After a failed ADD INDEX, dict_index_remove_from_cache_low()
could iterate the index fields and dereference a freed virtual
column object when trying to remove the index from the v_indexes
of the virtual column.

This regression was caused by a merge of
MDEV-16119 InnoDB lock->index refers to a freed object.

ha_innobase_inplace_ctx::clear_added_indexes(): Detach the
indexes of uncommitted indexes from virtual columns, so that
the iteration in dict_index_remove_from_cache_low() can be avoided.

ha_innobase::prepare_inplace_alter_table(): Ignore uncommitted
corrupted indexes when rejecting ALTER TABLE. (This minor bug was
revealed by the extension of the test case.)

dict_index_t::detach_columns(): Detach an index from virtual columns.
Invoked by both dict_index_remove_from_cache_low() and
ha_innobase_inplace_ctx::clear_added_indexes().

dict_col_t::detach(const dict_index_t& index): Detach an index from
a column.

dict_col_t::is_virtual(): Replaces dict_col_is_virtual().

dict_index_t::has_virtual(): Replaces dict_index_has_virtual().

log_crypt_101_read_block(): Mimic MariaDB 10.1, and use the first
encryption key if the key for the checkpoint cannot be found.
Redo log encryption key rotation was ultimately disabled
in MDEV-9422 (MariaDB 10.1.13) due to design issues. So, from
MariaDB 10.1.13 onwards only one log encryption key should matter.

recv_log_format_0_recover(): Add the parameter 'bool crypt'.
Indicate when the log cannot be decrypted for upgrade, instead of
making a possibly false claim that the log requires crash recovery.

init_crypt_key(): Remove extra space from a message.

Just spacing out the links on separate linkes, they were running together
in a block of text and could be a little hard for some people to
differentiate where one begins and the next ends. Seems silly, but just
trying to help in the formatting a bit.

This bug caused crashes for queries with unreferenced non-recursive
CTEs specified by unions.It happened because the function
st_select_lex_unit::prepare() tried to use the value of the field 'derived'
that could not be set for unferenced CTEs as there was no derived
table associated with an unreferenced CTE.

Also fixes MDEV-14727, MDEV-14491
InnoDB: Error: Waited for 5 secs for hash index ref_count (1) to drop to 0
by replacing the flawed wait logic in dict_index_remove_from_cache_low().

On DISCARD TABLESPACE, there is no need to drop the adaptive hash index.
We must drop it on IMPORT TABLESPACE, and eventually on DROP TABLE or
DROP INDEX. As long as the dict_index_t object remains in the cache
and the table remains inaccessible, the adaptive hash index entries
to orphaned pages would not do any harm. They would be dropped when
buffer pool pages are reused for something else.

btr_search_drop_page_hash_when_freed(), buf_LRU_drop_page_hash_batch():
Remove the parameter zip_size, and pass 0 to buf_page_get_gen().

buf_page_get_gen(): Ignore zip_size if mode==BUF_PEEK_IF_IN_POOL.

buf_LRU_drop_page_hash_for_tablespace(): Drop the adaptive hash index
even if the tablespace is inaccessible.

buf_LRU_drop_page_hash_for_tablespace(): New global function, to drop
the adaptive hash index.

buf_LRU_flush_or_remove_pages(), fil_delete_tablespace():
Remove the parameter drop_ahi.

dict_index_remove_from_cache_low(): Actively drop the adaptive hash index
if entries exist. This should prevent InnoDB hangs on DROP TABLE or
DROP INDEX.

row_import_for_mysql(): Drop any adaptive hash index entries for the table.

row_drop_table_for_mysql(): Drop any adaptive hash index for the table,
except if the table resides in the system tablespace. (DISCARD TABLESPACE
does not apply to the system tablespace, and we do no want to drop the
adaptive hash index for other tables than the one that is being dropped.)

row_truncate_table_for_mysql(): Drop any adaptive hash index entries for
the table, except if the table resides in the system tablespace.

When the transaction isolation level is SERIALIZABLE, or when
a locking read is performed in the REPEATABLE READ isolation level,
InnoDB must lock delete-marked records in order to prevent another
transaction from inserting something.

However, at READ UNCOMMITTED or READ COMMITTED isolation level or
when the parameter innodb_locks_unsafe_for_binlog is set, the
repeatability of the reads does not matter, and there is no need
to lock any records.

row_search_for_mysql(): Skip locks on delete-marked committed records
upfront, instead of invoking row_unlock_for_mysql() afterwards.
The unlocking never worked for secondary index records.

MDEV-13834 10.2 wrongly recognizes 10.1.10 innodb_encrypt_log=ON data as after-crash and refuses to start

infos[]: Allocate enough entries to accommodate all keys from both
checkpoint pages.

infos_used: The size of infos[].

get_crypt_info(): Merge to the only caller, log_crypt_101_read_block().

log_crypt_101_read_block(): Do not validate the log block checksum,
because it will not be valid when upgrading from MariaDB 10.1.10.
Instead, check that the encryption key exists.

log_crypt_101_read_checkpoint(): Append to infos[] instead of overwriting.

