This is caused by following change:

commit 95d29c99f01882ffcc2259f62b3163f9b0e80c75
Author: Marko Mäkelä <marko.makela@oracle.com>
Date:   Tue Nov 27 11:12:13 2012 +0200

    Bug#15920445 INNODB REPORTS ER_DUP_KEY BEFORE CREATE UNIQUE INDEX COMPLETED

    There is a phase during online secondary index creation where the index has
    been internally completed inside InnoDB, but does not 'officially' exist yet.
    We used to report ER_DUP_KEY in these situations, like this:

    ERROR 23000: Can't write; duplicate key in table 't1'

    What we should do is to let the 'offending' operation complete, but report an
    error to the
    ALTER TABLE t1 ADD UNIQUE KEY (c2):

    ERROR HY000: Index c2 is corrupted
    (This misleading error message should be fixed separately:
    Bug#15920713 CREATE UNIQUE INDEX REPORTS ER_INDEX_CORRUPT INSTEAD OF DUPLICATE)

    row_ins_sec_index_entry_low(): flag the index corrupted instead of
    reporting a duplicate, in case the index has not been published yet.

    rb:1614 approved by Jimmy Yang

Problem is that after we have found duplicate key on primary key
we continue to get necessary gap locks in secondary indexes to
block concurrent transactions from inserting the searched records.
However, search from unique index used in foreign key constraint
could return DB_NO_REFERENCED_ROW if INSERT .. ON DUPLICATE KEY UPDATE
does not contain value for foreign key column. In this case
we should return the original DB_DUPLICATE_KEY error instead
of DB_NO_REFERENCED_ROW.

Consider as a example following:

create table child(a int not null primary key,
b int not null,
c int,
unique key (b),
foreign key (b) references
parent (id)) engine=innodb;

insert into child values (1,1,2);

insert into child(a) values (1) on duplicate key update c = 3;

Now primary key value 1 naturally causes duplicate key error that will be
stored on node->duplicate. If there was no duplicate key error, we should
return the actual no referenced row error. As value for column b used in
both unique key and foreign key is not provided, server uses 0 as a
search value. This is naturally, not found leading to DB_NO_REFERENCED_ROW.
But, we should update the row with primay key value 1 anyway as
requested by on duplicate key update clause.

Fix of nondebuging version issue

than the query itself

ACL checks were not properly supported for tables used in CTE
specifications. This patch fixes the problem.

        Check for the empty 'coordinates' array.

        Character bigger than 0x60 wasn't handled properly
        inside a numeric constant.

This patch effectively blocks the optimization that uses multiple
equalities for ORDER BY to remove tmp table in the case when
the first table happens to be the result of materialization of
a semi-join nest. Currently there is no code at the execution level
that would support the optimization in this case.

rec_get_offsets_func(): Relax a bogus debug assertion.
It would fail when we are operating on a copied prefix
of a node pointer record.

row_log_table_apply_op(): Remove references to dict_table_t::n_vcols.
Virtual column information is no longer being written to the log.

row_log_t: Remove the unused fields n_old_col, n_old_vcol.

When MySQL 5.7 introduced indexed virtual columns, it introduced
several bugs into the online table-rebuilding ALTER, that is,
the row_log_table_apply() family of functions.

The online_log format that was introduced for online table-rebuilding
ALTER in MySQL 5.6 should be sufficient. Ideally, any indexed virtual
column values would be evaluated based on the log records in the temporary
file. There is no need to log virtual column values.

(For ADD INDEX, that is row_log_apply(), we always must log the values of
the keys, no matter if the columns are virtual.)

