_crash occasionally loses the table due to
the following bug:

MDEV-17158 log_write_up_to() sometimes fails

A crash-downgrade of a RENAME (or TRUNCATE or table-rebuilding
ALTER TABLE or OPTIMIZE TABLE) operation to an earlier 10.2 version
would trigger a debug assertion failure during rollback,
in trx_roll_pop_top_rec_of_trx(). In a non-debug build, the
TRX_UNDO_RENAME_TABLE record would be misinterpreted as an
update_undo log record, and typically the file name would be
interpreted as DB_TRX_ID,DB_ROLL_PTR,PRIMARY KEY. If a matching
record would be found, row_undo_mod() would hit ut_error in
switch (node->rec_type). Typically, ut_a(table2 == NULL) would
fail when opening the table from SQL.

Because of this, we prevent a crash-downgrade to earlier MariaDB 10.2
versions by changing the InnoDB redo log format identifier to the
10.3 identifier, and by introducing a subformat identifier so that
10.2 can continue to refuse crash-downgrade from 10.3 or later.
After a clean shutdown, a downgrade to MariaDB 10.2.13 or later would
still be possible thanks to MDEV-14909. A downgrade to older 10.2
versions is only possible after removing the log files (not recommended).

LOG_HEADER_FORMAT_CURRENT: Change to 103 (originally the 10.3 format).

log_group_t: Add subformat. For 10.2, we will use subformat 1,
and will refuse crash recovery from any other subformat of the
10.3 format, that is, a genuine 10.3 redo log.

recv_find_max_checkpoint(): Allow startup after clean shutdown
from a future LOG_HEADER_FORMAT_10_4 (unencrypted only).
We cannot handle the encrypted 10.4 redo log block format,
which was introduced in MDEV-12041. Allow crash recovery from
the original 10.2 format as well as the new format.
In Mariabackup --backup, do not allow any startup from 10.3 or 10.4
redo logs.

recv_recovery_from_checkpoint_start(): Skip redo log apply for
clean 10.3 redo log, but not for the new 10.2 redo log
(10.3 format, subformat 1).

srv_prepare_to_delete_redo_log_files(): On format or subformat
mismatch, set srv_log_file_size = 0, so that we will display the
correct message.

innobase_start_or_create_for_mysql(): Check for format or subformat
mismatch.

xtrabackup_backup_func(): Remove debug assertions that were made
redundant by the code changes in recv_find_max_checkpoint().

This is a backport of the following commits:
commit b4165985
commit 69e88de0
commit 40f4525f
commit 656f66de

Now that MDEV-14717 made RENAME TABLE crash-safe within InnoDB,
it should be safe to drop the #sql- tables within InnoDB during
crash recovery. These tables can be one of two things:

(1) #sql-ib related to deferred DROP TABLE (follow-up to MDEV-13407)
or to table-rebuilding ALTER TABLE...ALGORITHM=INPLACE
(since MDEV-14378, only related to the intermediate copy of a table),

(2) #sql- related to the intermediate copy of a table during
ALTER TABLE...ALGORITHM=COPY

We will not drop tables whose name starts with #sql2, because
the server can be killed during an ALGORITHM=COPY operation at
a point where the original table was renamed to #sql2 but the
finished intermediate copy was not yet renamed from #sql-
to the original table name.

If an old version of MariaDB Server before 10.2.13 (MDEV-11415)
was killed while ALTER TABLE...ALGORITHM=COPY was in progress,
after recovery there could be undo log records for some records that were
inserted into an intermediate copy of the table. Due to these undo log
records, InnoDB would resurrect locks at recovery, and the intermediate
table would be locked while we are trying to drop it. This would cause
a call to row_rename_table_for_mysql(), either from
row_mysql_drop_garbage_tables() or from the rollback of a RENAME
operation that was part of the ALTER TABLE.

row_rename_table_for_mysql(): Do not attempt to parse FOREIGN KEY
constraints when renaming from #sql-something to #sql-something-else,
because it does not make any sense.

row_drop_table_for_mysql(): When deferring DROP TABLE due to locks,
do not rename the table if its name already starts with the #sql-
prefix, which is what row_mysql_drop_garbage_tables() uses.
Previously, the too strict prefix #sql-ib was used, and some
tables were renamed unnecessarily.

Follow-up to MDEV-13407 innodb.drop_table_background failed in buildbot with "Tablespace for table exists"

This is a backport of commit 88aff5f4.

