btr_cur_instant_root_init(): Check the "infimum" and "supremum"
record strings already here, and not later in btr_cur_instant_root_init().
In this way, we can properly reject files from later versions where
instant ALTER TABLE could support further operations that change the
format of InnoDB clustered indexes.

For dropped columns, store the NOT NULL flag, the fixed length,
and for variable-length columns, whether the maximum length exceeded
255 bytes.

For partitioned tables, we must adjust each partition separately.

FIXME: For dropped columns, store the nullability and the fixed_len
in the BLOB array. Also, add a version discriminator field.

btr_cur_instant_init_low(): Read and validate the metadata BLOB page
before reconstructing the dictionary information based on it.

dict_col_t::clear_instant(): Renamed from remove_instant().
Do not assert that the column was instantly added, because we
sometimes call this unconditionally for all columns.

dict_table_t::reconstruct_columns(): Take the metadata BLOB
and length as a parameter. Invoke dict_index_t::reconstruct_fields()
upon successful completion.

For instant DROP COLUMN and ROW_FORMAT=COMPACT or ROW_FORMAT=REDUNDANT,
we must store the n_core_null_bytes in the root page, so that the
chain of node pointer records can be followed in order to reach the
leftmost leaf page where the metadata record is located.

If the PRIMARY KEY contains any variable-length column and some
nullable columns were instantly dropped, the dict_index_t::n_nullable
in the data dictionary could be smaller than it actually is in the
non-leaf pages. Because of this, the non-leaf pages could use more
bytes for the null flags than the data dictionary expects, and we
could be reading the lengths of the variable-length columns from the
wrong offset, and thus reading the child page number from wrong place.
This is the result of two design mistakes that involve unnecessary
storage of data: First, it is nonsense to store any data fields for
the leftmost node pointer records, because the comparisons would be
resolved by the MIN_REC_FLAG alone. Second, there cannot be any null
fields in the clustered index node pointer fields, but we nevertheless
reserve space for all the null flags.

btr_set_instant(): Convert a root page into "instant ALTER TABLE"
format. This replaces page_set_instant().

btr_cur_instant_init_metadata(): Do not read any lengths from the
metadata record header before reading the BLOB. At this point, we
would not actually know how many nullable fields the metadata record
contains.

btr_cur_instant_init_low(): Minimize differences from the 10.3 version.

btr_cur_instant_root_init(): Initialize n_core_null_bytes in one
of two possible ways.

FIXME: innobase_instant_try(): When needed, convert the root page
from the ADD COLUMN format to the generic instant ALTER TABLE format.

Because changes of the FIL_PAGE_TYPE or PAGE_INSTANT in the root
page are not undo-logged, it is possible that the fields suggest
that instant ADD COLUMN is in effect, even though no metadata
record exists. If the fields are set, proceed to fetch the
metadata record. If the metadata record does not exist, return
success if !index->is_instant().

Also, check that the "infimum" and "supremum" records carry the
strings in the root page. In a later format that supports instant
DROP COLUMN, we will have to store more information in the root
page, so that index->n_core_null_bytes can be determined accurately.

btr_cur_instant_init_low(): If columns were instantly added and dropped,
then index->is_instant() might not hold even though the root page type
was FIL_PAGE_TYPE_INSTANT. MariaDB 10.3 must refuse to open such files,
because instant DROP COLUMN is not supported.

Also, refuse to open the table if the metadata record has
wrong info OR status bits. Previously, we only refused to open
if both bits were wrong.

Apparently, the first fields of a clustered index may be updated
in an update_undo vector when the index is ID_IND of SYS_FOREIGN,
as part of renaming the table during ALTER TABLE.
Normally, updates of the PRIMARY KEY should be logged as
delete-mark and an insert.

The function had only one caller.

trx_undo_update_rec_get_update(): Handle the metadata BLOB correctly.

Correctly calculate the size of mblob when some last fields are missing.

MDEV-16211 Contents of transaction_registry should not be replicated by Galera

Addition based on Travis results

             truncating a temporary table

TRUNCATE expects only one TABLE instance (which is used by TRUNCATE
itself) to be open. However this requirement wasn't enforced after
"MDEV-5535: Cannot reopen temporary table".

Fixed by closing unused table instances before performing TRUNCATE.

Patch fixes two bugs:
1) BEGIN_TIMESTAMP of MYSQL.TRANSACTION_REGISTY is '0-0-0' on replication record insertion
2) BEGIN_TIMESTAMP equals COMMMIT_TIMESTAMP in MYSQL.TRANSACTION_REGISTRY

Fixed by calling THD::set_time() at appropriate places

For other than the clustered index, ignore table->instant.

ha_innobase::check_if_supported_inplace_alter(): Do not allow
adding a FTS_DOC_ID column if a hidden FTS_DOC_ID column exists
due to FULLTEXT INDEX. (This always required ALGORITHM=COPY.)

ha_innobase_inplace_ctx::first_alter_pos: The first column whose position
is affected by instant ADD, DROP, or changing the order of columns.

innobase_instant_try(): Fill in a zero default value for the hidden column
FTS_DOC_ID. Before this, it was not possible to instantly add columns if
a hidden FTS_DOC_ID column existed (at the end of the InnoDB table
definition).

A cleanup for MDEV-17317 Add THD* parameter into Item::get_date() and stricter data type control to "fuzzydate"

Fixing C++ function check_date() to get the "fuzzydate" as
date_mode_t rather than ulonglong, so conversion from
date_time_t to ulonglong is now done inside C++ check_date(),
and no conversion is needed in the callers' code.

As an additional safety, modified the code not to pass
TIME_FUZZY_DATE to the low level C functions:
- check_date()
- str_to_datetime()
- str_to_time()
- number_to_datetime()
because TIME_FUZZY_DATE is known only on the C++ level,
C functions do not know it.

Soon we'll be adding more flags into the C++ level (i.e. to date_time_t),
e.g. for rounding. It's a good idea to prevent passing C++ specific
flags into pure C routines before this change.

Asserts were added into the affected C functions to verify
that the caller passed only known C level flags.

instant_metadata(): Create a metadata record for instant ALTER TABLE.

rec_offs_nth_extern_old() was introduced in
commit a4948daf
and never used.