After MDEV-15053, MDEV-22871, MDEV-23399 shifted the scalability
bottleneck, log checkpoints became a new bottleneck.

If innodb_io_capacity is set low or innodb_max_dirty_pct_lwm is
set high and the workload fits in the buffer pool, the page cleaner
thread will perform very little flushing. When we reach the capacity
of the circular redo log file ib_logfile0 and must initiate a checkpoint,
some 'furious flushing' will be necessary. (If innodb_flush_sync=OFF,
then flushing would continue at the innodb_io_capacity rate, and
writers would be throttled.)

We have the best chance of advancing the checkpoint LSN immediately
after a page flush batch has been completed. Hence, it is best to
perform checkpoints after every batch in the page cleaner thread,
attempting to run once per second.

By initiating high-priority flushing in the page cleaner as early
as possible, we aim to make the throughput more stable.

The function buf_flush_wait_flushed() used to sleep for 10ms, hoping
that the page cleaner thread would do something during that time.
The observed end result was that a large number of threads that call
log_free_check() would end up sleeping while nothing useful is happening.

We will revise the design so that in the default innodb_flush_sync=ON
mode, buf_flush_wait_flushed() will wake up the page cleaner thread
to perform the necessary flushing, and it will wait for a signal from
the page cleaner thread.

If innodb_io_capacity is set to a low value (causing the page cleaner to
throttle its work), a write workload would initially perform well, until
the capacity of the circular ib_logfile0 is reached and log_free_check()
will trigger checkpoints. At that point, the extra waiting in
buf_flush_wait_flushed() will start reducing throughput.

The page cleaner thread will also initiate log checkpoints after each
buf_flush_lists() call, because that is the best point of time for
the checkpoint LSN to advance by the maximum amount.

Even in 'furious flushing' mode we invoke buf_flush_lists() with
innodb_io_capacity_max pages at a time, and at the start of each
batch (in the log_flush() callback function that runs in a separate
task) we will invoke os_aio_wait_until_no_pending_writes(). This
tweak allows the checkpoint to advance in smaller steps and
significantly reduces the maximum latency. On an Intel Optane 960
NVMe SSD on Linux, it reduced from 4.6 seconds to 74 milliseconds.
On Microsoft Windows with a slower SSD, it reduced from more than
180 seconds to 0.6 seconds.

We will make innodb_adaptive_flushing=OFF simply flush innodb_io_capacity
per second whenever the dirty proportion of buffer pool pages exceeds
innodb_max_dirty_pages_pct_lwm. For innodb_adaptive_flushing=ON we try
to make page_cleaner_flush_pages_recommendation() more consistent and
predictable: if we are below innodb_adaptive_flushing_lwm, let us flush
pages according to the return value of af_get_pct_for_dirty().

innodb_max_dirty_pages_pct_lwm: Revert the change of the default value
that was made in MDEV-23399. The value innodb_max_dirty_pages_pct_lwm=0
guarantees that a shutdown of an idle server will be fast. Users might
be surprised if normal shutdown suddenly became slower when upgrading
within a GA release series.

innodb_checkpoint_usec: Remove. The master task will no longer perform
periodic log checkpoints. It is the duty of the page cleaner thread.

log_sys.max_modified_age: Remove. The current span of the
buf_pool.flush_list expressed in LSN only matters for adaptive
flushing (outside the 'furious flushing' condition).
For the correctness of checkpoints, the only thing that matters is
the checkpoint age (log_sys.lsn - log_sys.last_checkpoint_lsn).
This run-time constant was also reported as log_max_modified_age_sync.

log_sys.max_checkpoint_age_async: Remove. This does not serve any
purpose, because the checkpoints will now be triggered by the page
cleaner thread. We will retain the log_sys.max_checkpoint_age limit
for engaging 'furious flushing'.

page_cleaner.slot: Remove. It turns out that
page_cleaner_slot.flush_list_time was duplicating
page_cleaner.slot.flush_time and page_cleaner.slot.flush_list_pass
was duplicating page_cleaner.flush_pass.
Likewise, there were some redundant monitor counters, because the
page cleaner thread no longer performs any buf_pool.LRU flushing, and
because there only is one buf_flush_page_cleaner thread.

