For more convenient monitoring of something that could greatly affect
the volume of page writes, we add the status variable
Innodb_buffer_pool_pages_split that was previously only available
via information_schema.innodb_metrics as "innodb_page_splits".
This was suggested by Axel Schwenke.
buf_flush_page_count: Replaced with buf_pool.stat.n_pages_written.
We protect buf_pool.stat (except n_page_gets) with buf_pool.mutex
and remove unnecessary export_vars indirection.
buf_pool.flush_list_bytes: Moved from buf_pool.stat.flush_list_bytes.
Protected by buf_pool.flush_list_mutex.
buf_pool_t::page_cleaner_status: Replaces buf_pool_t::n_flush_LRU_,
buf_pool_t::n_flush_list_, and buf_pool_t::page_cleaner_is_idle.
Protected by buf_pool.flush_list_mutex. We will exclusively broadcast
buf_pool.done_flush_list by the buf_flush_page_cleaner thread,
and only wait for it when communicating with buf_flush_page_cleaner.
There is no need to keep a count of pending writes by the
buf_pool.flush_list processing. A single flag suffices for that.
Waits for page write completion can be performed by
simply waiting on block->page.lock, or by invoking
buf_dblwr.wait_for_page_writes().
buf_LRU_block_free_non_file_page(): Broadcast buf_pool.done_free and
set buf_pool.try_LRU_scan when freeing a page. This would be
executed also as part of buf_page_write_complete().
buf_page_write_complete(): Do not broadcast buf_pool.done_flush_list,
and do not acquire buf_pool.mutex unless buf_pool.LRU eviction is needed.
Let buf_dblwr count all writes to persistent pages and broadcast a
condition variable when no outstanding writes remain.
buf_flush_page_cleaner(): Prioritize LRU flushing and eviction right after
"furious flushing" (lsn_limit). Simplify the conditions and reduce the
hold time of buf_pool.flush_list_mutex. Refuse to shut down
or sleep if buf_pool.ran_out(), that is, LRU eviction is needed.
buf_pool_t::page_cleaner_wakeup(): Add the optional parameter for_LRU.
buf_LRU_get_free_block(): Protect buf_lru_free_blocks_error_printed
with buf_pool.mutex. Invoke buf_pool.page_cleaner_wakeup(true) to
to ensure that buf_flush_page_cleaner() will process the LRU flush
request.
buf_do_LRU_batch(), buf_flush_list(), buf_flush_list_space():
Update buf_pool.stat.n_pages_written when submitting writes
(while holding buf_pool.mutex), not when completing them.
buf_page_t::flush(), buf_flush_discard_page(): Require that
the page U-latch be acquired upfront, and remove
buf_page_t::ready_for_flush().
buf_pool_t::delete_from_flush_list(): Remove the parameter "bool clear".
buf_flush_page(): Count pending page writes via buf_dblwr.
buf_flush_try_neighbors(): Take the block of page_id as a parameter.
If the tablespace is dropped before our page has been written out,
release the page U-latch.
buf_pool_invalidate(): Let the caller ensure that there are no
outstanding writes.
buf_flush_wait_batch_end(false),
buf_flush_wait_batch_end_acquiring_mutex(false):
Replaced with buf_dblwr.wait_for_page_writes().
buf_flush_wait_LRU_batch_end(): Replaces buf_flush_wait_batch_end(true).
buf_flush_list(): Remove some broadcast of buf_pool.done_flush_list.
buf_flush_buffer_pool(): Invoke also buf_dblwr.wait_for_page_writes().
buf_pool_t::io_pending(), buf_pool_t::n_flush_list(): Remove.
Outstanding writes are reflected by buf_dblwr.pending_writes().
buf_dblwr_t::init(): New function, to initialize the mutex and
the condition variables, but not the backing store.
buf_dblwr_t::is_created(): Replaces buf_dblwr_t::is_initialised().
buf_dblwr_t::pending_writes(), buf_dblwr_t::writes_pending:
Keeps track of writes of persistent data pages.
buf_flush_LRU(): Allow calls while LRU flushing may be in progress
in another thread.
