This patch is the result of running
run-clang-tidy -fix -header-filter=.* -checks='-*,modernize-use-equals-default' .
Code style changes have been done on top. The result of this change
leads to the following improvements:
1. Binary size reduction.
* For a -DBUILD_CONFIG=mysql_release build, the binary size is reduced by
~400kb.
* A raw -DCMAKE_BUILD_TYPE=Release reduces the binary size by ~1.4kb.
2. Compiler can better understand the intent of the code, thus it leads
to more optimization possibilities. Additionally it enabled detecting
unused variables that had an empty default constructor but not marked
so explicitly.
Particular change required following this patch in sql/opt_range.cc
result_keys, an unused template class Bitmap now correctly issues
unused variable warnings.
Setting Bitmap template class constructor to default allows the compiler
to identify that there are no side-effects when instantiating the class.
Previously the compiler could not issue the warning as it assumed Bitmap
class (being a template) would not be performing a NO-OP for its default
constructor. This prevented the "unused variable warning".
row_purge_get_partial(): Replaces trx_undo_rec_get_partial_row().
Also copy the purge_node_t::ref to the purge_node_t::row.
In this way, the clustered index key fields will always be
available, even if thanks to
commit d384ead0f0 (MDEV-14799)
they would no longer be repeated in the remaining part of the
undo log record.
trx->mysql_thd can be zeroed-out between thd_get_thread_id() and
thd_query_safe() calls in fill_trx_row(). trx_disconnect_prepared() zeroes out
trx->mysql_thd. And this can cause null pointer dereferencing in
fill_trx_row().
fill_trx_row() is invoked from fetch_data_into_cache() under trx_sys.mutex.
Bug fix is in reseting trx_t::mysql_thd in trx_disconnect_prepared() under
trx_sys.mutex lock too.
MTR test case can't be created for the fix, as we need to wait for
trx_t::mysql_thd reseting in fill_trx_row() after trx_t::mysql_thd was
checked for null while trx_sys.mutex is held. But trx_t::mysql_thd must be
reset in trx_disconnect_prepared() under trx_sys.mutex. There will be deadlock.
trx_undo_page_report_rename(): Use the correct maximum length of
a table name. Both the database name and the table name can be up to
NAME_CHAR_LEN (64 characters) times 5 bytes per character in the
my_charset_filename encoding. They are not encoded in UTF-8!
fil_op_write_log(): Reserve the correct amount of log buffer for
a rename operation. The file name will be appended by
mlog_catenate_string().
rename_file_ext(): Reserve a large enough buffer for the file names.
In commit c7d0448797 (MDEV-15132)
MariaDB Server 10.3 stopped writing the latest transaction identifier
to the TRX_SYS page. Instead, the transaction identifier will be
recovered from undo log pages.
Unfortunately, before commit 3926673ce7
and mysql/mysql-server@dc29792ff2
(MySQL 5.1.48 or MariaDB 5.1.48) InnoDB did not always initialize all
data fields, but some garbage could be left behind in unused parts
of data pages.
In undo log pages that are essentially free, but added to a list for
reuse (TRX_UNDO_CACHED) the TRX_UNDO_TRX_NO fields could contain garbage,
instead of 0. As long as such undo pages are being reused and never
marked completely free, the garbage contents may remain forever.
In fact, the function trx_undo_header_create() and the record
MLOG_UNDO_HDR_CREATE will only initialize TRX_UNDO_TRX_ID, but leave
TRX_UNDO_TRX_NO uninitialized.
trx_undo_mem_create_at_db_start(): Only read the TRX_UNDO_TRX_NO
fields of TRX_UNDO_CACHED pages if the TRX_UNDO_PAGE_TYPE is 0,
that is, the page was updated by MariaDB Server 10.3. Earlier versions
would always write the TRX_UNDO_PAGE_TYPE as 1 or 2.
trx_undo_header_create(): Zero out the TRX_UNDO_TRX_NO field.
Strictly speaking, this will change the semantics of the
MLOG_UNDO_HDR_CREATE record, but it should not do any harm to
overwrite a potentially garbage field with zeroes.
Note: This fix will only help future upgrades straight from
MariaDB Server 10.2 or MySQL 5.6 or earlier. If such an upgrade has
already been made, then an earlier server startup could have
fast-forwarded the transaction ID sequence to a large value.
If this large value cannot be represented in 48 bits (the size of
the DB_TRX_ID column in clustered index records), then various
strange things can happen.