buf_flush_sync_lsn: Protect writes by buf_pool.flush_list_mutex.

buf_pool_t::get_oldest_modification(): Add a parameter to specify the
return value when no persistent data pages are dirty. Require the
caller to hold buf_pool.flush_list_mutex.

log_buf_pool_get_oldest_modification(): Take the fall-back LSN
as a parameter. All callers will also invoke log_sys.get_lsn().

log_preflush_pool_modified_pages(): Replaced with buf_flush_wait_flushed().

buf_flush_wait_flushed(): Implement two limits. If not enough buffer pool
has been flushed, signal the page cleaner (unless innodb_flush_sync=OFF)
and wait for the page cleaner to complete. If the page cleaner
thread is not running (which can be the case durign shutdown),
initiate the flush and wait for it directly.

buf_flush_ahead(): If innodb_flush_sync=ON (the default),
submit a new buf_flush_sync_lsn target for the page cleaner
but do not wait for the flushing to finish.

log_get_capacity(), log_get_max_modified_age_async(): Remove, to make
it easier to see that af_get_pct_for_lsn() is not acquiring any mutexes.

page_cleaner_flush_pages_recommendation(): Protect all access to
buf_pool.flush_list with buf_pool.flush_list_mutex. Previously there
were some race conditions in the calculation.

buf_flush_sync_for_checkpoint(): New function to process
buf_flush_sync_lsn in the page cleaner thread. At the end of
each batch, we try to wake up any blocked buf_flush_wait_flushed().
If everything up to buf_flush_sync_lsn has been flushed, we will
reset buf_flush_sync_lsn=0. The page cleaner thread will keep
'furious flushing' until the limit is reached. Any threads that
are waiting in buf_flush_wait_flushed() will be able to resume
as soon as their own limit has been satisfied.

buf_flush_page_cleaner: Prioritize buf_flush_sync_lsn and do not
sleep as long as it is set. Do not update any page_cleaner statistics
for this special mode of operation. In the normal mode
(buf_flush_sync_lsn is not set for innodb_flush_sync=ON),
try to wake up once per second. No longer check whether
srv_inc_activity_count() has been called. After each batch,
try to perform a log checkpoint, because the best chances for
the checkpoint LSN to advance by the maximum amount are upon
completing a flushing batch.

log_t: Move buf_free, max_buf_free possibly to the same cache line
with log_sys.mutex.

log_margin_checkpoint_age(): Simplify the logic, and replace
a 0.1-second sleep with a call to buf_flush_wait_flushed() to
initiate flushing. Moved to the same compilation unit
with the only caller.

log_close(): Clean up the calculations. (Should be no functional
change.) Return whether flush-ahead is needed. Moved to the same
compilation unit with the only caller.

mtr_t::finish_write(): Return whether flush-ahead is needed.

mtr_t::commit(): Invoke buf_flush_ahead() when needed. Let us avoid
external calls in mtr_t::commit() and make the logic easier to follow
by having related code in a single compilation unit. Also, we will
invoke srv_stats.log_write_requests.inc() only once per
mini-transaction commit, while not holding mutexes.

log_checkpoint_margin(): Only care about log_sys.max_checkpoint_age.
Upon reaching log_sys.max_checkpoint_age where we must wait to prevent
the log from getting corrupted, let us wait for at most 1MiB of LSN
at a time, before rechecking the condition. This should allow writers
to proceed even if the redo log capacity has been reached and
'furious flushing' is in progress. We no longer care about
log_sys.max_modified_age_sync or log_sys.max_modified_age_async.
The log_sys.max_modified_age_sync could be a relic from the time when
there was a srv_master_thread that wrote dirty pages to data files.
Also, we no longer have any log_sys.max_checkpoint_age_async limit,
because log checkpoints will now be triggered by the page cleaner
thread upon completing buf_flush_lists().

log_set_capacity(): Simplify the calculations of the limit
(no functional change).

log_checkpoint_low(): Split from log_checkpoint(). Moved to the
same compilation unit with the caller.