The InnoDB background DROP TABLE queue is something that we should
really remove, but are unable to until we remove dict_operation_lock
so that DDL and DML operations can be combined in a single transaction.

Because the queue is not persistent, it is not crash-safe. We should
in some way ensure that the deferred-dropped tables will be dropped
after server restart.

The existence of two separate transactions complicates the error handling
of CREATE TABLE...SELECT. We should really not break locks in DROP TABLE.

Our solution to these problems is to rename the table to a temporary
name, and to drop such-named tables on InnoDB startup. Also, the
queue will use table IDs instead of names from now on.

check-testcase.test: Ignore #sql-ib*.ibd files, because tables may enter
the background DROP TABLE queue shortly before the test finishes.

innodb.drop_table_background: Test CREATE...SELECT and the creation of
tables whose file name starts with #sql-ib.

innodb.alter_crash: Adjust the recovery, now that the #sql-ib tables
will be dropped on InnoDB startup.

row_mysql_drop_garbage_tables(): New function, to drop all #sql-ib tables
on InnoDB startup.

row_drop_table_for_mysql_in_background(): Remove an unnecessary and
misplaced call to log_buffer_flush_to_disk(). (The call should have been
after the transaction commit. We do not care about flushing the redo log
here, because the table would be dropped again at server startup.)

Remove the entry from the list after the table no longer exists.

If server shutdown has been initiated, empty the list without actually
dropping any tables. They will be dropped again on startup.

row_drop_table_for_mysql(): Do not call lock_remove_all_on_table().
Instead, if locks exist, defer the DROP TABLE until they do not exist.
If the table name does not start with #sql-ib, rename it to that prefix
before adding it to the background DROP TABLE queue.

This is a backport of commit 07e9ff1f.

Allow DROP TABLE `#mysql50##sql-...._.` to drop tables that were
being rebuilt by ALGORITHM=INPLACE

NOTE: If the server is killed after the table-rebuilding ALGORITHM=INPLACE
commits inside InnoDB but before the .frm file has been replaced, then
the recovery will involve something else than DROP TABLE.

NOTE: If the server is killed in a true inplace ALTER TABLE commits
inside InnoDB but before the .frm file has been replaced, then we
are really out of luck. To properly handle that situation, we would
need a transactional mysql.ddl_fixup table that directs recovery to
rename or remove files.

prepare_inplace_alter_table_dict(): Use the altered_table->s->table_name
for generating the new_table_name.

table_name_t::part_suffix: The start of the partition name suffix.

table_name_t::dbend(): Return the end of the schema name.

table_name_t::dblen(): Return the length of the schema name, in bytes.

table_name_t::basename(): Return the name without the schema name.

table_name_t::part(): Return the partition name, or NULL if none.

row_drop_table_for_mysql(): Assert for #sql, not #sql-ib.

This is a backport of commit 0bc36758
and commit 9eb3fcc9.

InnoDB in MariaDB 10.2 appears to only write MLOG_FILE_RENAME2
redo log records during table-rebuilding ALGORITHM=INPLACE operations.
We must write the records for any .ibd file renames, so that the
operations are crash-safe.

If InnoDB is killed during a RENAME TABLE operation, it can happen that
the transaction for updating the data dictionary will be rolled back.
But, nothing will roll back the renaming of the .ibd file
(the MLOG_FILE_RENAME2 only guarantees roll-forward), or for that matter,
the renaming of the dict_table_t::name in the dict_sys cache. We introduce
the undo log record TRX_UNDO_RENAME_TABLE to fix this.

fil_space_for_table_exists_in_mem(): Remove the parameters
adjust_space, table_id and some code that was trying to work around
these deficiencies.

fil_name_write_rename(): Write a MLOG_FILE_RENAME2 record.

dict_table_rename_in_cache(): Invoke fil_name_write_rename().

trx_undo_rec_copy(): Set the first 2 bytes to the length of the
copied undo log record.

trx_undo_page_report_rename(), trx_undo_report_rename():
Write a TRX_UNDO_RENAME_TABLE record with the old table name.

row_rename_table_for_mysql(): Invoke trx_undo_report_rename()
before modifying any data dictionary tables.

row_undo_ins_parse_undo_rec(): Roll back TRX_UNDO_RENAME_TABLE
by invoking dict_table_rename_in_cache(), which will take care
of both renaming the table and the file.

ha_innobase::truncate(): Remove a work-around.

