rec_init_offsets(): Relax the assertion that was added in
commit 01f45bec
to catch ROW_FORMAT=REDUNDANT records that have fewer fields
than expected.

This assertion would fail when accessing the records of the
built-in InnoDB table SYS_INDEXES. The column MERGE_THRESHOLD
had been effectively instantly added in MariaDB Server 10.2
(and MySQL 5.7), but is_instant() does not hold for that index.
Relax the assertion, so that it will not fail in this case.

MDEV-20813 Assertion failure in buf_flush_init_for_writing() for innodb_immediate_scrub_data_uncompressed=ON

The assertion that was added in
commit c0c003be
to augment the fix of MDEV-20805 turns out to be invalid when
innodb_immediate_scrub_data_uncompressed is enabled.
In this mode, fsp_init_file_page() will be invoked on data pages
that have been freed, causing writes of almost-all-zero pages.

btr_page_free(): Adjust the comment.

buf_flush_init_for_writing(): Disable the assertion with a note
that it should be re-enabled in MDEV-15528.

When the mysqld_multi script passes the --defaults-group-suffix
option to mysqld, it must remove the initial substring with the
group name ("mysqld") from option value, because otherwise substring
"mysqld" will be added to the group name and then the group name
will contain the word "mysqld" twice, which is wrong, because
mysqld itself adds the suffix received to the group name.

When the mysqld_multi script passes the --defaults-group-suffix
option to mysqld, it must remove the initial substring with the
group name ("mysqld") from option value, because otherwise substring
"mysqld" will be added to the group name and then the group name
will contain the word "mysqld" twice, which is wrong, because
mysqld itself adds the suffix received to the group name.

When the mysqld_multi script passes the --defaults-group-suffix
option to mysqld, it must remove the initial substring with the
group name ("mysqld") from option value, because otherwise substring
"mysqld" will be added to the group name and then the group name
will contain the word "mysqld" twice, which is wrong, because
mysqld itself adds the suffix received to the group name.

When the mysqld_multi script passes the --defaults-group-suffix
option to mysqld, it must remove the initial substring with the
group name ("mysqld") from option value, because otherwise substring
"mysqld" will be added to the group name and then the group name
will contain the word "mysqld" twice, which is wrong, because
mysqld itself adds the suffix received to the group name.

This is another follow-up fix to
commit b393e2cb
which turned out to be still broken.

Replace the C++11 keyword 'constexpr' with #define.

debug_sync_t::str: Remove the zero-length array.
Replace sync->str with reinterpret_cast<char*>(&sync[1]).

During IMPORT TABLESPACE, we do invoke
buf_flush_init_for_writing() with block==NULL and newest_lsn!=0.

Remove unused variables and type mismatch that was introduced
in commit b393e2cb

Also, fix a typo in the documentation of the parameter, and
update the test.

buf_flush_init_for_writing(): Assert that FIL_PAGE_TYPE is set
except when creating a new data file with a dummy first page.

buf_dblwr_create(): Ensure that FIL_PAGE_TYPE on all pages
will be initialized. Reset buf_dblwr_being_created at the end.

In the function recv_parse_or_apply_log_rec_body() there are debug checks
for validating the state of the page when redo log records are being
applied. Most notably, FIL_PAGE_TYPE should be set before anything else
is being written to the page.

ibuf_add_free_page(): Set FIL_PAGE_TYPE before performing any other changes.

Apply the correct pattern for debug instrumentation:

SET @save_dbug=@@debug_dbug;
SET debug_dbug='+d,...';
...
SET debug_dbug=@save_dbug;

Numerous tests use statements of the form

SET debug_dbug='-d,...';

which will inadvertently enable all DBUG tracing output,
causing unnecessary waste of resources.

The test main.index_merge_innodb is taking very much time,
especially on later versions (10.2 and 10.3).

Some of this could be attributed to the use of INSERT...SELECT,
which is time-consumingly creating explicit record locks in InnoDB
for the locking read in the SELECT part.

In 10.3 and later, some slowness can be attributed to MDEV-12288,
which makes the InnoDB purge thread spend time to reset transaction
identifiers in the inserted records. If we prevent purge from
running before all tables are dropped, the test seems to be
10% faster on an unoptimized debug build on 10.5. (A proper fix
would be to implement MDEV-515 and stop writing row-level undo log
records for inserts into an empty table or partition.)

