mem_heap_create_block(): Poison the payload area until
mem_heap_alloc() unpoisons it.

fil_iterate(), fil_tablespace_iterate(): Replace os_file_read()
with os_file_read_no_error_handling().

os_file_read_func(), os_file_read_no_error_handling_func():
Do not retry partial reads. There used to be an infinite amount
of retries. Because InnoDB extends both data and log files upfront,
partial reads should be impossible during normal operation.

Initialize block.page.zip only once.

PageConverter::update(): Initialize m_page_zip_ptr
as late as possible.
(We should really remove it at some point.)

PageConverter::operator(): Refer to block->page.zip instead of
m_page_zip_ptr.

AbstractCallback::get_frame(): Define static. Refer
to block->page.zip.data directly.

fil_iterate(): Refer to block->page.zip.data directly.

fil_tablespace_iterate(): Initialize block.page.zip.data as soon
as possible.

fil_iterate(): Validate the pages directly.

import_page_status_t, PageConverter::validate(): Remove.

AbstractCallback::filename(): New accessor.

AbstractCallback::is_interrupted(): Replaces periodic_check().

PageConverter::trigger_corruption(): Remove.

Reduce unnecessary inter-module calls for IMPORT TABLESPACE.
Move some IMPORT-related code from fil0fil.cc to row0import.cc.

PageCallback: Remove. Make AbstractCallback the base class.

PageConverter: Define some member functions inline.

		assert on UTF-8 columns

Problem:
=======
(1) Multi-byte character cases are not considered during prefix index
cluster optimization check. It leads to fetch of improper results during
read operation.
(2) Strict assert in row_sel_field_store_in_mysql_format_func and it asserts
for prefix index record to mysql conversion.

Solution:
========
(1) Consider the case of multi-byte character during prefix index
cluster optimization check.
(2) Relax the assert in row_sel_field_store_in_mysql_format_func to allow
prefix index record to mysql format conversion.

The patch is taken from
https://github.com/laurynas-biveinis/percona-server/commit/1eee538087ffcf121c37f844b447ba5480faf081

Refs: MW-245 - changed logic so that in non primary node it is possible to do SET + SHOW + SELECT from information and pfs schema, when dirty reads are not enabled - however, non table selects are not allowed (e.g. SELECT 1)

Refs MW-245 - logic was wrong in detecting if queries are allowed in non primary node. it allowed select with no table list to execute even if dirty reads was not specified

refs MW-245 - allowing USE <database> with dirty reads configuration - fix for logic of setting wsrep ready status

MDEV-12737: tokudb_mariadb.mdev6657 fails in buildbot with different plan, and outside with valgrind warnings

Fixing the test by adding replace column for the rows column in the explain.

MDEV-10991: Server crashes in spider_udf_direct_sql_create_conn - tests in spider/oracle* suites crash the server

The crash occurs due to code that is #ifdef'd out with HAVE_ORACLE_OCI that
pertains to the use of Spider with an Oracle data tier. Enabling this code
eliminates the crash.

The reason that MariaDB needs to support Oracle storage at the data tier is
to help customers migrate from Oracle. It is necessary to build Spider with
the additional build flag -DHAVE_ORACLE_OCI, and install and start Oracle
before running the Oracle test suite or any tests within it. Nevertheless,
if Spider is built normally and Oracle has not been started, these tests
should not cause the MariaDB server to crash. The bug fix replaces the
crash with the following error:
  ERROR 12501 (HY000) at line 4: The connect info 'ORACLE' is invalid

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Learn both valgrind and asan to catch this bug:

  mem_heap_t* heap = mem_heap_create(1024);
  byte* p = reinterpret_cast<byte*>(heap) + sizeof(mem_heap_t);
  *p = 123;

Overflows of the last allocation in a block will be catched too.

mem_heap_create_block(): poison newly allocated memory

cmp_item_sort_string::store_value() did not cache the string returned
from item->val_str(), whose result can point to various private members
such as Item_char_typecast::tmp_value.

