Type_handler_temporal_result::Item_func_min_max_fix_attributes()
in an expression GREATEST(string,date), e.g:

  SELECT GREATEST('1', CAST('2020-12-12' AS DATE));

incorrectly evaluated decimals as 6 (like for DATETIME).

Adding a separate virtual implementation:
  Type_handler_date_common::Item_func_min_max_fix_attributes()
This makes the code simpler.

The code in Item_func_int_val::fix_length_and_dec_int_or_decimal()
calculated badly the result data type for FLOOR()/CEIL(), so for example
the decimal(38,10) input created a decimal(28,0) result.
That was not correct, because one extra integer digit is needed.
   floor(-9.9) -> -10
   ceil(9.9)   ->  10

Rewritting the code in a more straightforward way.
Additional changes:
- FLOOR() now takes into account the presence of the UNSIGNED
flag of the argument: FLOOR(unsigned decimal) does not need an extra digits.
- FLOOR()/CEILING() now preserve the unsigned flag in the result
  data type is decimal.
These changes give nicer data types.

Problem:- rpl_parallel2 was failing non-deterministically
Analysis:-
When FLUSH TABLES WITH READ LOCK is executed, it will allow all worker
threads to complete their ongoing transactions and then it will pause them.
At this state FTWRL will proceed to acquire global read lock. FTWRL first
blocks threads from starting new commits, then upgrades the lock to block
commit of existing transactions.
  Step1:
    FLUSH TABLES WITH READ LOCK - Blocks new commits
  Step2:
    * STOP SLAVE command enables 'force_abort=1' which unblocks workers,
      they continue to execute events.
    * T1: Waits in 'record_gtid' call to update 'gtid_slave_pos' table with
      its current GTID, but it is blocked becuase of Step1.
    * T2: Holds COMMIT lock and waits for T1 to commit.
  Step3:
    FLUSH TABLES WITH READ LOCK - Waiting to get BLOCK_COMMIT.
This results in deadlock. When STOP SLAVE command allows paused workers to
proceed, workers should skip the execution of all further events, similar
to 'conservative' parallel mode.
Solution:-
We will assign 1 to skip_event_group when we are aborted in do_ftwrl_wait.
rpl_parallel_entry->pause_sub_id is only reset when force_abort is off in
rpl_pause_after_ftwrl.

Changing that in case of *INT and hex hybrid input:
- ROUND(x,NULL) creates a column with the same type as x.
  The old code created a DOUBLE column, which was not relevant at all.
  This change simplifies the code a lot.

- ROUND(x,non_constant) creates a column of the INT, BIGINT or DECIMAL
  data type (depending on the exact type of x).
  The old code created a column of the DOUBLE data type,
  which lead to precision loss. Hence MDEV-23366.

- ROUND(bigint_30,negative_constant) creates a column of the DECIMAL(30,0)
  data type. The old code created DECIMAL(29,0), which looked strange:
  the data type promoted to a higher one, but max length reduced.
  Now the length attribute is preserved.

failed or late ER_PERIOD_FIELD_WRONG_ATTRIBUTES upon attempt to create
existing table

Analysis: Error state is not stored when field is checked in
Table_period_info::check_field()
Fix: Store error state by setting res to true.

This problem was fixed by MDEV-23368. Adding tests only.

Item_func_round::fix_arg_int() did not take into account cases
when the result of ROUND(bigint_subject,negative_precision)
could go outside of the BIGINT range. The old code only incremented
max_length, but did not extend change the data type.
Fixing to extend the data type (together with max_length increment).

The condition in Item_func_round::fix_arg_int() to decide whether:
- we can preserve the data type of args[0] versus
- the result can go outside of the args[0] data type
was wrong.

The data type of the first argument can be preserved in these cases:
- TRUNCATE(x, n)
- ROUND(x, n>=0)

Fixing the condition accordingly.

On MariaDB 10.4 (commit 4db4b773),
the query results would not be sorted, which creates random result
differences. Let us explicitly sort the results already in 10.3
in order to avoid future merge trouble.

Fixing ROUND(date,0), TRUNCATE(date,x), FLOOR(date), CEILING(date)
to return the `int(8) unsigned` data type.

