Pass THD to Sort_and_group_tracker::report_sorting().
This reduces number of pthread_getspecific() calls from 292 to 290.

Pass THD to Item_field (and all derivatives) constructors.
This reduces number of pthread_getspecific() calls from 322 to 292.

Pass THD to find_all_keys() and Item_equal::Item_equal().
In MRR use table->in_use instead of current_thd.

This reduces number of pthread_getspecific() calls from 354 to 320.

Various fixes to let MariaDB compile with performance schema disabled.

Field_temporal_with_date::validate_for_get_date()
and reusing it in a few places.

Instead of asserting print informative error message to error log
and return failure from innodb_init causing the server to shutdown.

Added new dynamic configuration variable innodb_buf_dump_status_frequency
to configure how often buffer pool dump status is printed in the logs.
A number between [0, 100] that tells how oftern buffer pool dump status
in percentages should be printed. E.g. 10 means that buffer pool dump
status is printed when every 10% of number of buffer pool pages are
dumped. Default is 0 (only start and end status is printed).

Moved warning print to debug builds only because on production
these messages are unnecessary.

Follow-up patch to temporarily avoid a sporadic failure in the test
rpl.rpl_000011 due to MDEV-8301.

There is a window during thread exit where the global status is
counted incorrectly - the contribution for the exiting thread is
counted twice. The patch for MDEV-8294 made this window visible to the
test case rpl.rpl_000011, causing it to sporadically fail. Temporarily
silence this with a wait for the expected value; can be removed once
MDEV-8294 is fixed.

There were some cases where the slave SQL thread could stop without
the pool of parallel replication worker threads being correctly
de-activated.

Add log_bin_index, log_bin_basename and relay_log_basename system
variables. Also, convert relay_log_index system variable to
NO_CMD_LINE and implement --relay-log-index as a command line
option.

  MDEV-8167 XOR returns bad results for an indexed column
The bug itself was earlier fixed by one of the earlier changes.

The bug itself was earlier fixed by this patch:

commit 3709c7fc
MDEV-8222 "string_field LIKE int_const" returns a wrong result in case of UCS2
MDEV-8257 Erroneous "Impossible where" when mixing decimal comparison and LIKE

Analysis: Problem was that actual payload size (page size) after compression
was handled incorrectly on encryption. Additionally, some of the variables
were not initialized.

Fixed by encrypting/decrypting only the actual compressed page size.

MDEV-8268: InnoDB: Assertion failure in file buf0buf.cc line 5842 failing assertion ut_a(free_slot != NULL);

Analysis: Problem is that there is not enough temporary buffer slots
for pending IO requests.

Fixed by allocating same amount of temporary buffer slots as there
are max pending IO requests.

Removed memcpy's on cases when page is not encrypted and make sure
we use the correct buffer for reading/writing.

- Make ANALYZE correctly remember and report filesort() calls
- Temp.table use is collected but only basic info is reported.

MDEV-8250: InnoDB: Page compressed tables are not compressed and compressed+encrypted tables cause crash

Analysis: Problem is that both encrypted tables and compressed tables use
FIL header offset FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION to store
required metadata. Furhermore, for only compressed tables currently
code skips compression.

Fixes:
- Only encrypted pages store key_version to FIL header offset FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION,
  no need to fix
- Only compressed pages store compression algorithm to FIL header offset FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION,
  no need to fix as they have different page type FIL_PAGE_PAGE_COMPRESSED
- Compressed and encrypted pages now use a new page type FIL_PAGE_PAGE_COMPRESSED_ENCRYPTED and
  key_version is stored on FIL header offset FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION and compression
  method is stored after FIL header similar way as compressed size, so that first
  FIL_PAGE_COMPRESSED_SIZE is stored followed by FIL_PAGE_COMPRESSION_METHOD
- Fix buf_page_encrypt_before_write function to really compress pages if compression is enabled
- Fix buf_page_decrypt_after_read function to really decompress pages if compression is used
- Small style fixes

return unsigned, not signed.
return a value large enough for GCM

and don't recommend aes_ctr if it's unavailable

introduce ENCRYPTION_KEY_SYSTEM_DATA and
ENCRYPTION_KEY_TEMPORARY_DATA constants; use them everywhere.

IO_CACHE tempfiles encryption

when working with IO_CACHE's, don't access IO_CACHE::file directly

* remove unused (and not implemented) WRITE_NET type
* remove cast in my_b_write() macro. my_b_* macros are
  function-like, casts are responsibility of the caller
* replace hackish _my_b_write(info,0,0) with the explicit
  my_b_flush_io_cache() in my_b_write_byte()
* remove unused my_b_fill_cache()
* replace pbool -> my_bool
* make internal IO_CACHE functions static
* reformat comments, correct typos, remove obsolete comments (ISAM)
* assert valid cache type in init_functions()
* use IO_ROUND_DN() macro where appropriate
* remove unused DBUG_EXECUTE_IF in _my_b_cache_write()
* remove unnecessary __attribute__((unused))
* fix goto error in parse_file.cc
* remove redundant reinit_io_cache() in uniques.cc
* don't do reinit_io_cache() if the cache was not initialized
  in ma_check.c
* extract duplicate functionality from various _my_b_*_read
  functions into a common wrapper. Same for _my_b_*_write
* create _my_b_cache_write_r instead of having if's in
  _my_b_cache_write (similar to existing _my_b_cache_read and
  _my_b_cache_read_r)
* don't call mysql_file_write() from my_b_flush_io_cache(),
  call info->write_function() instead

that is, don't create a "temporary" IO_CACHE with file==-1
and manually swap it later to the valid file descriptor.

remove some 14-year old code that added support for
LOAD DATA replication to IO_CACHE:
* three callbacks, of which only two were actually used and that
  were only needed for LOAD DATA replication but were
  tested in every IO_CACHE instance
* an additional opaque void * argument in IO_CACHE, also only
  used for LOAD DATA replication, but present everywhere
* the code to close IO_CACHE prematurely in LOAD DATA to have
  these callbacks called in the correct order and a long
  comment explaining what will happen if IO_CACHE is not
  closed prematurely
* a variable to track whether IO_CACHE was closed prematurely
  (to avoid double-closing it)

perfschema after 5.6 merge depends on sql_yacc.h

To make st_select_lex::master_unit() inlinable:
- moved it's definition to sql_lex.h
- removed base class virtual master_unit() declaration since this method is
  specific to st_select_lex

Overhead change:
st_select_lex::master_unit()      0.17% -> out of radar
execute_sqlcom_select()           0.13% -> 0.12%
JOIN::save_explain_data_intern()  0.27% -> 0.23%
JOIN::optimize_inner()            0.76% -> 0.72%
JOIN::exec_inner()                0.30% -> 0.24%
JOIN::prepare()                   0.30% -> 0.29%
JOIN::optimize()                  0.05% -> 0.05%

Moved THD::set_command() definition to sql_class.h so that it can be inlined.

Overhead change:
THD::set_command        0.05% -> out of radar