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".
GCC 12 complains if a reference to an uninitialized object is
being passed to a constructor. The mysql_mutex_t, mysql_cond_t
would be initialized in the constructor body, which is executed
after the initializer list. There is no problem passing a pointer
instead of a reference. The wrapper classes do not dereference
the pointers in the constructor or destructor, so there does not
appear to be any correctness issue.
* MDEV-16509 Improve wsrep commit performance with binlog disabled
Release commit order critical section early after trx_commit_low() if
binlog is not transaction coordinator. In order to avoid two phase commit,
binlog_hton is not registered for THD during IO_CACHE population.
Implemented a test which verifies that the transactions release
commit order early.
This optimization will change behavior during recovery as the commit
is not two phase when binlog is off. Fixed and recorded wsrep-recover-v25
and wsrep-recover to match the behavior.
* MDEV-18730 Ordering for wsrep binlog group commit
Previously out of order execution was allowed for wsrep commits.
Established proper ordering by populating wait_for_commit
for every wsrep THD and making group commit leader to wait for
prior commits before proceeding to trx_group_commit_leader().
* MDEV-18730 Added a test case to verify correct commit ordering
* MDEV-16509, MDEV-18730 Review fixes
Use WSREP_EMULATE_BINLOG() macro to decide if the binlog_hton
should be registered. Whitespace/syntax fixes and cleanups.
* MDEV-16509 Require binlog for galera_var_innodb_disallow_writes test
If the commit to InnoDB is done in one phase, the native InnoDB behavior
is that the transaction is committed in memory before it is persisted to
disk. This means that the innodb_disallow_writes=ON may not prevent
transaction to become visible to other readers before commit is completely
over. On the other hand, if the commit is two phase (as it is with binlog),
the transaction will be blocked in prepare phase.
Fixed the test to use binlog, which enforces two phase commit, which
in turn makes commit to block before the changes become visible to
other connections. This guarantees that the test produces expected
result.
