For the adaptive hash index, dtuple_fold() and rec_fold() were employing
a slow rolling hash algorithm, computing hash values ("fold") for one
field and one byte at a time, while depending on calls to
rec_get_offsets().
We already have optimized implementations of CRC-32C and have been
successfully using that function in some other InnoDB tables, but not
yet in the adaptive hash index.
Any linear function such as any CRC will fail the avalanche test that
any cryptographically secure hash function is expected to pass:
any single-bit change in the input key should affect on average half
the bits in the output.
But we always were happy with less than cryptographically secure:
in fact, ut_fold_ulint_pair() or ut_fold_binary() are just about as
linear as any CRC, using a combination of multiplication and addition,
partly carry-less. It is worth noting that exclusive-or corresponds to
carry-less subtraction or addition in a binary Galois field, or GF(2).
We only need some way of reducing key prefixes into hash values.
The CRC-32C should be better than a Rabin–Karp rolling hash algorithm.
Compared to the old hash algorithm, it has the drawback that there will
be only 32 bits of entropy before we choose the hash table cell by a
modulus operation. The size of each adaptive hash index array is
(innodb_buffer_pool_size / 512) / innodb_adaptive_hash_index_parts.
With the maximum number of partitions (512), we would not exceed 1<<32
elements per array until the buffer pool size exceeds 1<<50 bytes (1 PiB).
We would hit other limits before that: the virtual address space on many
contemporary 64-bit processor implementations is only 48 bits (256 TiB).
So, we can simply go for the SIMD accelerated CRC-32C.
rec_fold(): Take a combined parameter n_bytes_fields. Determine the
length of each field on the fly, and compute CRC-32C over a single
contiguous range of bytes, from the start of the record payload area
to the end of the last full or partial field. For secondary index records
in ROW_FORMAT=REDUNDANT, also the data area that is reserved for NULL
values (to facilitate in-place updates between NULL and NOT NULL values)
will be included in the count. Luckily, InnoDB always zero-initialized
such unused area; refer to data_write_sql_null() in
rec_convert_dtuple_to_rec_old(). For other than ROW_FORMAT=REDUNDANT,
no space is allocated for NULL values, and therefore the CRC-32C will
only cover the actual payload of the key prefix.
dtuple_fold(): For ROW_FORMAT=REDUNDANT, include the dummy NULL values
in the CRC-32C, so that the values will be comparable with rec_fold().
innodb_ahi-t: A unit test for rec_fold() and dtuple_fold().
btr_search_build_page_hash_index(), btr_search_drop_page_hash_index():
Use a fixed-size stack buffer for computing the fold values, to avoid
dynamic memory allocation.
btr_search_drop_page_hash_index(): Do not release part.latch if we
need to invoke multiple batches of rec_fold().
dtuple_t: Allocate fewer bits for the fields. The maximum number of
data fields is about 1023, so uint16_t will be fine for them. The
info_bits is stored in less than 1 byte.
ut_pair_min(), ut_pair_cmp(): Remove. We can actually combine and compare
int(n_fields << 16 | n_bytes).
PAGE_CUR_LE_OR_EXTENDS, PAGE_CUR_DBG: Remove. These were never defined,
because they would only work with latin1_swedish_ci if at all.
btr_cur_t::check_mismatch(): Replaces !btr_search_check_guess().
cmp_dtuple_rec_bytes(): Replaces cmp_dtuple_rec_with_match_bytes().
Determine the offsets of fields on the fly.
page_cur_try_search_shortcut_bytes(): This caller of
cmp_dtuple_rec_bytes() will not be invoked on the change buffer tree.
cmp_dtuple_rec_leaf(): Replaces cmp_dtuple_rec_with_match()
for comparing leaf-page records.
buf_block_t::ahi_left_bytes_fields: Consolidated Atomic_relaxed<uint32_t>
of curr_left_side << 31 | curr_n_bytes << 16 | curr_n_fields.
