The task deals with packing the values stored in the Unique tree for each record.

The changes brought by this feature is:

  1) Unique tree can have dynamic length keys
  2) Format of keys looks like
     <key_length> <packed_value1> <packed_value2> ....... <packed_valueN>

Unique class is currently used in

1) agg_func(DISTINCT col)
   Here most aggregate functions like SUM, AVG accept only fixed size arguments
   so it is not beneficial to use packing for these. Packing is done for
   COUNT and GROUP_CONCAT (or JSON_ARRAYAGG) aggregate function as these are meaningful

2) index-merge stores row-ids
   index merge stores row-ids which are of fixed size, so packing is not required

3) Engine Independent Table statistics
   Packing is done here for variable length data types

This task is an extension to MDEV-21580.

The parser must reject DDL operations on temporary objects when
they may modify or alter such object, including temporary tables and sequences.
The rejection is regardless (has been already in place for bin-loggable DML:s)
of the binlogging capability of the server or connection.

The patch implements the requirement. A binlog test is added.

Added a new test file for tests with delete using INNODB.

Backport this fix:
CLX-105: UPDATE query causes crash

LEX::print() should not crash when the UPDATE has no WHERE clause

Fixes CLX-373.

mtr_t::m_freed_pages: Renamed from m_freed_ranges and made it as
pointer indirection.

mtr_t::add_freed_offset(): Allocates m_freed_pages.

mtr_t:clear_freed_ranges(): Removed.

mtr_t::init(): Added debug assertion to check whether m_freed_pages
is not yet initialized.

btr_page_alloc_low(): Remove #ifdef UNIV_DEBUG_SCRUBBING.

mtr_t::commit(): Delete m_freed_pages, reset m_trim_pages and
m_freed_in_system_tablespace.

fil_space_t::clear_freed_ranges(): Added a comment to explain how
undo log tablespaces uses it.

A new state has been added to the wait condition,
which eliminates the error during the test.

Commit bf3c862f
accidentally introduced two bugs.

btr_search_update_hash_ref(): Pass the correct parameter part->heap.

btr_search_sys_t::free(): Free all memory.

Thanks to Michael Widenius and Thirunarayanan Balathandayuthapani
for pointing out these bugs.

Second attempt to fix same bug:

Use the same queue for all READ operations.
Release queues for all used pages.

This fixes a hang in the s3.alter2 test case

When converting a table (test.s3_table) from S3 to another engine, the
following will be logged to the binary log:

DROP TABLE IF EXISTS test.t1;
CREATE OR REPLACE TABLE test.t1 (...) ENGINE=new_engine
INSERT rows to test.t1 in binary-row-log-format

The bug is that the above statements are logged one by one to the binary
log. This means that a fast slave, configured to use the same S3 storage
as the master, would be able to execute the DROP and CREATE from the
binary log before the master has finished the ALTER TABLE.
In this case the slave would ignore the DROP (as it's on a S3 table) but
it will stop on CREATE of the local tale, as the table is still exists in
S3. The REPLACE part will be ignored by the slave as it can't touch the
S3 table.

The fix is to ensure that all the above statements is written to binary
log AFTER the table has been deleted from S3.

- Added missing test for binlog_filter to ALTER TABLE

- Rewrote bool Query_compressed_log_event::write() to make it more readable
  (no logic changes).
- Changed DBUG_PRINT of 'is_error:' to 'is_error():' to make it easier to
  find error: in traces.
- Ensure that 'db' is never null in Query_log_event (Simplified code).

The rw_lock_s_lock() calls for the buf_pool.page_hash became a
clear bottleneck after MDEV-15053 reduced the contention on
buf_pool.mutex. We will replace that use of rw_lock_t with a
special implementation that is optimized for memory bus traffic.

The hash_table_locks instrumentation will be removed.

buf_pool_t::page_hash: Use a special implementation whose API is
compatible with hash_table_t, and store the custom rw-locks
directly in buf_pool.page_hash.array, intentionally sharing
cache lines with the hash table pointers.

rw_lock: A low-level rw-lock implementation based on std::atomic<uint32_t>
where read_trylock() becomes a simple fetch_add(1).

buf_pool_t::page_hash_latch: The special of rw_lock for the page_hash.

buf_pool_t::page_hash_latch::read_lock(): Assert that buf_pool.mutex
is not being held by the caller.

buf_pool_t::page_hash_latch::write_lock() may be called while not holding
buf_pool.mutex. buf_pool_t::watch_set() is such a caller.