Tested by Matthias Leich (correctness) and Axel Schwenke (performance)
Adaptive flushing is enabled by setting innodb_max_dirty_pages_pct_lwm>0
(not default) and innodb_adaptive_flushing=ON (default).
There is also the parameter innodb_adaptive_flushing_lwm
(default: 10 per cent of the log capacity). It should enable some
adaptive flushing even when innodb_max_dirty_pages_pct_lwm=0.
That is not being changed here.
This idea was first presented by Inaam Rana several years ago,
and I discussed it with Jean-François Gagné at FOSDEM 2023.
buf_flush_page_cleaner(): When we are not near the log capacity limit
(neither buf_flush_async_lsn nor buf_flush_sync_lsn are set),
also try to move clean blocks from the buf_pool.LRU list to buf_pool.free
or initiate writes (but not the eviction) of dirty blocks, until
the remaining I/O capacity has been consumed.
buf_flush_LRU_list_batch(): Add the parameter bool evict, to specify
whether dirty least recently used pages (from buf_pool.LRU) should
be evicted immediately after they have been written out. Callers outside
buf_flush_page_cleaner() will pass evict=true, to retain the existing
behaviour.
buf_do_LRU_batch(): Add the parameter bool evict.
Return counts of evicted and flushed pages.
buf_flush_LRU(): Add the parameter bool evict.
Assume that the caller holds buf_pool.mutex and
will invoke buf_dblwr.flush_buffered_writes() afterwards.
buf_flush_list_holding_mutex(): A low-level variant of buf_flush_list()
whose caller must hold buf_pool.mutex and invoke
buf_dblwr.flush_buffered_writes() afterwards.
buf_flush_wait_batch_end_acquiring_mutex(): Remove. It is enough to have
buf_flush_wait_batch_end().
page_cleaner_flush_pages_recommendation(): Avoid some floating-point
arithmetics.
buf_flush_page(), buf_flush_check_neighbor(), buf_flush_check_neighbors(),
buf_flush_try_neighbors(): Rename the parameter "bool lru" to "bool evict".
buf_free_from_unzip_LRU_list_batch(): Remove the parameter.
Only actual page writes will contribute towards the limit.
buf_LRU_free_page(): Evict freed pages of temporary tables.
buf_pool.done_free: Broadcast whenever a block is freed
(and buf_pool.try_LRU_scan is set).
buf_pool_t::io_buf_t::reserve(): Retry indefinitely.
During the test encryption.innochecksum we easily run out of
these buffers for PAGE_COMPRESSED or ENCRYPTED pages.
Tested by Matthias Leich and Axel Schwenke
lock_sec_rec_some_has_impl(): Remove a harmful condition that caused the
performance regression and should not have been added in
commit b6e41e3872 in the first place.
Locking transactions that have not modified any persistent tables
can carry the transaction identifier 0.
trx_t::max_inactive_id: A cache for trx_sys_t::find_same_or_older().
The value is not reset on transaction commit so that previous results
can be reused for subsequent transactions. The smallest active
transaction ID can only increase over time, not decrease.
trx_sys_t::find_same_or_older(): Remember the maximum previous id for which
rw_trx_hash.iterate() returned false, to avoid redundant iterations.
lock_sec_rec_read_check_and_lock(): Add an early return in case we are
already holding a covering table lock.
lock_rec_convert_impl_to_expl(): Add a template parameter to avoid
a redundant run-time check on whether the index is secondary.
lock_rec_convert_impl_to_expl_for_trx(): Move some code from
lock_rec_convert_impl_to_expl(), to reduce code duplication due
to the added template parameter.
Reviewed by: Vladislav Lesin
Tested by: Matthias Leich
This is a follow-up to
commit de4030e4d4 (MDEV-30400),
which fixed some hangs related to B-tree split or merge.
btr_root_block_get(): Use and update the root page guess. This is just
a minor performance optimization, not affecting correctness.
btr_validate_level(): Remove the parameter "lockout", and always
acquire an exclusive dict_index_t::lock in CHECK TABLE without QUICK.