Remove the innodb_undo suite, and move and adapt the tests.
Remove unnecessary restarts, and add innodb_page_size_small.inc
for combinations.

innodb.undo_truncate is the merge of innodb_undo.truncate
and innodb_undo.truncate_multi_client.

Add the global status variable innodb_undo_truncations.
Without this, the test innodb.undo_truncate would occasionally
report that truncation did not happen. The test was only waiting
for the history list length to reach 0, but the undo tablespace
truncation would only take place some time after that.

Undo tablespace truncation will only occasionally occur with
innodb_page_size=32k, and typically never occur (with this amount
of undo log operations) with innodb_page_size=64k. We disable
these combinations.

innodb.undo_truncate_recover was formerly called
innodb_undo.truncate_recover.

Implement undo tablespace truncation via normal redo logging.

Implement TRUNCATE TABLE as a combination of RENAME to #sql-ib name,
CREATE, and DROP.

Note: Orphan #sql-ib*.ibd may be left behind if MariaDB Server 10.2
is killed before the DROP operation is committed. If MariaDB Server 10.2
is killed during TRUNCATE, it is also possible that the old table
was renamed to #sql-ib*.ibd but the data dictionary will refer to the
table using the original name.

In MariaDB Server 10.3, RENAME inside InnoDB is transactional,
and #sql-* tables will be dropped on startup. So, this new TRUNCATE
will be fully crash-safe in 10.3.

ha_mroonga::wrapper_truncate(): Pass table options to the underlying
storage engine, now that ha_innobase::truncate() will need them.

rpl_slave_state::truncate_state_table(): Before truncating
mysql.gtid_slave_pos, evict any cached table handles from
the table definition cache, so that there will be no stale
references to the old table after truncating.

== TRUNCATE TABLE ==

WL#6501 in MySQL 5.7 introduced separate log files for implementing
atomic and crash-safe TRUNCATE TABLE, instead of using the InnoDB
undo and redo log. Some convoluted logic was added to the InnoDB
crash recovery, and some extra synchronization (including a redo log
checkpoint) was introduced to make this work. This synchronization
has caused performance problems and race conditions, and the extra
log files cannot be copied or applied by external backup programs.

In order to support crash-upgrade from MariaDB 10.2, we will keep
the logic for parsing and applying the extra log files, but we will
no longer generate those files in TRUNCATE TABLE.

A prerequisite for crash-safe TRUNCATE is a crash-safe RENAME TABLE
(with full redo and undo logging and proper rollback). This will
be implemented in MDEV-14717.

ha_innobase::truncate(): Invoke RENAME, create(), delete_table().
Because RENAME cannot be fully rolled back before MariaDB 10.3
due to missing undo logging, add some explicit rename-back in
case the operation fails.

ha_innobase::delete(): Introduce a variant that takes sqlcom as
a parameter. In TRUNCATE TABLE, we do not want to touch any
FOREIGN KEY constraints.

ha_innobase::create(): Add the parameters file_per_table, trx.
In TRUNCATE, the new table must be created in the same transaction
that renames the old table.

create_table_info_t::create_table_info_t(): Add the parameters
file_per_table, trx.

row_drop_table_for_mysql(): Replace a bool parameter with sqlcom.

row_drop_table_after_create_fail(): New function, wrapping
row_drop_table_for_mysql().

dict_truncate_index_tree_in_mem(), fil_truncate_tablespace(),
fil_prepare_for_truncate(), fil_reinit_space_header_for_table(),
row_truncate_table_for_mysql(), TruncateLogger,
row_truncate_prepare(), row_truncate_rollback(),
row_truncate_complete(), row_truncate_fts(),
row_truncate_update_system_tables(),
row_truncate_foreign_key_checks(), row_truncate_sanity_checks():
Remove.

row_upd_check_references_constraints(): Remove a check for
TRUNCATE, now that the table is no longer truncated in place.

The new test innodb.truncate_foreign uses DEBUG_SYNC to cover some
race-condition like scenarios. The test innodb-innodb.truncate does
not use any synchronization.

We add a redo log subformat to indicate backup-friendly format.
MariaDB 10.4 will remove support for the old TRUNCATE logging,
so crash-upgrade from old 10.2 or 10.3 to 10.4 will involve
limitations.