log_make_checkpoint(): Only wait for everything to be flushed until
the current LSN.

create_log_file(): After checkpoint, invoke log_write_up_to()
to ensure that the FILE_CHECKPOINT record has been written.
This avoids ut_ad(!srv_log_file_created) in create_log_file_rename().

srv_start(): Do not call recv_recovery_from_checkpoint_start()
if the log has just been created. Set fil_system.space_id_reuse_warned
before dict_boot() has been executed, and clear it after recovery
has finished.

dict_boot(): Initialize fil_system.max_assigned_id.

srv_check_activity(): Remove. The activity count is counting transaction
commits and therefore mostly interesting for the purge of history.

BtrBulk::insert(): Do not explicitly wake up the page cleaner,
but do invoke srv_inc_activity_count(), because that counter is
still being used in buf_load_throttle_if_needed() for some
heuristics. (It might be cleaner to execute buf_load() in the
page cleaner thread!)

Reviewed by: Vladislav Vaintroub

buf_flush_remove_pages(), buf_flush_dirty_pages(): Because
buf_page_t::state() is protected by buf_pool.mutex, which we
are not holding, the state may be BUF_BLOCK_REMOVE_HASH when
the page is being relocated. Let us relax these assertions
similar to buf_flush_validate_low().

The other in_file() assertions in buf0flu.cc look valid.

srv_start(): Avoid trx_lists_init_at_db_start() for normal
mariabackup --prepare without --export.

innodb_preshutdown(): Terminate the encryption threads before
the page cleaner thread can be shut down.

innodb_shutdown(): Always wait for the encryption threads and
page cleaner to shut down.

srv_shutdown_all_bg_threads(): Wait for the encryption threads and
the page cleaner to shut down. (After an aborted startup,
innodb_shutdown() would not be called.)

row_get_background_drop_list_len_low(): Remove.

os_thread_count: Remove. Alternatively, at the end of
srv_shutdown_all_bg_threads() we could try to wait longer
for the count to reach 0. On some platforms, an assertion
os_thread_count==0 could fail even after a small delay,
even though in the core dump all threads would have exited.

srv_shutdown_threads(): Renamed from srv_shutdown_all_bg_threads().
Do not wait for the page cleaner to shut down, because the later
innodb_shutdown(), which may invoke
logs_empty_and_mark_files_at_shutdown(), assumes that it exists.

storage engines are generally initialized in some random order
(by iterating the hash of plugin names).

S3 fails if it's initialized before Aria.

But it looks that while S3 needs Aria, it does not need
Aria to be initialized before S3. S3 copies maria_hton and then
overwrites every single member of it, so it can handle Aria being
initialized after S3.

fix TokuDB to compile with the perfschema

view_pseudo_hton cannot be dereferenced

first try to resolve the function name as a native function,
and only then look within pluggable data types

Fix the Item_func_json_objectagg::fix_fields to save the orig_args.

Ubuntu Xenial

Fixes 7f613ebd (MDEV-7284 INDEX: CREATE OR REPLACE).

We must make the test depend on a debug version of Galera.

In commit 7eda5561 we removed a
valid debug assertion.

AddressSanitizer would trip when writing undo log for an INSERT
operation that follows the problematic ALTER TABLE because the
v_indexes would refer to an index object that was freed during
the execution of ALTER TABLE.

The operation to remove NOT NULL attribute from a column should
lead into any affected indexes to be dropped and re-created.
But, the SQL layer set the ha_alter_info->handler_flags to
HA_INPLACE_ADD_UNIQUE_INDEX_NO_WRITE|ALTER_COLUMN_NULLABLE
(that is, InnoDB was asked to add an index and change the column,
but not to drop the index that depended on the column).

Let us restore the debug assertion that catches this problem
outside AddressSanitizer, and 'defuse' the offending ALTER TABLE
statement in the test until something has been fixed in the SQL layer.