This is needed in order to avoid latching order violation in
btr_page_get_father_node_ptr_for_validate().
btr_cur_need_opposite_intention(): Return true in case
btr_cur_compress_recommendation() would hold later during the
mini-transaction, or if a page underflow or overflow is possible.
If we return true, our caller will escalate to aqcuiring an exclusive
dict_index_t::lock, to prevent a latching order violation and deadlock
during btr_compress() or btr_page_split_and_insert().
btr_cur_t::search_leaf(), btr_cur_t::open_leaf():
Also invoke btr_cur_need_opposite_intention() on the leaf page.
btr_cur_t::open_leaf(): When escalating to exclusive index locking,
acquire exclusive latches on all pages as well.
innobase_instant_try(): Return an error code if the root page cannot
be retrieved.
In addition to the normal stress testing with Random Query Generator (RQG)
this has been tested with
./mtr --mysqld=--loose-innodb-limit-optimistic-insert-debug=2
but with the injection in btr_cur_optimistic_insert() for non-leaf pages
adjusted so that it would use the value 3. (Otherwise, infinite page
splits could occur in some mtr tests.)
Tested by: Matthias Leich
fil_node_open_file_low() tries to close files from the top of
fil_system.space_list if the number of opened files is exceeded.
It invokes fil_space_t::try_to_close(), which iterates the list searching
for the first opened space. Then it just closes the space, leaving it in
the same position in fil_system.space_list.
On heavy files opening, like during 'SHOW TABLE STATUS ...' execution,
if the number of opened files limit is reached,
fil_space_t::try_to_close() iterates more and more closed spaces before
reaching any opened space for each fil_node_open_file_low() call. What
causes performance regression if the number of spaces is big enough.
The fix is to keep opened spaces at the top of fil_system.space_list,
and move closed files at the end of the list.
For this purpose fil_space_t::space_list_last_opened pointer is
introduced. It points to the last inserted opened space in
fil_space_t::space_list. When space is opened, it's inserted to the
position just after the pointer points to in fil_space_t::space_list to
preserve the logic, inroduced in MDEV-23855. Any closed space is added
to the end of fil_space_t::space_list.
As opened spaces are located at the top of fil_space_t::space_list,
fil_space_t::try_to_close() finds opened space faster.
There can be the case when opened and closed spaces are mixed in
fil_space_t::space_list if fil_system.freeze_space_list was set during
fil_node_open_file_low() execution. But this should not cause any error,
as fil_space_t::try_to_close() still iterates spaces in the list.
There is no need in any test case for the fix, as it does not change any
functionality, but just fixes performance regression.
- InnoDB fails to reset the check_foreigns and check_unique_secondary
in trx_t::free(), trx_t::commit_cleanup(). This lead to bulk insert
in internal innodb fts table operation.
Starting with commit 0de3be8cfd (MDEV-30671),
the field TRX_UNDO_NEEDS_PURGE lost its previous meaning.
The following scenario is possible:
(1) InnoDB is killed at a point of time corresponding to the durable
execution of some fseg_free_step_not_header() but not
trx_purge_remove_log_hdr().
(2) After restart, the affected pages are allocated for something else.
(3) Purge will attempt to access the newly reallocated pages when looking
for some old undo log records.
trx_purge_free_segment(): Invoke trx_purge_remove_log_hdr() as the first
thing, to be safe. If the server is killed, some pages will never be
freed. That is the lesser evil. Also, before each mtr.start(), invoke
log_free_check() to prevent ib_logfile0 overrun.
It is not safe to invoke trx_purge_free_segment() or execute
innodb_undo_log_truncate=ON before all undo log records in
the rollback segment has been processed.
A prominent failure that would occur due to premature freeing of
undo log pages is that trx_undo_get_undo_rec() would crash when
trying to copy an undo log record to fetch the previous version
of a record.
If trx_undo_get_undo_rec() was not invoked in the unlucky time frame,
then the symptom would be that some committed transaction history is
never removed. This would be detected by CHECK TABLE...EXTENDED that
was impleented in commit ab0190101b.