The other set of parameters (n_fields, n_bytes, left_side) was removed
as redundant.
btr_search_update_hash_node_on_insert(): Merged to
btr_search_update_hash_on_insert().
btr_search_build_page_hash_index(): Take combined left_bytes_fields
instead of n_fields, n_bytes, left_side.
btr_search_update_block_hash_info(), btr_search_update_hash_ref():
Merged to btr_search_info_update_hash().
btr_cur_t::n_bytes_fields: Replaces n_bytes << 16 | n_fields.
We also remove many redundant checks of btr_search.enabled.
If we are holding any btr_sea::partition::latch, then a nonnull pointer
in buf_block_t::index must imply that the adaptive hash index is enabled.
Reviewed by: Vladislav Lesin
Let us use implement a simple fixed-size allocator for the adaptive hash
index, insted of complicating mem_heap_t or mem_block_info_t.
MEM_HEAP_BTR_SEARCH: Remove.
mem_block_info_t::free_block(), mem_heap_free_block_free(): Remove.
mem_heap_free_top(), mem_heap_get_top(): Remove.
btr_sea::partition::spare: Replaces mem_block_info_t::free_block.
This keeps one spare block per adaptive hash index partition, to
process an insert.
We must not wait for buf_pool.mutex while holding
any btr_sea::partition::latch. That is why we cache one block for
future allocations. This is protected by a new
btr_sea::partition::blocks_mutex in order to relieve pressure on
btr_sea::partition::latch.
btr_sea::partition::prepare_insert(): Replaces
btr_search_check_free_space_in_heap().
btr_sea::partition::erase(): Replaces ha_search_and_delete_if_found().
btr_sea::partition::cleanup_after_erase(): Replaces the most part of
ha_delete_hash_node(). Unlike the previous implementation, we will
retain a spare block for prepare_insert().
This should reduce some contention on buf_pool.mutex.
btr_search.n_parts: Replaces btr_ahi_parts.
btr_search.enabled: Replaces btr_search_enabled. This must hold
whenever buf_block_t::index is set while a thread is holding a
btr_sea::partition::latch.
dict_index_t::search_info: Remove pointer indirection, and use
Atomic_relaxed or Atomic_counter for most fields.
btr_search_guess_on_hash(): Let the caller ensure that latch_mode is
BTR_MODIFY_LEAF or BTR_SEARCH_LEAF. Release btr_sea::partition::latch
before buffer-fixing the block. The page latch that we already acquired
is preventing buffer pool eviction. We must validate both
block->index and block->page.state while holding part.latch
in order to avoid race conditions with buffer page relocation
or buf_pool_t::resize().
btr_search_check_guess(): Remove the constant parameter
can_only_compare_to_cursor_rec=false.
ahi_node: Replaces ha_node_t.
This has been tested by running the regression test suite
with the adaptive hash index enabled:
./mtr --mysqld=--loose-innodb-adaptive-hash-index=ON
Reviewed by: Vladislav Lesin
When srv_page_size and innodb_page_size were introduced,
the functions page_align() and page_offset() got more expensive.
Let us try to replace such calls with simpler pointer arithmetics
with respect to the buffer page frame.
page_rec_get_next_non_del_marked(): Add a page frame as a parameter,
and template<bool comp>.
page_rec_next_get(): A more efficient variant of page_rec_get_next(),
with template<bool comp> and const page_t* parameters.
lock_get_heap_no(): Replaces page_rec_get_heap_no() outside debug checks.
fseg_free_step(), fseg_free_step_not_header(): Take the header block
as a parameter.