Because omitting the virtual column values removes any chance of
row_log_table_apply() working with indexed virtual columns, we
will for now refuse LOCK=NONE in table-rebuilding ALTER operations
when indexes on virtual columns exist. This restriction would be
lifted in MDEV-14341.

innobase_indexed_virtual_exist(): New predicate, to determine if
indexed virtual columns exist in a table definition.

ha_innobase::check_if_supported_inplace_alter(): Refuse online rebuild
if indexed virtual columns exist.

rec_get_converted_size_temp_v(), rec_convert_dtuple_to_temp_v(): Remove.

row_log_table_delete(), row_log_table_update(, row_log_table_insert():
Remove parameters for virtual columns.

trx_undo_read_v_rows(): Remove the col_map parameter.

row_log_table_apply(): Do not deal with virtual columns.

MDEV-14333 Mariabackup --apply-log-only crashes if incomplete transactions with update_undo logs are present

trx_undo_free_prepared(): Relax the assertion for
mariabackup --apply-log-only.

MDEV-14164: Unknown column error when adding aggregate to function in oracle style procedure FOR loop

Make differentiation between pullout for merge and pulout of outer field during exists2in transformation.
In last case the field was outer and so we can safely start from name resolution context of the SELECT where it was pulled.
Old behavior lead to inconsistence between list of tables and outer name resolution context (which skips one SELECT for merge purposes) which creates problem vor name resolution.

There was a problem in the recent patch for MDEV-10817:
get_date() must "return true" on null_value rather than "return 0"

(forgot to fix Item_sum_hybrid::get_date() after copying and pasting
from Item_sum_hybrid::val_str()).

FlushObserver::flush(): Never discard unwritten changes.
We do not want to risk corrupting the system tablespace
or .ibd files that are not part of a table-rebuilding ALTER.

Ever since MDEV-10813 cleaned up InnoDB use of atomic memory operations
and made buf_block_fix() an atomic operation, some conditions around
buf_block_fix() have been unnecessary.

This problem was earlier fixed by the patch for MDEV-8910. Adding tests only.

The bug was fixed by the patch for the bug mdev-13780.

With a big buffer pool that contains many data pages,
DISCARD TABLESPACE took a long time, because it would scan the
entire buffer pool to remove any pages that belong to the tablespace.
With a large buffer pool, this would take a lot of time, especially
when the table-to-discard is empty.

The minimum amount of work that DISCARD TABLESPACE must do is to
remove the pages of the to-be-discarded table from the
buf_pool->flush_list because any writes to the data file must be
prevented before the file is deleted.

If DISCARD TABLESPACE does not evict the pages from the buffer pool,
then IMPORT TABLESPACE must do it, because we must prevent pre-DISCARD,
not-yet-evicted pages from being mistaken for pages of the imported
tablespace.

It would not be a useful fix to simply move the buffer pool scan to
the IMPORT TABLESPACE step. What we can do is to actively evict those
pages that could be mistaken for imported pages. In this way, when
importing a small table into a big buffer pool, the import should
still run relatively fast.

Import is bypassing the buffer pool when reading pages for the
adjustment phase. In the adjustment phase, if a page exists in
the buffer pool, we could replace it with the page from the imported
file. Unfortunately I did not get this to work properly, so instead
we will simply evict any matching page from the buffer pool.

buf_page_get_gen(): Implement BUF_EVICT_IF_IN_POOL, a new mode
where the requested page will be evicted if it is found. There
must be no unwritten changes for the page.

buf_remove_t: Remove. Instead, use trx!=NULL to signify that a write
to file is desired, and use a separate parameter bool drop_ahi.

buf_LRU_flush_or_remove_pages(), fil_delete_tablespace():
Replace buf_remove_t.

buf_LRU_remove_pages(), buf_LRU_remove_all_pages(): Remove.

PageConverter::m_mtr: A dummy mini-transaction buffer

PageConverter::PageConverter(): Complete the member initialization list.

PageConverter::operator()(): Evict any 'shadow' pages from the
buffer pool so that pre-existing (garbage) pages cannot be mistaken
for pages that exist in the being-imported file.

row_discard_tablespace(): Remove a bogus comment that seems to
refer to IMPORT TABLESPACE, not DISCARD TABLESPACE.