At the same time, it should not hurt to make main.index_merge_myisam
to use the sequence engine. Not only could it be a little faster,
but the test would be slightly more readable.

the bug was already fixed in MDEV-17005, so now only test is added

In commit 0f7732d1
we introduced a innodb_checksum_algorithm=full_crc32 combination
to a number of encryption tests, and also fixed the code accordingly.

The default in MariaDB 10.5 is innodb_checksum_algorithm=full_crc32.
In a test merge to 10.5, the test encryption.innodb-redo-badkey failed
once due to a message that had been added in that commit.

Let us introduce a full_crc32 option to that test.
And let us use strict_crc32 and strict_full_crc32 instead of the
non-strict variants, for the previously augmented tests, to be in
line with the earlier tests encryption.corrupted_during_recovery and
encryption.innodb_encrypt_temporary_tables.

btr_page_get_split_rec_to_left(): Assert that in the leftmost leaf page,
if the metadata record exists, index->is_instant() must hold.
The assertion of commit 01f45bec
could fail during innobase_instant_try().

btr_page_get_split_rec_to_left(): Assert that in the leftmost leaf page,
the metadata record exists if and only if index->is_instant().

page_validate(): Correct the wording of a message.

rec_init_offsets(): Assert that whenever a record is in "instant ALTER"
format, index->is_instant() must hold.

In MDEV-11369 (instant ADD COLUMN) in MariaDB Server 10.3,
we introduced the hidden metadata record that must be the
first record in the clustered index if and only if
index->is_instant() holds.

To catch MDEV-19783, in
commit ed0793e0 and
commit 99dc40d6
we added some assertions to find cases where
the metadata record is missing while it should not be, or a
record exists when it should not. Those assertions were invalid
when traversing the PAGE_FREE list. That list can contain anything;
we must only be able to determine the successor and the size of
each garbage record in it.

page_validate(), page_simple_validate_old(), page_simple_validate_new():
Do not invoke page_rec_get_next_const() for traversing the PAGE_FREE
list, but instead use a lower-level accessor that does not attempt to
validate the REC_INFO_MIN_REC_FLAG.

page_copy_rec_list_end_no_locks(),
page_copy_rec_list_start(), page_delete_rec_list_start():
Add assertions.

btr_page_get_split_rec_to_left(): Remove a redundant return value,
and make the output parameter the return value.

btr_page_get_split_rec_to_right(), btr_page_split_and_insert(): Clean up.

When MDEV-12026 introduced innodb_checksum_algorithm=full_crc32 in
MariaDB 10.4, it accidentally added a dependency on buf_page_t::encrypted.
Now that the flag has been removed, we must adjust the page-read routine.

buf_page_io_complete(): When the full_crc32 page checksum matches but the
tablespace ID in the page does not match after decrypting, we should
declare it a decryption failure and suppress the page dump output and
any attempts to re-read the page.

Fixed warning: -Woverloaded-virtual for GCC 9 (Clang treats it differently)

Caused by c9cba597

Fixed warnings: -Woverloaded-virtual, -Winconsistent-missing-override

Caused by c9cba597

/mariadb/10.3/wsrep/wsrep_gtid.c:45:26: error: conversion from 'long int' to 'unsigned int' may change value [-Werror=conversion]
   45 |                 offset = endptr - str;

While `handler::next_insert_id` is restored on duplicate key errors
`part_share->next_auto_inc_val` is not restored which causes
discrepancy.

TABLE::mark_columns_needed_for_update(): use_all_columns() assigns
pointer of all_set into read_set and write_set, but this is not good
since all_set is changed later by
TABLE::mark_columns_used_by_index_no_reset().

Do column_bitmaps_signal() whenever we change read_set/write_set.

MDEV-16210 FK constraints on versioned tables use historical rows, which may cause constraint violation

Constraint check is done on secondary index update.
F.ex. DELETE does row_upd_sec_index_entry() and checks constraints in
row_upd_check_references_constraints(). UPDATE is optimized for the
case when order is not changed (node->cmpl_info & UPD_NODE_NO_ORD_CHANGE)
and doesn't do row_upd_sec_index_entry(), so it doesn't check constraints.

Since for versioned DELETE we do UPDATE actually, but expect behaviour
of DELETE in terms of constraints, we should deny this optimization to
get constraints checked.

Fix wrong referenced table check when versioned DELETE inserts history in parent
table. Set check_ref to false in this case.

Removed unused dup_chk_only argument for row_ins_sec_index_entry() and
added check_ref argument.

MDEV-18057 fix was superseded by this fix and reverted.

foreign.test:
All key_type combinations: pk, unique, sec(ondary).