Reviewed by: Vladislav Lesin
btr_cur_t::search_leaf(): When the index root page is also a leaf page,
we may need to upgrade our existing shared root page latch into an
exclusive latch. Even if we end up waiting, the root page won't be able
to go away while we hold an index()->lock. The index page may be split;
that is all.
btr_latch_prev(): Acquire the page latch while holding a buffer-fix
and an index tree latch. Merge the change buffer if needed. Use
buf_pool_t::page_fix() for this special case instead of complicating
buf_page_get_low() and buf_page_get_gen().
row_merge_read_clustered_index(): Remove some code that does not seem
to be useful. No difference was observed with regard to removing this
code when a CREATE INDEX or OPTIMIZE TABLE statement was run concurrently
with sysbench oltp_update_index --tables=1 --table_size=1000 --threads=16.
buf_pool_t::unzip(): Decompress a ROW_FORMAT=COMPRESSED page.
buf_pool_t::page_fix(): Handle also ROW_FORMAT=COMPRESSED pages
as well as change buffer merge. Optionally return an error.
Add a flag for suppressing a page latch wait and a special return
value -1 to indicate that the call would block.
This is the preferred way of buffer-fixing blocks.
The functions buf_page_get_gen() and buf_page_get_low() are only being
invoked with rw_latch=RW_NO_LATCH in operations on SPATIAL INDEX.
buf_page_t: Define some static functions for interpreting state().
buf_page_get_zip(), buf_read_page(),
buf_read_ahead_random(), buf_read_ahead_linear():
Remove the redundant parameter zip_size. We must look up the
tablespace and can invoke fil_space_t::zip_size() on it.
buf_page_get_low(): Require mtr!=nullptr.
buf_page_get_gen(): Implement some lock downgrading during recovery.
ibuf_page_low(): Use buf_pool_t::page_fix() in a debug check.
We do wait for a page read here, because otherwise a debug assertion in
buf_page_get_low() in the test innodb.ibuf_delete could occasionally fail.
PageConverter::operator(): Invoke buf_pool_t::page_fix() in order
to possibly evict a block. This allows us to remove some
special case code from buf_page_get_low().
In the merge commit f9807aadef
there were some omissions or errors.
ibuf_remove_free_page(): Return an error if the free list is corrupted
when removing the change buffer on an upgrade. A special 11.0 version of
commit 263932d505 would have been useful.
buf_page_get_gen(): Correctly handle the case that a page was being
concurrently read into the buffer pool and found out to be corrupted.
This was part of commit a4cda66e2d
but had been discarded in the merge.
Because MariaDB Server 11.0 has reached its end of life as of
commit 466ae1cf81 this fix is being applied
to the 11.1 branch.
ibuf_remove_free_page(): Correct the calculation of root_savepoint().
The first entry acquired by ibuf_tree_root_get() will be ibuf.index.lock
and not the change buffer root page.
Thanks to Matthias Leich for finding this bug in RQG.
Unfortunately, this code is very difficult to cover
in our regression test suite.
When the change buffer records for a page span across multiple change
buffer leaf pages or the starting record is at the beginning of a page
with a left sibling, ibuf_delete_recs deletes only the records in first
page and fails to move to subsequent pages.
Subsequently a slow shutdown hangs trying to delete those left over
records.
Fix-A: Position the cursor to an user record in B-tree and exit only
when all records are exhausted.
Fix-B: Make sure we call ibuf_delete_recs during slow shutdown for
pages with IBUF entries to cleanup any previously left over records.
Issue:
------
The actual order of acquisition of the IBUF pessimistic insert mutex
(SYNC_IBUF_PESS_INSERT_MUTEX) and IBUF header page latch
(SYNC_IBUF_HEADER) w.r.t space latch (SYNC_FSP) differs from the order
defined in sync0types.h. It was not discovered earlier as the path to
ibuf_remove_free_page was not covered by the mtr test. Ideal order and
one defined in sync0types.h is as follows.
SYNC_IBUF_HEADER -> SYNC_IBUF_PESS_INSERT_MUTEX -> SYNC_FSP
In ibuf_remove_free_page, we acquire space latch earlier and we have
the order as follows resulting in the assert with innodb_sync_debug=on.
