dict_stats_update_if_needed(): Replace the parameter THD*
with const trx_t& so that trx_t::is_wsrep() can be invoked
instead of the more expensive wsrep_on().

Replace also other occurrences of wsrep_on() with trx_t::is_wsrep().

The function wsrep_on() was being called rather frequently
in InnoDB and XtraDB. Let us cache it in trx_t and invoke
trx_t::is_wsrep() instead.

innobase_trx_init(): Cache trx->wsrep = wsrep_on(thd).

ha_innobase::write_row(): Replace many repeated calls to current_thd,
and test the cheapest condition first.

when opening the `user` table separately, reset `thd->open_tables`
for the duration of open, otherwise auto-repair fallback-and-retry
will close *all* tables (but reopen only `user`)

only use auth1 update (no "auth_or":[]) array, if there was no
"auth_or" array in the json yet.

support upgrades from 5.2 privilege tables

revert/simplify f5390eea

remove galera-specific checks from mtr and the main suite

fix embedded innodb_plugin tests

followup for 7198c6ab

Backport INSALL_SYMLINK cmake macro from 10.3.
It'll make libmysqlclient_r.* symlinks to link to the actual
shared library file, not to another symlink.

As a bonus it'll fix cmake warning about deprecated LOCATION property

This is a backport of the applicable part of
commit 93475aff and
commit 2c39f69d
from 10.4.

Before 10.4 and Galera 4, WSREP_ON is a macro that points to
a global Boolean variable, so it is not that expensive to
evaluate, but we will add an unlikely() hint around it.

WSREP_ON_NEW: Remove. This macro was introduced in
commit c863159c
when reverting WSREP_ON to its previous definition.

We replace some use of WSREP_ON with WSREP(thd), like it was done
in 93475aff. Note: the macro
WSREP() in 10.1 is equivalent to WSREP_NNULL() in 10.4.

Item_func_rand::seed_random(): Avoid invoking current_thd
when WSREP is not enabled.

_ma_fetch_keypage(): Correct an assertion that used to always hold.
Thanks to clang -Wint-in-bool-context for flagging this.

double_to_datetime_with_warn(): Suppress -Wimplicit-int-float-conversion
by adding a cast. LONGLONG_MAX converted to double will actually be
LONGLONG_MAX+1.

Since commit 7198c6ab
the ./mtr --embedded tests would fail to start innodb_plugin
because of an undefined reference to the symbol wsrep_log().

Let us define a stub for that function. The embedded server
is never built WITH_WSREP, but there are no separate storage
engine builds for the embedded server. Hence, by default,
the dynamic InnoDB storage engine plugin would be built WITH_WSREP
and it would fail to load into the embedded server library due to
a reference to the undefined symbol.

MDEV-18286 Assertion `pagecache->cnt_for_resize_op == 0' failed in
check_pagecache_is_cleaned_up on server shutdown

The reason for the crash is that the counter-of-pinned-pages in the
Aria pagecache goes wrong.
This only affects debug builds, as in these we do an assert on shutdown
if the counter-of-pinned-pages is not 0 (some page was left pinned).

The bug was that in 2 places in the page cache, when not succeeding to
pin a page and a retry was made, the counter-of-pinned-pages counter was
not properly adjusted.

In the given test case, BLOCK_COMMIT flushed all Aria files. If a block was flushed at the same time the insert tried to access it, the insert would retry to get the block and that would cause the counter to go wrong.

read TLS with my_thread_var
write TLS with set_mysys_var()

my_thread_var is no longer __attribute__ ((const)): this attribute
is simply incorrect here. Read gcc manual for more information.
sql/threadpool_generic.cc fails with that attribute.

The reason why we have wsrep_on() at all is that the macro WSREP(thd)
depends on the definition of THD, and that is intentionally an opaque
data type for InnoDB. So, we cannot avoid invoking wsrep_on(), but
we can evaluate the less expensive conditions thd && WSREP_ON before
calling the function.

Global_read_lock: Use WSREP_NNULL(thd) instead of wsrep_on(thd)
because we not only know the definition of THD but also that
the pointer is not null.

wsrep_open(): Use WSREP(thd) instead of wsrep_on(thd).

InnoDB: Replace thd && wsrep_on(thd) with wsrep_on(thd), now that
the condition has been merged to the definition of the macro
wsrep_on().

If the server is compiled WITH_WSREP=OFF, we should avoid evaluating
conditions on a global variable that is constant.

WSREP_ON_: Renamed from WSREP_ON. Defined only WITH_WSREP=ON.

WSREP_ON: Defined as unlikely(WSREP_ON_).

wsrep_on(): Defined as WSREP_ON && wsrep_service->wsrep_on_func().

The reason why we have wsrep_on() at all is that the macro WSREP(thd)
depends on the definition of THD, and that is intentionally an opaque
data type for InnoDB. So, we cannot avoid invoking wsrep_on(), but
we can evaluate the less expensive condition WSREP_ON before calling
the function.

Replaced WSREP_ON macro by single global variable WSREP_ON
that is then updated at server statup and on wsrep_on and
wsrep_provider update functions.

row_vers_vc_matches_cluster(): Remove the parameter in_purge,
which was always passed as in_purge=true.

This parameter became constant in
mysql/mysql-server@1dec14d346ac55fe72989dccb071f84b3b0d3bd6
and it always was constant in MariaDB starting from the
introduction of the function in
commit 2e814d47 (MariaDB 10.2.2).

row_prebuilt_free(): Do not attempt to drop orphan indexes
that might have been left behind by a failed ADD UNIQUE INDEX.
This avoids the execution of unwanted transactions during shutdown.

This is not crtitical as if Aria doesn't start, the server will exit at once.

The bug was that the script tried to start mysqld while there was already
a running mysqld server. Fixed by killing the running one.

mysqld_exit(): Change the assertion failure on
global_status_var.global_memory_used == 0
to fprintf, like in 0bcb65d3

It appears that in some cases, that variable may be nonzero
even when LeakSanitizer (WITH_ASAN) would not report errors.
This was observed in 10.4 88cf6f1c
with the MDEV-22348 test case (Aria startup failure when running
main.default_storage_engine).

Fix a test result.

Test do we have galera debug library with debug_sync functionality
needs to be earlier.

Also add a check for tmp file being empty and bail out with a clear
error message in such a case, as mysqld_safe prevents normal stderr
from being displayed anywhere and would fail silently on this.

MDEV-22181 : galera.galera_sst_mysqldump_with_key MTR failed: INSERT failed: 1146: Table 'test.t1' doesn't exist

Add wait condition to make sure table test.t1 is replicated
to node_2 before we insert to it.

config.

The solution is to read the system variable value on startup and to fill
databases_exclude_hash.

xb_load_list_string() became non-static and was reformatted. The system
variable value is read and processed in get_mysql_vars(), which was also
reformatted.