Since commit fb335b48b5 we may have
a null pointer in purge_sys.query when fetch_data_into_cache() is
invoked and innodb_force_recovery>4. This is because the call to
purge_sys.create() would be skipped.
fetch_data_into_cache(): Load the purge_sys pseudo transaction pointer
to a local variable (null pointer if purge_sys is not initialized).
trx_commit_in_memory(): Do not release the rseg reference before
trx_undo_commit_cleanup() has been invoked and the current transaction
is truly done with the rollback segment. The purpose of the reference
count is to prevent data races with trx_purge_truncate_history().
This is based on
mysql/mysql-server@ac79aa1522.
trx_rseg_header_create(): Add a parameter for the value that is
to be written to TRX_RSEG_MAX_TRX_ID. If we omit this write, then
the updated test innodb.undo_truncate will fail for the 4k, 8k, 16k
page sizes. This was broken ever since
commit 947efe17ed (MDEV-15158)
removed the writes of transaction identifiers to the TRX_SYS page.
srv_do_purge(): Truncate undo tablespaces also during slow shutdown
(innodb_fast_shutdown=0).
Thanks to Krunal Bauskar for noticing this problem.
At least since commit 055a3334ad
(MDEV-13564) the undo log truncation in InnoDB did not work correctly.
The main issue is that during the execution of
trx_purge_truncate_history() some pages of the newly truncated
undo tablespace could be discarded.
fsp_try_extend_data_file(): Apply the peculiar rounding of
fil_space_t::size_in_header only to the system tablespace,
whose size can be expressed in megabytes in a configuration parameter.
Other files may freely grow by a number of pages.
fseg_alloc_free_page_low(): Do allow the extension of undo tablespaces,
and mention the file name in the error message.
mtr_t::commit_shrink(): Implement crash-safe shrinking of a tablespace
file. First, durably write the log, then shrink the file, and finally
release the page latches of the rebuilt tablespace. Refactored from
trx_purge_truncate_history().
log_write_and_flush_prepare(), log_write_and_flush(): New functions
to durably write log during mtr_t::commit_shrink().
trx_purge_rseg_get_next_history_log(): Fix a race condition that
was introduced in commit e46f76c974
(MDEV-15912). The buffer pool page contents must not be accessed
while not holding a page latch. The page latch was released by
mtr_t::commit().
This race resulted in an ASAN heap-use-after-poison during a stress test.
trx_t::will_lock: Changed the type to bool.
trx_t::is_autocommit_non_locking(): Replaces
trx_is_autocommit_non_locking().
trx_is_ac_nl_ro(): Remove (replaced with equivalent assertion expressions).
assert_trx_nonlocking_or_in_list(): Remove.
Replaced with at least as strict checks in each place.
check_trx_state(): Moved to a static function; partially replaced with
individual debug assertions implementing equivalent or stricter checks.
This is a backport of commit 7b51d11cca
from 10.5.
In commit 2e814d4702 on MariaDB 10.2
the switch case statement in trx_flush_log_if_needed_low() regressed.
Since 10.2 this code was refactored to have switches in descending
order, so value of 3 for innodb_flush_log_at_trx_commit is behaving
the same as value of 2, that is no FSYNC is being enforced during
COMMIT phase. The switch should however not be empty and cases 2 and 3
should not have the identical contents.
As per documentation, setting innodb_flush_log_at_trx_commit to 3
should do FSYNC to disk if innodb_flush_log_at_trx_commit is set to 3.
This fixes the regression so that the switch statement again does
what users expect the setting should do.
All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.
trx_undo_mem_create_at_db_start(): Relax too strict upgrade checks
that were introduced in
commit e46f76c974 (MDEV-15912).
On commit, pages will typically be set to TRX_UNDO_CACHED state.
Having the type TRX_UNDO_INSERT in such pages is common and
unproblematic; the type would be reset in trx_undo_reuse_cached().
trx_rseg_array_init(): On failure, clean up the rollback segments
that were initialized so far, to avoid an assertion failure later
during shutdown.
trx_undo_report_row_operation(): Fix a race condition that was introduced
in commit f74023b955 (MDEV-15090).
We must not access undo_block after the page latch has been released
in mtr_t::commit(), because the block could be evicted or replaced.
Let us simply refuse an upgrade from earlier versions if the
upgrade procedure was not followed. This simplifies the purge,
commit, and rollback of transactions.
Before upgrading to MariaDB 10.3 or later, a clean shutdown
of the server (with innodb_fast_shutdown=1 or 0) is necessary,
to ensure that any incomplete transactions are rolled back.
The undo log format was changed in MDEV-12288. There is only
one persistent undo log for each transaction.
InnoDB startup hangs if a DDL transaction needs to be
rolled back and a recovered transaction on statistics
tables exists. In that case, InnoDB should rollback
the transaction which holds locks on innodb_table_stats
or innodb_index_stats during trx_rollback_or_clean_recovered().
