Starting with commit baf276e6d4 (MDEV-19229)
the parameter innodb_undo_tablespaces can be increased from its
previous default value 0 while allowing an upgrade from old databases.
We will change the default setting to innodb_undo_tablespaces=3
so that the space occupied by possible bursts of undo log records
can be reclaimed after SET GLOBAL innodb_undo_log_truncate=ON.
We will not enable innodb_undo_log_truncate by default, because it
causes some observable performance degradation.
Special thanks to Thirunarayanan Balathandayuthapani for diagnosing
and fixing a number of bugs related to this new default setting.
Tested by: Matthias Leich, Axel Schwenke, Vladislav Vaintroub
(with both values of innodb_undo_log_truncate)
The purpose of the change buffer was to reduce random disk access,
which could be useful on rotational storage, but maybe less so on
solid-state storage.
When we wished to
(1) insert a record into a non-unique secondary index,
(2) delete-mark a secondary index record,
(3) delete a secondary index record as part of purge (but not ROLLBACK),
and the B-tree leaf page where the record belongs to is not in the buffer
pool, we inserted a record into the change buffer B-tree, indexed by
the page identifier. When the page was eventually read into the buffer
pool, we looked up the change buffer B-tree for any modifications to the
page, applied these upon the completion of the read operation. This
was called the insert buffer merge.
We remove the change buffer, because it has been the source of
various hard-to-reproduce corruption bugs, including those fixed in
commit 5b9ee8d819 and
commit 165564d3c3 but not limited to them.
A downgrade will fail with a clear message starting with
commit db14eb16f9 (MDEV-30106).
buf_page_t::state: Merge IBUF_EXIST to UNFIXED and
WRITE_FIX_IBUF to WRITE_FIX.
buf_pool_t::watch[]: Remove.
trx_t: Move isolation_level, check_foreigns, check_unique_secondary,
bulk_insert into the same bit-field. The only purpose of
trx_t::check_unique_secondary is to enable bulk insert into an
empty table. It no longer enables insert buffering for UNIQUE INDEX.
btr_cur_t::thr: Remove. This field was originally needed for change
buffering. Later, its use was extended to cover SPATIAL INDEX.
Much of the time, rtr_info::thr holds this field. When it does not,
we will add parameters to SPATIAL INDEX specific functions.
ibuf_upgrade_needed(): Check if the change buffer needs to be updated.
ibuf_upgrade(): Merge and upgrade the change buffer after all redo log
has been applied. Free any pages consumed by the change buffer, and
zero out the change buffer root page to mark the upgrade completed,
and to prevent a downgrade to an earlier version.
dict_load_tablespaces(): Renamed from
dict_check_tablespaces_and_store_max_id(). This needs to be invoked
before ibuf_upgrade().
btr_cur_open_at_rnd_pos(): Specialize for use in persistent statistics.
The change buffer merge does not need this function anymore.
btr_page_alloc(): Renamed from btr_page_alloc_low(). We no longer
allocate any change buffer pages.
btr_cur_open_at_rnd_pos(): Specialize for use in persistent statistics.
The change buffer merge does not need this function anymore.
row_search_index_entry(), btr_lift_page_up(): Add a parameter thr
for the SPATIAL INDEX case.
rtr_page_split_and_insert(): Specialized from btr_page_split_and_insert().
rtr_root_raise_and_insert(): Specialized from btr_root_raise_and_insert().
Note: The support for upgrading from the MySQL 3.23 or MySQL 4.0
change buffer format that predates the MySQL 4.1 introduction of
the option innodb_file_per_table was removed in MySQL 5.6.5
as part of mysql/mysql-server@69b6241a79
and MariaDB 10.0.11 as part of 1d0f70c2f8.
In the tests innodb.log_upgrade and innodb.log_corruption, we create
valid (upgraded) change buffer pages.
