MDEV-16210 original case was wrongly allowed versioned DELETE from
referenced table where reference is by non-primary key. InnoDB UPDATE
has optimization for new rows not changing its clustered index
position. In this case InnoDB doesn't update all secondary indexes and
misses the one holding the referenced key. The fix was to disable this
optimization for versioned DELETE. In case of versioned DELETE we
forcely update all secondary indexes and therefore check them for
constraints.

But the above fix raised another problem with versioned DELETE on
foreign table side. In case when there was no corresponding record in
referenced table (illegal foreign reference can be done with "set
foreign_key_checks=off") there was spurious constraint check (because
versioned DELETE is actually UPDATE) and hence the operation failed
with constraint error.

MDEV-16210 tried to fix the above problem by checking foreign table
instead of referenced table and that at least was illegal.

Constraint check is done by row_ins_check_foreign_constraint() no
matter what kind of table is checked, referenced or foreign
(controlled by check_ref argument).

Referenced table is checked by row_upd_check_references_constraints().
Foreign table is checked by row_ins_check_foreign_constraints().

Current fix rolls back the wrong fix for the above problem and
disables referenced table check for DELETE on foreign side by
introducing `check_foreign` argument which when set to *false* skips
row_ins_check_foreign_constraints() call.

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.

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

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.

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).

Preparation for MDEV-16210:

replace.test:
key_type combinations: PK and UNIQUE.

foreign.test:
Preparation for key_type combinations.

Other fixes:

* Merged versioning.update2 into versioning.update;
* Removed test2 database and done individual drop instead.

The function was always called with lsn=LSN_MAX.
Remove that redundant parameter.

Spotted by Thirunarayanan Balathandayuthapani.

The field buf_page_t::encrypted was added in MDEV-8588.
It was made mostly redundant in MDEV-12699. Remove the field.

calc_field_event_length(): For type=MYSQL_TYPE_BLOB and meta==0,
return 0 instead of *ptr+1. This was noted by -Wimplicit-fallthrough.

(fix and explanation came with MDEV-20753 (duplicate of this bug))

Do not try to push down conditions to engine if query was resolved without tables (and so the engine).