Allocate password hash in statment memory

        Item_func_json_length fixed.

        Array counter didn't increment after an item was found.

fil_tablespace_iterate(): Call fil_space_destroy_crypt_data() to
invoke mutex_free() for the mutex_create() that was done in
fil_space_read_crypt_data(). Also, remember to free
iter.crypt_io_buffer.

The failure to call mutex_free() would cause sync_latch_meta_destroy()
to access freed memory on shutdown. This affected the IMPORT of
encrypted tablespaces.

Copy and adapt the test from MySQL 5.7.17.

fil_space_crypt_cleanup(): Call mutex_free() to pair with
fil_space_crypt_init().

fil_space_destroy_crypt_data(): Call mutex_free() to pair with
fil_space_create_crypt_data() and fil_space_read_crypt_data().

fil_crypt_threads_cleanup(): Call mutex_free() to pair with
fil_crypt_threads_init().

fil_space_free_low(): Invoke fil_space_destroy_crypt_data().

fil_close(): Invoke fil_space_crypt_cleanup(), just like
fil_init() invoked fil_space_crypt_init().

Datafile::shutdown(): Set m_crypt_info=NULL without dereferencing
the pointer. The object will be freed along with the fil_space_t
in fil_space_free_low().
Remove some unnecessary conditions (ut_free(NULL) is OK).

srv_shutdown_all_bg_threads(): Shut down the encryption threads
by calling fil_crypt_threads_end().

srv_shutdown_bg_undo_sources(): Do not prematurely call
fil_crypt_threads_end(). Many pages can still be written by
change buffer merge, rollback of incomplete transactions, and
purge, especially in slow shutdown (innodb_fast_shutdown=0).

innobase_shutdown_for_mysql(): Call fil_crypt_threads_cleanup()
also when innodb_read_only=1, because the threads will have been
created also in that case.

sync_check_close(): Re-enable the invocation of sync_latch_meta_destroy()
to free the mutex list.

Merged fix for innodb_mysql from 5.7.

Implementation of MDEV-7660 introduced unwanted incompatible change:
modifications under LOCK TABLES with autocommit enabled are rolled back on
disconnect. Previously everything was committed, because LOCK TABLES didn't
adjust autocommit setting.

This patch restores original behavior by reverting some changes done in
MDEV-7660:
- sql/sql_parse.cc: do not reset autocommit on LOCK TABLES
- sql/sql_base.cc: do not set autocommit on UNLOCK TABLES
- test cases: main.lock_tables_lost_commit, main.partition_explicit_prune,
  rpl.rpl_switch_stm_row_mixed, tokudb.nested_txn_implicit_commit,
  tokudb_bugs.db806

But it makes InnoDB tables under LOCK TABLES ... READ [LOCAL] not protected
against DML. To restore protection some changes from WL#6671 were merged,
specifically MDL_SHARED_READ_ONLY and test cases.

WL#6671 merge highlights:
- Not all tests merged.
- In MySQL LOCK TABLES ... READ acquires MDL_SHARED_READ_ONLY for all engines,
  in MariaDB MDL_SHARED_READ is always acquired first and then upgraded to
  MDL_SHARED_READ_ONLY for InnoDB only.
- The above allows us to omit MDL_SHARED_WRITE_LOW_PRIO implementation in
  MariaDB, which is rather useless with InnoDB. In MySQL it is needed to
  preserve locking behavior between low priority writes and LOCK TABLES ... READ
  for non-InnoDB engines (covered by sys_vars.sql_low_priority_updates_func).
- Omitted HA_NO_READ_LOCAL_LOCK, we rely on lock_count() instead.
- Omitted "piglets": in MariaDB stream of DML against InnoDB table may lead to
  concurrent LOCK TABLES ... READ starvation.
- HANDLER ... OPEN acquires MDL_SHARED_READ instead of MDL_SHARED in MariaDB.
- Omitted SNRW->X MDL lock upgrade for IMPORT/DISCARD TABLESPAECE under LOCK
  TABLES.
- Omitted strong locks for views, triggers and SP under LOCK TABLES.
- Omitted IX schema lock for LOCK TABLES READ.
- Omitted deadlock weight juggling for LOCK TABLES.