Between btr_pcur_store_position() and btr_pcur_restore_position()
it is possible that purge empties a table and enlarges
index->n_core_fields and index->n_core_null_bytes.
Therefore, we must cache index->n_core_fields in
btr_pcur_t::old_n_core_fields so that btr_pcur_t::old_rec can be
parsed correctly.
Unfortunately, this is a huge change, because we will replace
"bool leaf" parameters with "ulint n_core"
(passing index->n_core_fields, or 0 for non-leaf pages).
For special cases where we know that index->is_instant() cannot hold,
we may also pass index->n_fields.
trx_sys_any_active_transactions(): Remove a bogus debug assertion.
In trx_commit_in_memory() and trx_erase_lists(), we will remove
the transaction from trx_sys->rw_trx_list and set the state to
TRX_STATE_COMMITTED_IN_MEMORY.
Before MDEV-14638, there was no race condition between the
execution of fetch_data_into_cache() and transaction commit.
fetch_data_into_cache(): Acquire trx_t::mutex before checking
trx_t::state, to prevent a concurrent transition from
TRX_STATE_COMMITTED_IN_MEMORY to TRX_STATE_NOT_STARTED
in trx_commit_in_memory().
This is a backport of commit 18535a4028
from 10.6.
lock_release(): Implement innodb_evict_tables_on_commit_debug.
Before releasing any locks, collect the identifiers of tables to
be evicted. After releasing all locks, look up for the tables and
evict them if it is safe to do so.
trx_commit_in_memory(): Invoke trx_update_mod_tables_timestamp()
before lock_release(), so that our locks will protect the tables
from being evicted.
Ever since commit 947efe17ed
InnoDB no longer writes binlog position in one place.
It will not at all be written to the TRX_SYS page, and
instead it will be written to the undo log header page that
changes the transaction state.
trx_rseg_mem_restore(): Recover the information from the latest
written page.
Some DML operations on tables having unique secondary keys cause scanning
in the secondary index, for instance to find potential unique key violations
in the seconday index. This scanning may involve GAP locking in the index.
As this locking happens also when applying replication events in high priority
applier threads, there is a probabality for lock conflicts between two wsrep
high priority threads.
This PR avoids lock conflicts of high priority wsrep threads, which do
secondary index scanning e.g. for duplicate key detection.
The actual fix is the patch in sql_class.cc:thd_need_ordering_with(), where
we allow relaxed GAP locking protocol between wsrep high priority threads.
wsrep high priority threads (replication appliers, replayers and TOI processors)
are ordered by the replication provider, and they will not need serializability
support gained by secondary index GAP locks.
PR contains also a mtr test, which exercises a scenario where two replication
applier threads have a false positive conflict in GAP of unique secondary index.
The conflicting local committing transaction has to replay, and the test verifies
also that the replaying phase will not conflict with the latter repllication applier.
Commit also contains new test scenario for galera.galera_UK_conflict.test,
where replayer starts applying after a slave applier thread, with later seqno,
has advanced to commit phase. The applier and replayer have false positive GAP
lock conflict on secondary unique index, and replayer should ignore this.
This test scenario caused crash with earlier version in this PR, and to fix this,
the secondary index uniquenes checking has been relaxed even further.
Now innodb trx_t structure has new member: bool wsrep_UK_scan, which is set to
true, when high priority thread is performing unique secondary index scanning.
The member trx_t::wsrep_UK_scan is defined inside WITH_WSREP directive, to make
it possible to prepare a MariaDB build where this additional trx_t member is
not present and is not used in the code base. trx->wsrep_UK_scan is set to true
only for the duration of function call for: lock_rec_lock() trx->wsrep_UK_scan
is used only in lock_rec_has_to_wait() function to relax the need to wait if
wsrep_UK_scan is set and conflicting transaction is also high priority.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>
A race condition may occur between the execution of transaction commit,
and an execution of a KILL statement that would attempt to abort that
transaction.
MDEV-17092 worked around this race condition by modifying InnoDB code.
After that issue was closed, Sergey Vojtovich pointed out that this
race condition would better be fixed above the storage engine layer:
If you look carefully into the above, you can conclude that
thd->free_connection() can be called concurrently with
KILL/thd->awake(). Which is the bug. And it is partially fixed in
THD::~THD(), that is destructor waits for KILL completion:
Fix: Add necessary mutex operations to THD::free_connection()
and move WSREP specific code also there. This ensures that no
one is using THD while we do free_connection(). These mutexes
will also ensures that there can't be concurrent KILL/THD::awake().
innobase_kill_query
We can now remove usage of trx_sys_mutex introduced on MDEV-17092.
trx_t::free()
Poison trx->state and trx->mysql_thd
This patch is validated with an RQG run similar to the one that
reproduced MDEV-17092.