- cmp_item_sort_string::store_value() remembered the pointer returned
  from item->val_str() poiting to tmp_value into cmp_item_string::value_res.
- Later, cmp_item_real::store_value() was called, which called
  Item_str_func::val_real(), which called Item_char_typecast::val_str(&tmp)
  using a local stack variable "String tmp". Item_char_typecast::tmp_value
  was overwritten and become a link to "tmp":
  tmp_value.Ptr freed its own buffer and set to point to the buffer
  owned by "tmp".
- On return from Item_str_func::val_real(), "String tmp" was destructed,
  but "tmp_value" still pointed to the buffer owned by "tmp",
  So tmp_value.Ptr became invalid.
- Then cmp_item_sort_string() passed cmp_item_string::value_res to sortcmp().
  At this point, value_res still pointed to an invalid value of
  Item_char_typecast::tmp_value.

Fix:
changing cmp_item_sort_string::store_value() to force copying
to cmp_item_string::value if item->val_str(&value) returned
a different pointer (instead of &value).

Fix test failure on galera_flush_local.

Fix test failure on galera_concurrent_ctas

    Fortify wsrep_hton so that wsrep calls are not done to NULL-pointers.

MDEV-6736: Valgrind warnings 'Invalid read' in subselect_engine::calc_const_tables with SQ in WHERE and
           HAVING, ORDER BY, materialization+semijoin

During cleanup a pointer to the materialised table that was freed was not set to NULL

To disallow equality propagation for DATETIME with non-zero YYYYMMDD part we were setting null_value to true.
This caused issues when we were calculating selectivity for a condition as this returned IMPOSSIBLE WHERE.

The issue is resolved by not setting null_value to true for DATETIME with non-zero YYYYMMDD.

Eliminated last exit() call from libmysqld.

Unlike commit a54abf01 claimed,
the caller of THD::awake() may actually hold the InnoDB lock_sys->mutex.
That commit introduced a deadlock of threads in the replication slave
when running the test rpl.rpl_parallel_optimistic_nobinlog.

lock_trx_handle_wait(): Expect the callers to acquire and release
lock_sys->mutex and trx->mutex.

innobase_kill_query(): Restore the logic for conditionally acquiring
and releasing the mutexes. THD::awake() can be called from inside
InnoDB while holding one or both mutexes, via thd_report_wait_for() and
via wsrep_innobase_kill_one_trx().

ha_innobase::unlock_row(): Use a relaxed version of the
trx_state_eq() debug assertion, because rr_unlock_row()
may be invoked after an error has been already reported
and the transaction has been rolled back.

By definition, c_lock->trx->lock.wait_lock==c_lock cannot hold.
That is, the owner transaction of a lock cannot be waiting for that
particular lock. It must have been waiting for some other lock.
Remove the dead code related to that. Also, test c_lock for NULLness
only once.

The caller of THD::awake() should never hold any InnoDB mutexes,
so we can always acquire lock_sys->mutex and trx->mutex.

MDEV-13549 Fix and re-enable test galera.galera_var_slave_threads

Two changes were made to the test:

1) Suppress warning "Refusing exit for the last slave thread."
   This warning was already suppressed, but on the wrong node.

2) The test occasionally fails because it expects that the
   number of applier threads changes immediately after
   changing the value of ```variable wsrep_slave_threads```.
   Which is not true. This patch turns snippets like this:

   ```
   SET GLOBAL wsrep_slave_threads = x;
   SELECT COUNT(*) = x FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user';
   ```

   Into proper wait_conditions:

   ```
   SET GLOBAL wsrep_slave_threads = x;
   let $wait_condition = SELECT COUNT(*) = x FROM ...;
   --source include/wait_condition.inc
   ```

MDEV-14144 Fix for MTR tests complaining "Query didn't return a result set"

MDEV-13549 Fix for test galera.galera_var_max_ws_rows

MDEV-13549 Fix and re-enable MTR test galera.MW-366