Such a garbage collection leak should be possible even when using
innodb_undo_log_truncate=OFF, just involving trx_purge_free_segment().
trx_rseg_t::needs_purge: Change the type from Boolean to a transaction
identifier, noting the most recent non-purged transaction, or 0 if
everything has been purged. On transaction start, we initialize this
to 1 more than the transaction start ID. On recovery, the field may be
adjusted to the transaction end ID (TRX_UNDO_TRX_NO) if it is larger.
The field TRX_UNDO_NEEDS_PURGE becomes write-only; only some debug
assertions that would validate the value. The field reflects the old
inaccurate Boolean field trx_rseg_t::needs_purge.
trx_undo_mem_create_at_db_start(), trx_undo_lists_init(),
trx_rseg_mem_restore(): Remove the parameter max_trx_id.
Instead, store the maximum in trx_rseg_t::needs_purge,
where trx_rseg_array_init() will find it.
trx_purge_free_segment(): Contiguously hold a lock on
trx_rseg_t to prevent any concurrent allocation of undo log.
trx_purge_truncate_rseg_history(): Only invoke trx_purge_free_segment()
if the rollback segment is empty and there are no pending transactions
associated with it.
trx_purge_truncate_history(): Only proceed with innodb_undo_log_truncate=ON
if trx_rseg_t::needs_purge indicates that all history has been purged.
Tested by: Matthias Leich
The initial issue was in assertion failure, which checked the equality
of lock to cancel with trx->lock.wait_lock in lock_sys_t::cancel().
If we analyze lock_sys_t::cancel() code from the perspective of
trx->lock.wait_lock racing, we won't find the error there, except the
cases when we need to reload it after the corresponding latches
acquiring.
So the fix is just to remove the assertion and reload
trx->lock.wait_lock after acquiring necessary latches.
Reviewed by: Marko Mäkelä <marko.makela@mariadb.com>
This is a partial revert of
commit 8b6a308e46 (MDEV-29883)
and a follow-up to the
merge commit 394fc71f4f (MDEV-24569).
The latching order related to any operation that accesses the allocation
metadata of an InnoDB index tree is as follows:
1. Acquire dict_index_t::lock in non-shared mode.
2. Acquire the index root page latch in non-shared mode.
3. Possibly acquire further index page latches. Unless an exclusive
dict_index_t::lock is held, this must follow the root-to-leaf,
left-to-right order.
4. Acquire a *non-shared* fil_space_t::latch.
5. Acquire latches on the allocation metadata pages.
6. Possibly allocate and write some pages, or free some pages.
btr_get_size_and_reserved(), dict_stats_update_transient_for_index(),
dict_stats_analyze_index(): Acquire an exclusive fil_space_t::latch
in order to avoid a deadlock in fseg_n_reserved_pages() in case of
concurrent access to multiple indexes sharing the same "inode page".
fseg_page_is_allocated(): Acquire an exclusive fil_space_t::latch
in order to avoid deadlocks. All callers are holding latches
on a buffer pool page, or an index, or both.
Before commit edbde4a11f (MDEV-24167)
a third mode was available that would not conflict with the shared
fil_space_t::latch acquired by ha_innobase::info_low(),
i_s_sys_tablespaces_fill_table(),
or i_s_tablespaces_encryption_fill_table().
Because those calls should be rather rare, it makes sense to use
the simple rw_lock with only shared and exclusive modes.
fil_crypt_get_page_throttle(): Avoid invoking fseg_page_is_allocated()
on an allocation bitmap page (which can never be freed), to avoid
acquiring a shared latch on top of an exclusive one.
mtr_t::s_lock_space(), MTR_MEMO_SPACE_S_LOCK: Remove.
buf_pool_t::watch_set(): Always buffer-fix a block if one was found,
no matter if it is a watch sentinel or a buffer page. The type of
the block descriptor will be rechecked in buf_page_t::watch_unset().
Do not expect the caller to acquire the page hash latch. Starting with
commit bd5a6403ca it is safe to release
buf_pool.mutex before acquiring a buf_pool.page_hash latch.
buf_page_get_low(): Adjust to the changed buf_pool_t::watch_set().