== Undo tablespace truncation ==

MySQL 5.7 implements undo tablespace truncation. It is only
possible when innodb_undo_tablespaces is set to at least 2.
The logging is implemented similar to the WL#6501 TRUNCATE,
that is, using separate log files and a redo log checkpoint.

We can simply implement undo tablespace truncation within
a single mini-transaction that reinitializes the undo log
tablespace file. Unfortunately, due to the redo log format
of some operations, currently, the total redo log written by
undo tablespace truncation will be more than the combined size
of the truncated undo tablespace. It should be acceptable
to have a little more than 1 megabyte of log in a single
mini-transaction. This will be fixed in MDEV-17138 in
MariaDB Server 10.4.

recv_sys_t: Add truncated_undo_spaces[] to remember for which undo
tablespaces a MLOG_FILE_CREATE2 record was seen.

namespace undo: Remove some unnecessary declarations.

fil_space_t::is_being_truncated: Document that this flag now
only applies to undo tablespaces. Remove some references.

fil_space_t::is_stopping(): Do not refer to is_being_truncated.
This check is for tablespaces of tables. Potentially used
tablespaces are never truncated any more.

buf_dblwr_process(): Suppress the out-of-bounds warning
for undo tablespaces.

fil_truncate_log(): Write a MLOG_FILE_CREATE2 with a nonzero
page number (new size of the tablespace in pages) to inform
crash recovery that the undo tablespace size has been reduced.

fil_op_write_log(): Relax assertions, so that MLOG_FILE_CREATE2
can be written for undo tablespaces (without .ibd file suffix)
for a nonzero page number.

os_file_truncate(): Add the parameter allow_shrink=false
so that undo tablespaces can actually be shrunk using this function.

fil_name_parse(): For undo tablespace truncation,
buffer MLOG_FILE_CREATE2 in truncated_undo_spaces[].

recv_read_in_area(): Avoid reading pages for which no redo log
records remain buffered, after recv_addr_trim() removed them.

trx_rseg_header_create(): Add a FIXME comment that we could write
much less redo log.

trx_undo_truncate_tablespace(): Reinitialize the undo tablespace
in a single mini-transaction, which will be flushed to the redo log
before the file size is trimmed.

recv_addr_trim(): Discard any redo logs for pages that were
logged after the new end of a file, before the truncation LSN.
If the rec_list becomes empty, reduce n_addrs. After removing
any affected records, actually truncate the file.

recv_apply_hashed_log_recs(): Invoke recv_addr_trim() right before
applying any log records. The undo tablespace files must be open
at this point.

buf_flush_or_remove_pages(), buf_flush_dirty_pages(),
buf_LRU_flush_or_remove_pages(): Add a parameter for specifying
the number of the first page to flush or remove (default 0).

trx_purge_initiate_truncate(): Remove the log checkpoints, the
extra logging, and some unnecessary crash points. Merge the code
from trx_undo_truncate_tablespace(). First, flush all to-be-discarded
pages (beyond the new end of the file), then trim the space->size
to make the page allocation deterministic. At the only remaining
crash injection point, flush the redo log, so that the recovery
can be tested.

recv_addr_state, recv_addr_t: Define in log0recv.cc only.

Because innodb_file_per_table can be enabled at runtime after it
was disabled at startup, it is better to always register the same
innobase_hton->tablefile_extensions. Besides,
innodb_file_per_table=OFF does not prevent loading tables that may
have been created earlier with the .ibd file extension.

Remove plugin-load option from mariabackup. It does not needed to be an
option (we only need to store the plugin-load value during backup phase,
and reuse the same value during --prepare).

Fix is to read plugin-load from backup-my.cnf during prepare.

Fix exit condition for the log copying thread.

(https://github.com/facebook/rocksdb/issues/4344)
Also, disable /permissive- flag if set, it breaks rocksdb compilation
in 10.3 on older versions of Windows 8.1 SDK.

It uses --slave-use-idempotent-for-recovery which is not available in MariaDB.

Remove the mismatch betwen list of man pages in CMakeLists.txt and
actual files.

Direct IO doesnt work on all filesystems, e.g. it doesnt work on the
disk of kvm-bintar-trusty-amd64.

- Made output to be aligned in aria_chk -d
- Aria engine error texts are now written instead of "Undefined error"
- When running with --check --force, tables with wrong TRN's but otherwise
  correct are now zerofilled
- Fixed several bugs in check and recovery related to fulltext
- When doing recovery, store highest found TRID in aria_control_file
  Before this, the