`ha_heap::clone` was creating a handler by share's handlerton, which is
partition handlerton.
handler's handlerton should be used instead.
Here in particular, HEAP handlerton will be used and it will create ha_heap
handler.
The bug was fixed by MDEV-22599 bugfix, which changed `Field::cmp` call
to `Field::cmp_prefix` in `TABLE::check_period_overlaps`.
The trick is that `Field_bit::cmp` apparently calls `Field_bit::cmp_key`,
which condiders an argument an actual pointer to data, which isn't correct
for `Field_bit`, since it stores data by `bit_ptr`. which is in the
beginning of the record, and using `ptr` is incorrect (we use it through
`ptr_in_record` call)
After Sergei's cleanup this assertion is not actual anymore -- we can't
predict if the handler was used for lookup, especially in multi-update
scenario.
`position(old_data)` is made earlier in `ha_check_overlaps`, therefore it
is guaranteed that we compare right refs.
The problem here was that ha_check_overlaps internally uses ha_index_read,
which in case of fail overwrites table->status. Even though the handlers
are different, they share a common table, so the value is anyway spoiled.
This is bad, and table->status is badly designed and overweighted by
functionality, but nothing can be done with it, since the code related to
this logic is ancient and it's impossible to extract it with normal effort.
So let's just save and restore the value in ha_update_row before and after
the checks.
Other operations like INSERT and simple UPDATE are not in risk, since they
don't use this table->status approach.
DELETE does not do any unique checks, so it's also safe.
Insert worked incorrect as well. RocksDB used table->record[0] internally to store some
intermediate results for key conversion, during index searching among other operations.
So table->record[0] is spoiled during ha_rnd_index_map in ha_check_overlaps, so in turn
the broken record data was inserted.
The fix is to store RocksDB intermediate result in its own buffer instead of table->record[0].
`rocksdb` MTR suite is is checked and runs fine.
No need for additional tests. The existing overlaps.test covers the case completely.
However, I am not going to add anything related to rocksdb to suite, to keep it away
from additional dependencies.
To run tests with RocksDB engine, one can add following to engines.combinations:
[rocksdb]
plugin-load=$HA_ROCKSDB_SO
default-storage-engine=rocksdb
rocksdb
* The overlaps check is implemented on a handler level per row command.
It creates a separate cursor (actually, another handler instance) and
caches it inside the original handler, when ha_update_row or
ha_insert_row is issued. Cursor closes on unlocking the handler.
* Containing the same key in index means unique constraint violation
even in usual terms. So we fetch left and right neighbours and check
that they have same key prefix, excluding from the key only the period part.
If it doesnt match, then there's no such neighbour, and the check passes.
Otherwise, we check if this neighbour intersects with the considered key.
* The check does not introduce new error and fails with ER_DUPP_KEY error.
This might break REPLACE workflow and should be fixed separately