Details:
1. Cleanup: moving virtual implementations
   - Type_handler_temporal_result::Item_func_int_val_fix_length_and_dec()
   - Type_handler_temporal_result::Item_func_round_fix_length_and_dec()
   to Type_handler_date_common. Other temporal data type handlers
   override these methods anyway. So they were only DATE specific.
   This change makes the code clearer.
2. Backporting DTCollation_numeric from 10.5, to reuse the code easier.
3. Adding the `preferred_attrs` argument to Item_func_round::fix_arg_int(). Now
   Type_handler_xxx::Item_func_round_val_fix_length_and_dec() work as follows:
   - The INT-alike and YEAR handlers copy preferred_attrs from args[0].
   - The DATE handler passes explicit attributes, to get `int(8) unsigned`.
   - The hex hybrid handler passes NULL, so fix_arg_int() calculates attributes.
4. Type_handler_date_common::Item_func_int_val_fix_length_and_dec()
   now sets the type handler and attributes to get `int(8) unsigned`.

In case of NATURAL JOIN / USING mark all field (one table can not be opened
in any case so optimisation does not worth it).

IMHO table should be checked for used fields and filled after prepare,
when we will fave whole info about used fields but it is too big change
for a bugfix. Which will be made later by Serg patch

- Adding lock_wait_timeout value as 1 make sure that truncate table
fails instead of making MDL timeout.

The purpose of the InnoDB doublewrite buffer is to make InnoDB
tolerant against cases where the server was killed in the middle
of a page write. (In Linux, killing a process may interrupt a
write system call, typically on a 4096-byte boundary.)

There may exist multiple copies of a page number in the doublewrite
buffer. Recovery should choose the latest valid copy of the page.
By design, the FIL_PAGE_LSN must not precede the latest checkpoint LSN
nor be later than the end of the recovered log.

For page_compressed and encrypted pages, we were missing proper
consistency checks. In the 10.4 data set generated for in MDEV-23231,
the data file contained a valid page_compressed page, and an
identical copy of that page was also present in the doublewrite
buffer. But, recovery would incorrectly consider the page invalid
and restore an uncompressed copy of the same page that had been
written before the log checkpoint. (In fact, no redo log was to
be applied to that page.)

buf_dblwr_process(): Validate the FIL_PAGE_LSN in the doublewrite
buffer pages, and always skip page 0, because those pages should
have been recovered by Datafile::restore_from_doublewrite() if
necessary.

Datafile::restore_from_doublewrite(): Choose the latest applicable
page from the doublewrite buffer.

recv_dblwr_t::find_page(): Also validate encrypted or
page_compressed pages.

recv_dblwr_t::validate_page(): New function to validate a page,
either a copy in a data file or in the doublewrite buffer.
Also validate encrypted or page_compressed pages.

This is joint work with Thirunarayanan Balathandayuthapani.

row_vers_impl_x_locked_low(): clust_offsets may point to memory
that is allocated by mem_heap_alloc() and may have been freed.
For initializing clust_offsets, try to use the stack-allocated
buffer instead of a pointer that may point to freed memory.

This fixes a regression that was introduced in
commit f0aa073f (MDEV-20950).

MDEV-18042 Server crashes upon adding a non-null date column under NO_ZERO_DATE with ALGORITHM=INPLACE

accept table_name and db_name instead of table_share in make_truncated_value_warning

Call mark_columns_per_binlog_row_image before find_row() to set up table->vcol_set early,
so the virtual column value will be updated after record read (ha_rnd_pos/ha_index_next/etc)
by table->update_virtual_fields() call

don't GRANT UPDATE ON mysql.global_priv TO mariadb.sys@localhost;

Classes that handle privilege tables (like Tables_priv_table)
could read some columns conditionally but they expect a certain
minimal number of colunms always to exist.

Add a check for a minimal required number of columns in privilege tables,
don't use a table that has fewer columns than required.

1. Fixing ROUND(x) and TRUNCATE(x,0) with TINYINT, SMALLINT, MEDIUMINT, BIGINT
   input to preserve the exact data type of the argument when it's possible.

2. Fixing FLOOR(x) and CEILING(x) with TINYINT, SMALLINT, MEDIUMINT, BIGINT
  to preserve the exact data type of the argument.

3. Adding dedicated Type_handler_year::Item_func_round_fix_length_and_dec()
  to easier handle ROUND(x) and TRUNCATE(x,y) for the YEAR(2) and YEAR(4)
  input. They still return INT(2) UNSIGNED and INT(4) UNSIGNED correspondingly,
  as before.

rec_get_nth_cfield(): Remove a bogus debug assertion.
The function may be invoked by innobase_rec_to_mysql()
for reporting a duplicate key error during CREATE UNIQUE INDEX
or ALTER TABLE...ADD UNIQUE KEY, and in that case the record
will be missing the 5-byte or 6-byte fixed header.