Full WL#6671 merge status:
- innodb.innodb-lock: fully merged
- main.alter_table: not merged due to different HANDLER solution
- main.debug_sync: fully merged
- main.handler_innodb: not merged due to different HANDLER solution
- main.handler_myisam: not merged due to different HANDLER solution
- main.innodb_mysql_lock: fully merged
- main.insert_notembedded: fully merged
- main.lock: not merged (due to no strong locks for views)
- main.lock_multi: not merged
- main.lock_sync: fully merged (partially in MDEV-7660)
- main.mdl_sync: not merged
- main.partition_debug_sync: not merged due to different HANDLER solution
- main.status: fully merged
- main.view: fully merged
- perfschema.mdl_func: not merged (no such test in MariaDB)
- perfschema.table_aggregate_global_2u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_global_2u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_global_4u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_global_4u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_hist_2u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_hist_2u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_hist_4u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_hist_4u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_thread_2u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_thread_2u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_thread_4u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_aggregate_thread_4u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_global_2u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_global_2u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_global_4u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_global_4u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_hist_2u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_hist_2u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_hist_4u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_hist_4u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_thread_2u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_thread_2u_3t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_thread_4u_2t: not merged (didn't fail in MariaDB)
- perfschema.table_lock_aggregate_thread_4u_3t: not merged (didn't fail in MariaDB)
- sys_vars.sql_low_priority_updates_func: not merged
- include/thr_rwlock.h: not merged, rw_pr_lock_assert_write_owner and
  rw_pr_lock_assert_not_write_owner are macros in MariaDB
- sql/handler.h: not merged (HA_NO_READ_LOCAL_LOCK)
- sql/mdl.cc: partially merged (MDL_SHARED_READ_ONLY only)
- sql/mdl.h: partially merged (MDL_SHARED_READ_ONLY only)
- sql/lock.cc: fully merged
- sql/sp_head.cc: not merged
- sql/sp_head.h: not merged
- sql/sql_base.cc: partially merged (MDL_SHARED_READ_ONLY only)
- sql/sql_base.h: not merged
- sql/sql_class.cc: fully merged
- sql/sql_class.h: fully merged
- sql/sql_handler.cc: merged partially (different solution in MariaDB)
- sql/sql_parse.cc: partially merged, mostly omitted low priority write part
- sql/sql_reload.cc: not merged comment change
- sql/sql_table.cc: not merged SNRW->X upgrade for IMPORT/DISCARD TABLESPACE
- sql/sql_view.cc: not merged
- sql/sql_yacc.yy: not merged (MDL_SHARED_WRITE_LOW_PRIO, MDL_SHARED_READ_ONLY)
- sql/table.cc: not merged (MDL_SHARED_WRITE_LOW_PRIO)
- sql/table.h: not merged (MDL_SHARED_WRITE_LOW_PRIO)
- sql/trigger.cc: not merged
- storage/innobase/handler/ha_innodb.cc: merged store_lock()/lock_count()
  changes (in MDEV-7660), didn't merge HA_NO_READ_LOCAL_LOCK
- storage/innobase/handler/ha_innodb.h: fully merged in MDEV-7660
- storage/myisammrg/ha_myisammrg.cc: not merged comment change
- storage/perfschema/table_helper.cc: not merged (no MDL support in MariaDB PFS)
- unittest/gunit/mdl-t.cc: not merged
- unittest/gunit/mdl_sync-t.cc: not merged

MariaDB specific changes:
- handler.heap: different HANDLER solution, MDEV-7660
- handler.innodb: different HANDLER solution, MDEV-7660
- handler.interface: different HANDLER solution, MDEV-7660
- handler.myisam: different HANDLER solution, MDEV-7660
- main.mdl_sync: MDEV-7660 specific changes
- main.partition_debug_sync: removed test due to different HANDLER solution,
  MDEV-7660
- main.truncate_coverage: removed test due to different HANDLER solution,
  MDEV-7660
- mysql-test/include/mtr_warnings.sql: additional cleanup, MDEV-7660
- mysql-test/lib/v1/mtr_report.pl: additional cleanup, MDEV-7660
- plugin/metadata_lock_info/metadata_lock_info.cc: not in MySQL
- sql/sql_handler.cc: MariaDB specific fix for mysql_ha_read(), MDEV-7660

This reverts commit edf4cc75, reversing
changes made to 9320d8ae.

Try hard-coding the ID as -2 instead of -1, so that they will not
be confused with ULINT_UNDEFINED on 32-bit platforms.

The fix for bug mdev-11488 introduced the virtual method
convert_to_basic_const_item for the class Item_cache.
The implementation of this method for the class Item_cache_str
was not quite correct: the server could crash if the cached item
was null.
A similar problem could appear for the implementation of
this method for the class Item_cache_decimal. Although I could not
reproduce the problem I decided to change the code appropriately.

        JSON merging fixed.

Post-push fix: Remove the orphaned file sess0sess.h.

When a condition containing NULLIF is pushed into a materialized
view/derived table the clone of the Item_func_nullif item must
be processed in a special way to guarantee that the first argument
points to the same item as the third argument.

... galera library

Update test case.

... using TO

Fixed the 'wsrep_replicate_myisam' check to allow only limited
set of commands. Added a debug assert to discover such cases.

... with wsrep_replicate_myisam enabled

Internal updates to system statistical tables could wrongly
trigger an additional total-order replication if wsrep_repli
-cate_myisam is enabled.
Fixed by adding a check to skip total-order replication for
stat tables.

Essentially revert MDEV-6759, which addressed a double free of memory
by removing the freeing altogether, introducing the memory leaks.
No double free was observed when running the test suite -DWITH_ASAN.

Replace some mem_heap_free(foreign->heap) with dict_foreign_free(foreign)
so that the calls can be located and instrumented more easily when needed.

MySQL 5.7 supports only one shared temporary tablespace.

MariaDB 10.2 does not support any other shared InnoDB tablespaces than
the two predefined tablespaces: the persistent InnoDB system tablespace
(default file name ibdata1) and the temporary tablespace
(default file name ibtmp1).

InnoDB is unnecessarily allocating a tablespace ID for the predefined
temporary tablespace on every startup, and it is in several places
testing whether a tablespace ID matches this dynamically generated ID.

We should use a compile-time constant to reduce code size and to avoid
unnecessary updates to the DICT_HDR page at every startup.

Using a hard-coded tablespace ID will should make it easier to remove the
TEMPORARY flag from FSP_SPACE_FLAGS in MDEV-11202.

        JSON depth calculation fixed.

        String insertion fixed.

        The Item_func_json_contains_path was mistakenly set with the
        no '*' paths limitation.

MDEV-11562 Assertion `js->state == JST_VALUE' failed in check_contains(json_engine_t*, json_engine_t*).

        check_contains() fixed. When an item of an array is a complex
        structure, it can be half-read after the end of the recursive
        check_contains() call. So we just manually get to it's ending.

in slow shutdown mode don't stop purge threads until they've
purged everything there is

in slow shutdown mode stop all bg threads that might generate
new undo records to purge before stopping purge threads.

in slow shutdown mode purge threads really must exit only when there is
nothing to purge. Restore the trx_commit_disallowed check and
don't stop purge threads until all connection thread transactions
are gone.