buf_pool_t::page_hash_latch::read_lock_wait(),
page_hash_latch::write_lock_wait(): The spin loops.
These will obey the global parameters innodb_sync_spin_loops and
innodb_sync_spin_wait_delay.

buf_pool_t::freed_page_hash: A singly linked list of copies of
buf_pool.page_hash that ever existed. The fact that we never
free any buf_pool.page_hash.array guarantees that all
page_hash_latch that ever existed will remain valid until shutdown.

buf_pool_t::resize_hash(): Replaces buf_pool_resize_hash().
Prepend a shallow copy of the old page_hash to freed_page_hash.

buf_pool_t::page_hash_table::n_cells: Declare as Atomic_relaxed.

buf_pool_t::page_hash_table::lock(): Explain what prevents a
race condition with buf_pool_t::resize_hash().

hash_get_n_cells(): Remove. Access n_cells directly.

hash_get_nth_cell(): Remove. Access array directly.

hash_table_clear(): Replaced with hash_table_t::clear().

hash_table_create(), hash_table_free(): Remove.

hash0hash.cc: Remove.

btr_search_sys::parts[]: A single structure for the partitions of
the adaptive hash index. Replaces the 3 separate arrays:
btr_search_latches[], btr_search_sys->hash_tables,
btr_search_sys->hash_tables[i]->heap.

hash_table_t::heap, hash_table_t::adaptive: Remove.

ha0ha.cc: Remove. Move all code to btr0sea.cc.

HASH_TABLE_SYNC_MUTEX was kind-of used for the adaptive hash index,
even though that hash table is already protected by btr_search_latches[].

HASH_TABLE_SYNC_RWLOCK was only being used for buf_pool.page_hash.
It is cleaner to decouple that synchronization from hash_table_t,
and move it to the actual user.

buf_pool_t::page_hash_latches[]: Synchronization for buf_pool.page_hash.

LATCH_ID_HASH_TABLE_MUTEX: Remove.

hash_table_t::sync_obj, hash_table_t::n_sync_obj: Remove.

hash_table_t::type, hash_table_sync_t: Remove.

HASH_ASSERT_OWN(), hash_get_mutex(), hash_get_nth_mutex(): Remove.

ib_recreate(): Merge to the only caller, buf_pool_resize_hash().

ib_create(): Merge to the callers.

ha_clear(): Merge to the only caller buf_pool_t::close().

buf_pool_t::create(): Merge the ib_create() and
hash_create_sync_obj() invocations.

ha_insert_for_fold_func(): Clarify an assertion.

buf_pool_t::page_hash_lock(): Simplify the logic.

hash_assert_can_search(), hash_assert_can_modify(): Remove.
These predicates were only being invoked for the adaptive hash index,
while they only are effective for buf_pool.page_hash.

HASH_DELETE_AND_COMPACT(): Merge to ha_delete_hash_node().

hash_get_sync_obj_index(): Remove.

hash_table_t::heaps[], hash_get_nth_heap(): Remove. It was actually unused!

hash_get_heap(): Remove. It was only used in ha_delete_hash_node(),
where we always use hash_table_t::heap.

hash_table_t::calc_hash(): Replaces hash_calc_hash().

MRI scripts cannot handle + in paths, and ubuntu CI makes use of
these.

So we remove the top level build dir from the script and
transform it into a relative path script.

Because of common dependencies between the
static libraries list can contain duplicates.

We reduce these down to the single last one in
the list.

This reduces the relative time of a rebuild from:

$ (cd builddir/; time make -j)
...
real	0m30.789s
user	1m33.477s
sys	0m19.678s

and the LIB entries
$ grep ADDLIB builddir/libmysqld/mysqlserver-\$\<CONFIG\>.mri.tpl  | wc -l
179

$ du -h builddir/libmysqld/libmariadbd.a
4.1G	builddir/libmysqld/libmariadbd.a

To:

$ (cd builddir/; time make -j)
...
real	0m20.139s
user	1m32.423s
sys	0m12.208s

$ grep ADDLIB builddir/libmysqld/mysqlserver-\$\<CONFIG\>.mri.tpl  | wc -l
25

$ du -h builddir/libmysqld/libmariadbd.a
688M	builddir/libmysqld/libmariadbd.a

from configuration files

Post-push fix: add mysqd options in backup string in mariabackup sst
script for the case of logging not in syslog.

The test mariabackup.mdev-14447 started failing due to the option
--apply-log-only that became invalid since
commit 9bdf35e9
and had been removed in
commit 8c71c6aa.

and put them all together in mysqld.cc