If any given variable the xtrabackup-v2 sst script looks for is specified
  multiple times in cnf file then it tend to pick both of them causing
  some of the follow-up command to fail.

  Avoid this programatic mistake by honoring only the last variable assigned
  setting as done by mysqld too.

  Check https://bugs.launchpad.net/percona-xtradb-cluster/+bug/1362830

Semantics:
---------

* Generally end-user will create a separate user with needed
privileges for
    performing DONOR action.
* This user credentials are specified using wsrep_sst_auth.

* Along with this user there could be other user(s) created on the
server
    that sysadmin may use for normal or other operations
* Credentials for these user(s) can be specified in same
cluster/server
    cnf file as part of [client] section

When cluster act as DONOR and if wsrep_sst_auth is provided then it
should
strictly use it for performing SST based action.

What if end-user has same credentials for performing both SST action
and
normal admin work ?
* Then end-user can simply specify these credentials as part of
[client]
    section in cnf file and skip providing wsrep_sst_auth.

Issue:
-----

MySQL client user/password parsing preference order is as follows:
* command line (through --user/--password)
* cnf file
* MYSQL_PWD enviornment variable.

Recent change tried passing sst user password through MYSQL_PWD
(and user though --user command line param as before).

On the system where-in admin had another user for performing non-SST
actions,
credentials for such user were present in cnf file under [client]
section.

Due to mysql client preference order, SST user name was used (as it
was
passed through command line) but password of other user (meant for
non-SST)
action was being used as it was passed through cnf file.

Password passed through MYSQL_PWD was completely ignored causing
user-name/password mismatch.

Solution:
---------

* If user has specified credentials for SST then pass them through
command
    line so that they are used in priority.

(There could be security concern on passing things through command
line but
   when I tried passing user-name and password through command line to
mysql
   client and then did ps I saw this
   ./bin/mysql --user=sstuser --password=x xxxxxxxx -S /tmp/n1.sock
so seems like password is not shown)

don't transform Item_func_nullif if it's context_analysis_only

when calculating COUNT(basic_const), take into account that
this basic_const may be NULL

This fixes
MDEV-9538 Server crashes in check_show_access on SHOW STATISTICS
MDEV-9539 Server crashes in make_columns_old_format on SHOW GEOMETRY_COLUMNS
MDEV-9540 SHOW SPATIAL_REF_SYS and SHOW SYSTEM_VARIABLES return empty results with numerous warnings

when doing set_field_to_new_field (from switch_to_nullable_trigger_fields())
make sure that the field we're about to change actually belongs
to the right table (otherwise we cannot dereference new_field[]
array as the wrong table might have more fields than
new_field[] has elements)

Case: table with a NOT NULL field, BEFORE UPDATE trigger,
and UPDATE with a subquery that uses GROUP BY on that
NOT NULL field, and needs a temporary table for it.

Because of the BEFORE trigger, the field becomes nullable
temporarily. But its Item_field (used in GROUP BY) doesn't.
When working with the temptable some code looked at
item->maybe_null, some - at field->null_ptr.
The fix: make Item_field nullable when its field is.

This triggers an assert. The group key size is calculated
before the item is made nullable, so the group key doesn't
have a null byte. The fix: make fields/items nullable
before the group key size is calculated.

when replicating old temporal type fields (that don't store
metadata in the binlog), take the precision from
destination fields.

(this fixes the replication failure, crashes were
fixed in a different commit)

it's *display length* (a.k.a. field_length)
not storage length (a.k.a. pack_length)

* make a local variable for target_table->field[col]
* move an often-used bit function to my_bit.h
* remove a non-static and not really needed trivial comparison
  function with a very generic name

to avoid run-time libjemalloc.so dependency
link binary tarballs with a static libjemalloc_pic.a

- test for FLUSH TABLES hang in slave node

- avoiding the race condition, by not grabbing thd->LOCK_wsrep_thd for
  accessing thd->wsrep_exec_mode. The caller is same thread and exec mode
  can only be changed by self.

- added mtr test case for this issue
- not a perfect one, depends on some sleeps instead of checking
  if sync points are met

- added dbug sync points for further mtr test for this issue

- Add calls to wsrep_sync_wait for
  SHOW CREATE DB/PROCEDURE/FUNCTION/TRIGGER/EVENT
  and SHOW PROCEDURE/FUNCTION CODE

Galera MTR Tests: adjust the galera.galera_defaults test for the new MTR default value for repl.causal_read_timeout

Fix remaining issues with wsrep_sync_wait and query cache.

- Fixes misplaced call to invalidate query cache in
  Rows_log_event::do_apply_event().
  Query cache was invalidated too early, and allowed old
  entries to be inserted to the cache.

- Reset thd->wsrep_sync_wait_gtid on query cache hit.
  THD->cleanup_after_query is not called in such cases,
  and thd->wsrep_sync_wait_gtid remained initialized.

Restore tests for FLUSH commands supported by MariaDB.

* Total order isolation was started twice for FLUSH TABLES, from
  reload_acl_and_cache() and from mysql_execute_command(). Removed
  the reload_acl_and_cache() part.
* Removed PXC specific stuff from MTR tests

- Eliminates code duplication in query cache patch
- Reduces the number of iterations in mysql-wsrep#201.test
  to shorten the execution time
- Adds a new test case that exercises more scenarios

- Restore FLUSH commands supported by MariaDB (removed in
the previous commit)
- Adjust test case