Tested by: Matthias Leich
We introduce the following settable Boolean global variables:
innodb_log_file_write_through: Whether writes to ib_logfile0 are
write-through (disabling any caching, as in O_SYNC or O_DSYNC).
innodb_data_file_write_through: Whether writes to any InnoDB data files
(including the temporary tablespace) are write-through.
innodb_data_file_buffering: Whether the file system cache is enabled
for InnoDB data files.
All these parameters are OFF by default, that is, the file system cache
will be disabled, but any hardware caching is enabled, that is,
explicit calls to fsync(), fdatasync() or similar functions are needed.
On systems that support FUA it may make sense to enable write-through,
to avoid extra system calls.
If the deprecated read-only start-up parameter is set to one of the
following values, then the values of the 4 Boolean flags (the above 3
plus innodb_log_file_buffering) will be set as follows:
O_DSYNC:
innodb_log_file_write_through=ON, innodb_data_file_write_through=ON,
innodb_data_file_buffering=OFF, and
(if supported) innodb_log_file_buffering=OFF.
fsync, littlesync, nosync, or (Microsoft Windows specific) normal:
innodb_log_file_write_through=OFF, innodb_data_file_write_through=OFF,
and innodb_data_file_buffering=ON.
Note: fsync() or fdatasync() will only be disabled if the separate
parameter debug_no_sync (in the code, my_disable_sync) is set.
In mariadb-backup, the parameter innodb_flush_method will be ignored.
The Boolean parameters can be modified by SET GLOBAL while the
server is running. This will require reopening the ib_logfile0
or all currently open InnoDB data files.
We will open files straight in O_DSYNC or O_SYNC mode when applicable.
Data files we will try to open straight in O_DIRECT mode when the
page size is at least 4096 bytes. For atomically creating data files,
we will invoke os_file_set_nocache() to enable O_DIRECT afterwards,
because O_DIRECT is not supported on some file systems. We will also
continue to invoke os_file_set_nocache() on ib_logfile0 when
innodb_log_file_buffering=OFF can be fulfilled.
For reopening the ib_logfile0, we use the same logic that was developed
for online log resizing and reused for updates of
innodb_log_file_buffering.
Reopening all data files is implemented in the new function
fil_space_t::reopen_all().
Reviewed by: Vladislav Vaintroub
Tested by: Matthias Leich
The MDEV-25004 test innodb_fts.versioning is omitted because ever since
commit 685d958e38 InnoDB would not allow
writes to a database where the redo log file ib_logfile0 is missing.
to copy datafile
- Mariabackup fails to copy the undo log tablespace when it undergoes
truncation. So Mariabackup should detect the redo log which does
undo tablespace truncation and also backup should read the minimum
file size of the tablespace and ignore the error while reading.
- Throw error when innodb undo tablespace read failed, but backup
doesn't find the redo log for undo tablespace truncation
io_watching_thread(): Declare as a detachable thread, similar to
log_copying_thread().
stop_backup_threads(): Wait for both log_copying_thread and
io_watching_thread to clear their flags. Expect log_sys.mutex
to be held by the caller.
xtrabackup_backup_func(): Initialize log_copying_stop before
creating io_watching_thread. This prevents a race condition
where io_watching_thread() could wait on the condition variable
before it had been fully initialized. This race condition would
cause a hang in the GNU libc implementation of pthread_cond_destroy()
at the end of stop_backup_threads().
This race condition was introduced in
commit 38fd7b7d91 (MDEV-21452).
The variable was not really being used for anything. The parameters
innodb_read_io_threads, innodb_write_io_threads have replaced
innodb_file_io_threads.
- Mariabackup fails to open the undo tablespaces while applying delta
files to the corresponding data file. Mariabackup opens the
undo tablespaces first time in srv_undo_tablespaces_init() and does
tries to open the undo tablespaces in xtrabackup_apply_deltas() with
conflicting mode and leads to the failure.
- Mariabackup should close the undo tablespaces before applying
the incremental delta files.
os_file_read(): Merged with os_file_read_no_error_handling().
Crashing on a partial page read is as unhelpful as crashing on a
corrupted page read (commit 0b47c126e3).
Report the file name if it is available via IORequest.