MDEV-23935: Fix warnings generated during compilation of plugin/auth_pam/testing/pam_mariadb_mtr.c on MacOS

During build server 10.4 on MacOS warnings like the following one
are generated on compiling the file plugin/auth_pam/testing/pam_mariadb_mtr.c

server-10.4/plugin/auth_pam/testing/pam_mariadb_mtr.c:25:22: error:
initializing 'char *' with an expression of type 'const char [23]'
discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
{ PAM_TEXT_INFO, "Challenge input first." }

The reason of the warnings is that the data member pam_message::msg is declared
as 'char *' on MacOS but initializer of the data member is 'const char *'.

To eliminate warnings the compiler option
  -Wno-incompatible-pointer-types-discards-qualifiers
has been added to the compiler flags used for compiling the file
pam_mariadb_mtr.c.

MDEV-20945: BACKUP UNLOCK + FTWRL assertion failure | SIGSEGV in I_P_List
from MDL_context::release_lock on INSERT w/ BACKUP LOCK (on optimized
builds) | Assertion `ticket->m_duration == MDL_EXPLICIT' failed

BACKUP LOCK behavior is modified so it won't be used wrong:
- BACKUP LOCK should commit any active transactions.
- BACKUP LOCK should not be allowed in stored procedures.
- When BACKUP LOCK is active, don't allow any DDL's for that connection.
- FTWRL is forbidden on the same connection while BACKUP LOCK is active.

Reviewed-by: monty@mariadb.com

Some functions on ha_partition call functions on all partitions, but handler->reset() is only called that pruned by m_partitions_to_reset. So Spider didn't clear pointer on unpruned partitions, if the unpruned partitions are used by next query, Spider reference the pointer that is already freed.

Some functions on ha_partition call functions on all partitions, but handler->reset() is only called that pruned by m_partitions_to_reset. So Spider didn't clear pointer on unpruned partitions, if the unpruned partitions are used by next query, Spider reference the pointer that is already freed.

Change xarecover_handlerton so that transaction with WSREP prefixed
xids are rolled back when Galera is disabled.
Reviewd-by: Jan Lindström <jan.lindstrom@mariadb.com>

Compiler warnings like one listed below are generated during server build on MacOS:
In file included from server-10.2-MDEV-23564/mysys_ssl/openssl.c:33:
In file included from /usr/local/include/openssl/evp.h:16:
In file included from /usr/local/include/openssl/bio.h:20:
/usr/local/include/openssl/crypto.h:206:10: warning: 'CRYPTO_cleanup_all_ex_data' macro redefined [-Wmacro-redefined]
           ^
  /mariadb/server-10.2-MDEV-23564/include/ssl_compat.h:46:9: note: previous definition is here
          ^

In case MariaDB serer is build with -DCMAKE_BUILD_TYPE=Debug it results in
build error.

The reason of compiler warnings is that header file <ssl_compat.h>
included before the openssl system header files. File ssl_compat.h
contains some macros with the same names as SSL API functions declared
in the openssl system header files. It resulted in duplicate
symbols that produces compiler warnings.

To fix the issue the header file ssl_compat.h should be included
after a line where openssl system header is included.

It was only from CMake-3.14.0 that CMAKE_REQUIRED_LINK_OPTIONS
was used in CHECK_CXX_SOURCE_COMPILES. Without this, it could be
the case (as was on OSX) that a flag was never checked in
CHECK_CXX_SOURCE_COMPILES, the CHECK successfully passed, but
failed at link time.

As such we use CMAKE_REQUIRED_LIBRARIES to include the flags to check
as its compatible enough with the cmake versions for non-Windows
compilers/linkers.

Tested on x86_64 with:
* 3.11.4
* 3.17.4

Corrects: 7473e184

In the future:
* cmake >=3.14.0 can use CMAKE_REQUIRED_LINK_OPTIONS
* cmake >=3.18.0 can use CHECK_LINKER_FLAG (with policy CMP0057 NEW)
(e.g: commit c7ac2deff9a2c965887dcc67cbf2a3a7c3e0123d)

CMAKE_REQUIRED_LIBRARIES suggested by serg@mariadb.com

Reviewed-by: anel@mariadb.org

MDEV-22871 tried to optimize the buf_page_t initialization in
buf_page_init_for_read() by initializing everything while the block
is in freed state, and only afterwards attaching the block to
buf_pool.page_hash.