SYNC_FSP -> SYNC_IBUF_HEADER -> SYNC_IBUF_PESS_INSERT_MUTEX
Fix:
---
We do maintain this order in other places and there doesn't seem to be
any real issue here. To reduce impact in GA versions, we avoid doing
extensive changes in mutex ordering to match the current
SYNC_IBUF_PESS_INSERT_MUTEX order. Instead we relax the ordering check
for IBUF pessimistic insert mutex using SYNC_NO_ORDER_CHECK.
flst_read_addr(): Remove assertions. Instead, we will check these
conditions in the callers and avoid a crash in case of corruption.
We will check the conditions more carefully, because the callers
know more exact bounds for the page numbers and the byte offsets
withing pages.
flst_remove(), flst_add_first(), flst_add_last(): Add a parameter
for passing fil_space_t::free_limit. None of the lists may point to
pages that are beyond the current initialized length of the
tablespace.
trx_rseg_mem_restore(): Access the first page of the tablespace,
so that we will correctly recover rseg->space->free_limit
in case some log based recovery is pending.
ibuf_remove_free_page(): Only look up the root page once, and
validate the last page number.
Reviewed by: Debarun Banerjee
The linear read-ahead (enabled by nonzero innodb_read_ahead_threshold)
works best if index leaf pages or undo log pages have been allocated
on adjacent page numbers. The read-ahead is assumed not to be helpful
in other types of page accesses, such as non-leaf index pages.
buf_page_get_low(): Do not invoke buf_page_t::set_accessed(),
buf_page_make_young_if_needed(), or buf_read_ahead_linear().
We will invoke them in those callers of buf_page_get_gen() or
buf_page_get() where it makes sense: the access is not
one-time-on-startup and the page and not going to be freed soon.
btr_copy_blob_prefix(), btr_pcur_move_to_next_page(),
trx_undo_get_prev_rec_from_prev_page(),
trx_undo_get_first_rec(), btr_cur_t::search_leaf(),
btr_cur_t::open_leaf(): Invoke buf_read_ahead_linear().
We will not invoke linear read-ahead in functions that would
essentially allocate or free pages, because pages that are
freshly allocated are expected to be initialized by buf_page_create()
and not read from the data file. Likewise, freeing pages should
not involve accessing any sibling pages, except for freeing
singly-linked lists of BLOB pages.
We will not invoke read-ahead in btr_cur_t::pessimistic_search_leaf()
or in a pessimistic operation of btr_cur_t::open_leaf(), because
it is assumed that pessimistic operations should be preceded by
optimistic operations, which should already have invoked read-ahead.
buf_page_make_young_if_needed(): Invoke also buf_page_t::set_accessed()
and return the result.
btr_cur_nonleaf_make_young(): Like buf_page_make_young_if_needed(),
but do not invoke buf_page_t::set_accessed().
Reviewed by: Vladislav Lesin
Tested by: Matthias Leich
buf_page_get_low(): Rename to buf_page_get_gen(), and assume that no
crash recovery is needed.
recv_sys_t::recover(): Replaces the old buf_page_get_gen(). Read a page
while crash recovery is in progress.
trx_rseg_get_n_undo_tablespaces(), ibuf_upgrade_needed():
Invoke recv_sys.recover() instead of buf_page_get_gen().
dict_boot(): Invoke recv_sys.recover() instead of buf_page_get_gen().
Do not load the system tables.
srv_start(): Load the system tables and the undo logs after all redo log
has been applied in recv_sys.apply(true) and we can safely invoke the
regular buf_page_get_gen().
ibuf_bitmap_buffered(): A new predicate, to check if the
IBUF_BITMAP_BUFFERED bit for a particular page is set.
ibuf_merge(): If ibuf_bitmap_buffered() does not hold,
skip the records for the page. One reason why we might have
this situation is the bug that was fixed in
commit 34c283ba1b (MDEV-32132).
dtype_new_read_for_order_and_null_size(): Correctly assign type->prtype.