Use a compatible xargs command-line arguments.

Problem was that max_row_lengt() used different bitmap
than pack_row()

Crash happened because in discover, table->work_part_info was not properly
reset before execution.
Fixed by resetting before calling execute alter table, create table or
mysql_create_frm_image.

When merging this with 10.2 and later, one can just use the 10.2 or later code

Problem was that blob memory allocated in Table_trigger_list was not
properly freed

Close MYSQL (and destroy THD) in the same thread where it was used,
because THD embeds MDL_context, that owns some LF_PINS, that remember
a pointer to my_thread_var->stack_ends_here.

Don't check global_memory_used if
debug_assert_on_not_freed_memory is not set

ha_archive::max_row_length() and ha_archive::pack_row()
didn't use record parameter properly. Especially testing
of null was wrong for record[1]

The cause of this was several different bugs:

- When using binary logging with binlog_row_image=FULL
  the all bits in read_set was set, which caused a
  different (wrong) pattern for marking vcol_set.
- TABLE::mark_virtual_columns_for_write() didn't in all
  cases mark vcol_set with the vcol_field.
- TABLE::update_virtual_fields() has to update all
  vcol fields on REPLACE if binary logging with FULL
  is used.
- VCOL_UPDATE_INDEXED should update all vcol fields part
  of an index that was not updated by VCOL_UPDATE_FOR_READ
- max_row_length() calculated length of NULL and not
  used fields. This didn't cause any crash, but used
  more memory than needed.

thd_destructor_proxy(): Ensure that purge actually exits,
like the logic should have been ever since MDEV-14080.

srv_purge_shutdown(): A new function to wait for the
purge coordinator to exit. Before exiting, the
purge coordinator will ensure that all purge workers have exited.

i_s_innodb_buffer_page_fill(), i_s_innodb_buf_page_lru_fill():
Only invoke Field::set_notnull() if the index was found.

This is the MariaDB 10.2 version of the patch.

field_store_string(): Simplify the code.

field_store_index_name(): Remove, and use field_store_string()
instead. Starting with MariaDB 10.2.2, there is the predicate
dict_index_t::is_committed(), and dict_index_t::name never
contains the magic byte 0xff.

Correct some comments to refer to TEMP_INDEX_PREFIX_STR.

i_s_cmp_per_index_fill_low(): Use the appropriate value NULL to
identify that an index was not found. Check that storing each
column value succeeded.

i_s_innodb_buffer_page_fill(), i_s_innodb_buf_page_lru_fill():
Only invoke Field::set_notnull() if the index was found.
(This fixes the bug.)

i_s_dict_fill_sys_indexes(): Adjust the index->name that was
directly loaded from SYS_INDEXES.NAME (which can start with
the 0xff byte). This was the only function that depended
on the translation in field_store_index_name().

Fix an obvious typo: replace_column should be applied to SHOW TABLE STATUS,
not to SELECT * FROM t1.

MDEV-16123 ASAN heap-use-after-free handler::ha_index_or_rnd_end
MDEV-13828 Segmentation fault on RENAME TABLE

Problem was that destructor called methods for closed table.
Fixed by removing code in destructor.

Crash happened when deleting all columns that was part of a check constraint

The bug was that read map for from table was used when
checking CHECK constraint and was not properly reset
in copy_data_between_tables()

Problem was that handle_if_exists_options() didn't correct
alter_info->flags when things was removed from the list.

Problem was that detection of temporary tables was all wrong for
RENAME TABLE.
(Temporary tables where opened by top level call to
open_temporary_tables(), which can't detect if a temporary table
was renamed to something and then reused).

Fixed by adding proper parsing of rename list to check against
the current name of a table at each rename stage.
Also change do_rename_temporary() to check against the current
state of temporary tables, not according to the state of start
of RENAME TABLE.

MDEV-10130 Assertion `share->in_trans == 0' failed in storage/maria/ma_close.c
MDEV-10378 Assertion `trn' failed in virtual int ha_maria::start_stmt

The problem was that maria_handler->trn was not properly reset
at commit/rollback and ha_maria::exernal_lock() could get confused
because.

There was some old code in ha_maria::implicit_commit() that tried
to take care of this, but it was not bullet proof.

Fixed by adding list of all tables that is part of the maria transaction to
TRN.

A nice side effect was of the fix is that loops in
ha_maria::implict_commit() got to be much simpler.

Other things:
- Fixed a bug in mysql_admin_table() where argument open_for_modify
  was wrongly reset for the next table in the chain
- rollback admin command also in case of fatal error.
- Split _ma_set_trn_for_table() to three version to simplify code
  and debugging.
- Several new asserts to detect the original problem (that file was
  not properly removed from trn before calling ma_close())

Step#1: RocksDB files require a special #define when they are compiled
with valgrind. Without that, valgrind fails with an 'unimplemented syscall'
error for fcntl call.