It turns out that in every other code path leading to
rec_get_nth_cfield() we either invoked rec_get_offsets()
ourselves or asserted rec_offs_validate(). So, we can
safely remove the assertion and make debug builds
smaller and faster.

Problem:
========
In row_merge_drop_indexes(), InnoDB drops only the index from
dictionary and frees the index pages but it maintains the index
object if the table is being used by other DML threads. It sets
the online status of the index to ONLINE_INDEX_ABORTED_DROPPED.
Removing the index from dictionary doesn't remove the
corressponding ahi entries of the index. When block is being
reused, InnoDB tries to remove ahi entries for the block and
it fails if index online status is ONLINE_INDEX_ABORTED_DROPPED.

Fix:
====
MDEV-22456 allows the index ahi entries to be dropped lazily.
so checking online status in btr_search_drop_page_hash_index()
is meaningless and should be removed.

Due to restricted size of the threadpool, execution of client queries can
be delayed (queued) for a while. This delay was interpreted as client
inactivity, and connection is closed, if client idle time + queue time
exceeds wait_timeout.

But users did not expect queue time to be included into wait_timeout.

This patch changes the behavior. We don't close connection anymore,
if there is some unread data present on connection,
even if wait_timeout is exceeded. Unread data means that client
was not idle, it sent a query, which we did not have time to process yet.

trx_rollback_active(), trx_rollback_resurrected(): Replace
an incorrect condition that we failed to replace in
commit b68f1d84 (MDEV-21217).

Implementing dedicated fixing methods:
- Type_handler_bit::Item_func_round_fix_length_and_dec()
- Type_handler_bit::Item_func_int_val_fix_length_and_dec()
- Type_handler_typelib::Item_func_round_fix_length_and_dec()

because the inherited methods did not work well.

Fixing:
- Type_handler_typelib::Item_func_int_val_fix_length_and_dec
  It did not work well, because it used args[0]->max_length to
  calculate the result data type. In case of ENUM and SET it was
  not correct, because in FLOOR() and CEILING() context
  ENUM and SET return not more than 5 digits (65535 is the biggest
  possible value).

Misc:
- Changing the API of
    Type_handler_bit::Bit_decimal_notation_int_digits(const Item *item)
  to a more generic form:
    Type_handler_bit::Bit_decimal_notation_int_digits_by_nbits(uint nbits)

- Fixing Type_handler_bit::Bit_decimal_notation_int_digits_by_nbits() to
  return the exact number of decimal digits for all nbits 1..64.
  The old implementation was approximate.
  This change gives better (more precise) data types.

- Type_handler_hex_hybrid did not override
  Type_handler_string_result::Item_func_round_fix_length_and_dec(),
  so the result type of ROUND(0xFFFFFFFFFFFFFFFF) was erroneously
  calculated ad DOUBLE with a wrong length.
  Overriding Item_func_round_fix_length_and_dec(), to calculated
  the result type as INT/BIGINT.

  Also, fixing Item_func_round::fix_arg_int() to use
  args[0]->decimal_precision() instead of args[0]->max_length
  when calculating this->max_length, to get a correct result
  for hex hybrids.

- Type_handler_hex_hybrid::Item_func_int_val_fix_length_and_dec()
  called item->fix_length_and_dec_int_or_decimal(), which did not
  produce a correct result data type for hex hybrid.
  Implementing a dedicated code instead, to return INT UNSIGNED or
  BIGINT UNSIGNED depending in the number of digits in the arguments.

Removing plugin from the mysql.plugin even if the plugin is not loaded

I run perf top during ./mtr testing and constantly see times()
function there. It's so slow, that it has no sense to run it
in a loop too many times.

This patch speeds up -suite=innodb for me from 218s to 208s.
9s of times() function!

MDEV-16023 Unfortunate error message WARN_VERS_PART_FULL (partition <name> is full) when rotation time for the last interval passed

* remove one case of WARN_VERS_PART_FULL

Doesn't allow instant alter of a field which is a prefix part of some key

is_part_of_a_key_prefix(): I hope the name of the function is clear

ha_innobase::can_convert_string()
ha_innobase::can_convert_varstring()
ha_innobase::can_convert_blob(): it can't when field is_part_of_a_key_prefix()