In an rr replay trace, we have multiple threads executing in
buf_page_optimistic_get() on the same buf_block_t while the block is
being freed and reallocated several times in buf_page_init_for_read().
Because also the buf_page_t::id() is changing, the buf_pool.page_hash
is being protected by a different rw-lock than the one that
buf_page_optimistic_get() are successfully read-locking.

buf_page_optimistic_get(): Validate also buf_page_t::id() after
acquiring the buf_pool.page_hash latch.

Reviewed by: Thirunarayanan Balathandayuthapani

In MDEV-12353, we changed the redo log format so that whenever
any data field is changed, the unchanged prefix of the bytes
will by default be omitted from the redo log record.

However, in order for the MDEV-23199 logic to work, changes of
FSP_SPACE_FLAGS must always be written in full (mtr_t::FORCED),
so that crash recovery can parse them. We must know the flags
in advance, because we might be applying log to other pages than
page 0 first.

recv_scan_log_recs(): Correct a misleading message about starting
crash recovery. Display both the checkpoint LSN and the start
of the records that end in the FILE_CHECKPOINT marker.

Reviewed by: Thirunarayanan Balathandayuthapani

The only applicable InnoDB change to MariaDB that was made
between MySQL 5.6.49 and MySQL 5.6.50 is MDEV-23999.

fts_query_t::nested_sub_exp: Keep track of nested
fts_ast_visit_sub_exp() calls.

fts_ast_visit_sub_exp(): Return DB_OUT_OF_MEMORY if the
maximum recursion depth is exceeded.

This is motivated by a change in MySQL 5.6.50:
mysql/mysql-server@e2a46b4834a0030e5380d45789772cb6beab6e92
Bug #29929684 USING MANY NESTED ARGUMENTS WITH BOOLEAN FTS CAN LEAD
TO TERMINATE SERVER

Updated submodule libmarias3 which fixes the problem
Enabled disable S3 tests.

- Indentation changes
- Fixed wrong name for used in DBUG_ENTER
- Added some code comments

This failure was caused because of several bugs:
- Someone had removed s3-slave-ignore-updates=1 from slave.cnf, which
  caused the slave to remove files that the master was working on.
- Bug in ha_partition::change_partitions() that didn't reset m_new_file
  in case of errors. This caused crashes in ha_maria::extra() as the
  maria handler was called on files that was already closed.
- In ma_pagecache there was a bug that when one got a read error one a
  big block (s3 block), it left the flag PCBLOCK_BIG_READ on for the page
  which cased an assert when the page where flushed.
- Flush all cached tables in case of ignored ALTER TABLE

Note that when merging code from 10.3, that fixes the partition bug, use
the code from this patch instead.

Changes to ma_pagecache.cc written or reviewed by Sanja

This commit fixed the problems with S3 after the "DROP TABLE FORCE" changes.
It also fixes all failing replication S3 tests.

A slave is delayed if it is trying to execute replicated queries on a
table that is already converted to S3 by the master later in the binlog.

Fixes for replication events on S3 tables for delayed slaves:
- INSERT and INSERT ... SELECT and CREATE TABLE are ignored but written
  to the binary log.   UPDATE & DELETE will be fixed in a future commit.

Other things:
- On slaves with --s3-slave-ignore-updates set, allow S3 tables to be
  opened in read-write mode. This was done to be able to
  ignore-but-replicate queries like insert.  Without this change any
  open of an S3 table failed with 'Table is read only' which is too
  early to be able to replicate the original query.
- Errors are now printed if handler::extra() call fails in
  wait_while_tables_are_used().
- Error message for row changes are changed from HA_ERR_WRONG_COMMAND
  to HA_ERR_TABLE_READONLY.
- Disable some maria_extra() calls for S3 tables. This could cause
  S3 tables to fail in some cases.
- Added missing thr_lock_delete() to ma_open() in case of failure.
- Removed from mysql_prepare_insert() the not needed argument 'table'.

Other things:
- Updated help text for --gdb