This simplifies the logic and fixes a bug that was reproduced when
using debug builds and the setting innodb_change_buffering_debug=1.
buf_read_page_low(): Map the buf_page_t::read_complete() return
value DB_FAIL to DB_PAGE_CORRUPTED. The purpose of the DB_FAIL
return value is to avoid error log noise when read-ahead brings
in an unused page that is typically filled with NUL bytes.
If a synchronous read is bringing in a corrupted page where the
page frame does not contain the expected tablespace identifier and
page number, that must be treated as an attempt to read a corrupted
page. The correct error code for this is DB_PAGE_CORRUPTED.
The error code DB_FAIL is not handled by row_mysql_handle_errors().
This was missed in commit 0b47c126e3
(MDEV-13542).
This almost completely reverts
commit acd23da4c2 and
retains a safe optimization:
recv_sys_t::parse(): Remove any old redo log records for the
truncated tablespace, to free up memory earlier.
If recovery consists of multiple batches, then recv_sys_t::apply()
will must invoke recv_sys_t::trim() again to avoid wrongly
applying old log records to an already truncated undo tablespace.
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".
recv_sys_t::parse(): Discard old page-level redo log when parsing
a TRIM_PAGES record.
recv_sys_t::apply(): trim() was invoked in parse() already.
recv_sys_t::truncated_undo_spaces[]: Only store the size, no LSN.
This also fixes part of MDEV-29835 Partial server freeze
which is caused by violations of the latching order that was
defined in https://dev.mysql.com/worklog/task/?id=6326
(WL#6326: InnoDB: fix index->lock contention). Unless the
current thread is holding an exclusive dict_index_t::lock,
it must acquire page latches in a strict parent-to-child,
left-to-right order. Not all cases of MDEV-29835 are fixed yet.
Failure to follow the correct latching order will cause deadlocks
of threads due to lock order inversion.
As part of these changes, the BTR_MODIFY_TREE mode is modified
so that an Update latch (U a.k.a. SX) will be acquired on the
root page, and eXclusive latches (X) will be acquired on all pages
leading to the leaf page, as well as any left and right siblings
of the pages along the path. The DEBUG_SYNC test innodb.innodb_wl6326
will be removed, because at the time the DEBUG_SYNC point is hit,
the thread is actually holding several page latches that will be
blocking a concurrent SELECT statement.
We also remove double bookkeeping that was caused due to excessive
information hiding in mtr_t::m_memo. We simply let mtr_t::m_memo
store information of latched pages, and ensure that
mtr_memo_slot_t::object is never a null pointer.
The tree_blocks[] and tree_savepoints[] were redundant.
buf_page_get_low(): If innodb_change_buffering_debug=1, to avoid
a hang, do not try to evict blocks if we are holding a latch on
a modified page. The test innodb.innodb-change-buffer-recovery
will be removed, because change buffering may no longer be forced
by debug injection when the change buffer comprises multiple pages.
Remove a debug assertion that could fail when
innodb_change_buffering_debug=1 fails to evict a page.
For other cases, the assertion is redundant, because we already
checked that right after the got_block: label. The test
innodb.innodb-change-buffering-recovery will be removed, because
due to this change, we will be unable to evict the desired page.
mtr_t::lock_register(): Register a change of a page latch
on an unmodified buffer-fixed block.
mtr_t::x_latch_at_savepoint(), mtr_t::sx_latch_at_savepoint():
Replaced by the use of mtr_t::upgrade_buffer_fix(), which now
also handles RW_S_LATCH.
mtr_t::set_modified(): For temporary tables, invoke
buf_page_t::set_modified() here and not in mtr_t::commit().
We will never set the MTR_MEMO_MODIFY flag on other than
persistent data pages, nor set mtr_t::m_modifications when
temporary data pages are modified.
mtr_t::commit(): Only invoke the buf_flush_note_modification() loop
if persistent data pages were modified.
mtr_t::get_already_latched(): Look up a latched page in mtr_t::m_memo.
This avoids many redundant entries in mtr_t::m_memo, as well as
redundant calls to buf_page_get_gen() for blocks that had already
been looked up in a mini-transaction.
btr_get_latched_root(): Return a pointer to an already latched root page.