This caused the fatal error and crash.
ibuf_merge(): Relax a too strict condition that would result in
[ERROR] InnoDB: Unable to upgrade the change buffer
when there exist buffered changes to redundant secondary indexes, such as
PRIMARY KEY(x), INDEX(x).
ibuf_upgrade(): Modify at most one user tablespace per mini-transaction,
to be crash-safe.
page_cur_insert_rec_zip(), page_cur_delete_rec(): Relax debug assertions
for ibuf_upgrade().
ibuf_log_rebuild_if_needed(): Invoke recv_sys.debug_free() only after
srv_log_rebuild_if_needed() to avoid an assertion failure. This code
is executed when the innodb_log_file_size is changed when upgrading
from 10.x to 11.0.
Tested by: Matthias Leich, Christian Hesse
When InnoDB attempts to buffer a change operation of a secondary index
leaf page (to insert, delete-mark or remove a record) and the
change buffer is too large, InnoDB used to trigger a change buffer merge
that could affect any tables. This could lead to huge variance in
system throughput and potentially unpredictable crashes, in case the
change buffer was corrupted and a crash occurred while attempting to
merge changes to a table that is not being accessed by the current
SQL statement.
ibuf_insert_low(): Simply return DB_STRONG_FAIL when the maximum size
of the change buffer is exceeded.
ibuf_contract_after_insert(): Remove.
ibuf_get_merge_page_nos_func(): Remove a constant parameter.
The function ibuf_contract() will be our only caller, during
shutdown with innodb_fast_shutdown=0.
A 3-thread deadlock has been frequently observed when using
innodb_change_buffering!=none and innodb_file_per_table=0:
(1) ibuf_merge_or_delete_for_page() holding an exclusive latch on the block
and waiting for an exclusive tablespace latch in fseg_page_is_allocated()
(2) btr_free_but_not_root() in fseg_free_step() waiting for an
exclusive tablespace latch
(3) fsp_alloc_free_page() holding the exclusive tablespace latch and waiting
for a latch on the block, which it is reallocating for something else
While this was reproduced using innodb_file_per_table=0, this hang should
be theoretically possible in .ibd files as well, when the recovery or
cleanup of a failed DROP INDEX or ADD INDEX is executing concurrently
with something that involves page allocation.
ibuf_merge_or_delete_for_page(): Avoid invoking fseg_page_is_allocated()
when block==nullptr. The call was redundant in this case, and it could
cause deadlocks due to latching order violation.
ibuf_read_merge_pages(): Acquire an exclusive tablespace latch
before invoking buf_page_get_gen(), which may cause
fseg_page_is_allocated() to be invoked in ibuf_merge_or_delete_for_page().
Note: This will not fix all latching order violations in this area!
Deadlocks involving ibuf_merge_or_delete_for_page(block!=nullptr) are
still possible if the caller is not acquiring an exclusive tablespace latch
upfront. This would be the case in any read operation that involves a
change buffer merge, such as SELECT, CHECK TABLE, or any DML operation that
cannot be buffered in the change buffer.
While downgrades are not supported and misguided attempts at it could
cause serious corruption especially after
commit b07920b634
it might be useful if InnoDB would start up even after an upgrade to
MariaDB Server 11.0 or later had removed the change buffer.
innodb_change_buffering_update(): Disallow anything else than
innodb_change_buffering=none when the change buffer is corrupted.
ibuf_init_at_db_start(): Mention a possible downgrade in the corruption
error message. If innodb_change_buffering=none, ignore the error but do
not initialize ibuf.index.
ibuf_free_excess_pages(), ibuf_contract(), ibuf_merge_space(),
ibuf_update_max_tablespace_id(), ibuf_delete_for_discarded_space(),
ibuf_print(): Check for !ibuf.index.
ibuf_check_bitmap_on_import(): Remove some unnecessary code.
This function is only accessing change buffer bitmap pages in a
data file that is not attached to the rest of the database.
It is not accessing the change buffer tree itself, hence it does
not need any additional mutex protection.
This has been tested both by starting up MariaDB Server 10.8 on
a 11.0 data directory, and by running ./mtr --big-test while
ibuf_init_at_db_start() was tweaked to always fail.
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
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