This replaces btr_root_block_get() in cases where the mini-transaction
has already latched the root page.
btr_page_get_parent(): Fetch a parent page that was already latched
in BTR_MODIFY_TREE, by invoking mtr_t::get_already_latched().
If needed, upgrade the root page U latch to X.
This avoids bloating mtr_t::m_memo as well as performing redundant
buf_pool.page_hash lookups. For non-QUICK CHECK TABLE as well as for
B-tree defragmentation, we will invoke btr_cur_search_to_nth_level().
btr_cur_search_to_nth_level(): This will only be used for non-leaf
(level>0) B-tree searches that were formerly named BTR_CONT_SEARCH_TREE
or BTR_CONT_MODIFY_TREE. In MDEV-29835, this function could be
removed altogether, or retained for the case of
CHECK TABLE without QUICK.
btr_cur_t::left_block: Remove. btr_pcur_move_backward_from_page()
can retrieve the left sibling from the end of mtr_t::m_memo.
btr_cur_t::open_leaf(): Some clean-up.
btr_cur_t::search_leaf(): Replaces btr_cur_search_to_nth_level()
for searches to level=0 (the leaf level). We will never release
parent page latches before acquiring leaf page latches. If we need to
temporarily release the level=1 page latch in the BTR_SEARCH_PREV or
BTR_MODIFY_PREV latch_mode, we will reposition the cursor on the
child node pointer so that we will land on the correct leaf page.
btr_cur_t::pessimistic_search_leaf(): Implement new BTR_MODIFY_TREE
latching logic in the case that page splits or merges will be needed.
The parent pages (and their siblings) should already be latched on
the first dive to the leaf and be present in mtr_t::m_memo; there
should be no need for BTR_CONT_MODIFY_TREE. This pre-latching almost
suffices; it must be revised in MDEV-29835 and work-arounds removed
for cases where mtr_t::get_already_latched() fails to find a block.
rtr_search_to_nth_level(): A SPATIAL INDEX version of
btr_search_to_nth_level() that can search to any level
(including the leaf level).
rtr_search_leaf(), rtr_insert_leaf(): Wrappers for
rtr_search_to_nth_level().
rtr_search(): Replaces rtr_pcur_open().
rtr_latch_leaves(): Replaces btr_cur_latch_leaves(). Note that unlike
in the B-tree code, there is no error handling in case the sibling
pages are corrupted.
rtr_cur_restore_position(): Remove an unused constant parameter.
btr_pcur_open_on_user_rec(): Remove the constant parameter
mode=PAGE_CUR_GE.
row_ins_clust_index_entry_low(): Use a new
mode=BTR_MODIFY_ROOT_AND_LEAF to gain access to the root page
when mode!=BTR_MODIFY_TREE, to write the PAGE_ROOT_AUTO_INC.
BTR_SEARCH_TREE, BTR_CONT_SEARCH_TREE: Remove.
BTR_CONT_MODIFY_TREE: Note that this is only used by
rtr_search_to_nth_level().
btr_pcur_optimistic_latch_leaves(): Replaces
btr_cur_optimistic_latch_leaves().
ibuf_delete_rec(): Acquire exclusive ibuf.index->lock in order
to avoid a deadlock with ibuf_insert_low(BTR_MODIFY_PREV).
btr_blob_log_check_t(): Acquire a U latch on the root page,
so that btr_page_alloc() in btr_store_big_rec_extern_fields()
will avoid a deadlock.
btr_store_big_rec_extern_fields(): Assert that the root page latch
is being held.
Tested by: Matthias Leich
Reviewed by: Vladislav Lesin
This also fixes part of MDEV-29835 Partial server freeze
which is caused by violations of the latching order that was
defined in https://dev.mysql.com/worklog/task/?id=6326
(WL#6326: InnoDB: fix index->lock contention). Unless the
current thread is holding an exclusive dict_index_t::lock,
it must acquire page latches in a strict parent-to-child,
left-to-right order. Not all cases are fixed yet. Failure to
follow the correct latching order will cause deadlocks of threads
due to lock order inversion.
As part of these changes, the BTR_MODIFY_TREE mode is modified
so that an Update latch (U a.k.a. SX) will be acquired on the
root page, and eXclusive latches (X) will be acquired on all pages
leading to the leaf page, as well as any left and right siblings
of the pages along the path. The test innodb.innodb_wl6326
will be removed, because at the time the DEBUG_SYNC point is hit,
the thread is actually holding several page latches that will be
blocking a concurrent SELECT statement.
We also remove double bookkeeping that was caused due to excessive
information hiding in mtr_t::m_memo. We simply let mtr_t::m_memo
store information of latched pages, and ensure that
mtr_memo_slot_t::object is never a null pointer.
The tree_blocks[] and tree_savepoints[] were redundant.
mtr_t::get_already_latched(): Look up a latched page in mtr_t::m_memo.
This avoids many redundant entries in mtr_t::m_memo, as well as
redundant calls to buf_page_get_gen() for blocks that had already
been looked up in a mini-transaction.
btr_get_latched_root(): Return a pointer to an already latched root page.
This replaces btr_root_block_get() in cases where the mini-transaction
has already latched the root page.
btr_page_get_parent(): Fetch a parent page that was already latched
in BTR_MODIFY_TREE, by invoking mtr_t::get_already_latched().
If needed, upgrade the root page U latch to X.
This avoids bloating mtr_t::m_memo as well as redundant
buf_pool.page_hash lookups. For non-QUICK CHECK TABLE as well as for
B-tree defragmentation, we will invoke btr_cur_search_to_nth_level().
btr_cur_search_to_nth_level(): This will only be used for non-leaf
(level>0) B-tree searches that were formerly named BTR_CONT_SEARCH_TREE
or BTR_CONT_MODIFY_TREE. In MDEV-29835, this function could be
removed altogether, or retained for the case of
CHECK TABLE without QUICK.
btr_cur_t::search_leaf(): Replaces btr_cur_search_to_nth_level()
for searches to level=0 (the leaf level).
btr_cur_t::pessimistic_search_leaf(): Implement the new
BTR_MODIFY_TREE latching logic in the case that page splits
or merges will be needed. The parent pages (and their siblings)
should already be latched on the first dive to the leaf and be
present in mtr_t::m_memo; there should be no need for
BTR_CONT_MODIFY_TREE. This pre-latching almost suffices;
MDEV-29835 will have to revise it and remove work-arounds where
mtr_t::get_already_latched() fails to find a block.
rtr_search_to_nth_level(): A SPATIAL INDEX version of
btr_search_to_nth_level() that can search to any level
(including the leaf level).
rtr_search_leaf(), rtr_insert_leaf(): Wrappers for
rtr_search_to_nth_level().
rtr_search(): Replaces rtr_pcur_open().
rtr_cur_restore_position(): Remove an unused constant parameter.
btr_pcur_open_on_user_rec(): Remove the constant parameter
mode=PAGE_CUR_GE.
btr_cur_latch_leaves(): Update a pre-existing mtr_t::m_memo entry
for the current leaf page.
row_ins_clust_index_entry_low(): Use a new
mode=BTR_MODIFY_ROOT_AND_LEAF to gain access to the root page
when mode!=BTR_MODIFY_TREE, to write the PAGE_ROOT_AUTO_INC.
btr_cur_t::open_leaf(): Some clean-up.
mtr_t::lock_register(): Register a page latch on a buffer-fixed block.
BTR_SEARCH_TREE, BTR_CONT_SEARCH_TREE: Remove.
BTR_CONT_MODIFY_TREE: Note that this is only used by
rtr_search_to_nth_level().
btr_pcur_optimistic_latch_leaves(): Replaces
btr_cur_optimistic_latch_leaves().
ibuf_delete_rec(): Acquire ibuf.index->lock.u_lock() in order
to avoid a deadlock with ibuf_insert_low(BTR_MODIFY_PREV).
Tested by: Matthias Leich
To avoid heap memory allocation overhead for mtr_t::m_memo,
we will allocate a small number of elements statically in
mtr_t::m_memo::small. Only if that preallocated data is
insufficient, we will invoke my_alloc() or my_realloc() for
more storage. The implementation of the data structure is
inspired by llvm::SmallVector.
