The InnoDB insert buffer was upgraded in MySQL 5.5 into a change
buffer that also covers delete-mark and delete (purge) operations.
There is an important constraint for delete operations: a B-tree
leaf page must not become empty unless the entire tree becomes empty,
consisting of an empty root page. Because change buffer merges only
occur on a single leaf page at a time, delete operations must not be
buffered if it is possible that the last record of the page could be
deleted. (In that case, we would refuse to use the change buffer, and
if we really delete the last record, we would shrink the index tree.)
The function ibuf_get_volume_buffered_hash() is part of our insurance
that the page would not become empty. It is supposed to map each
buffered INSERT or DELETE_MARK record payload into a hash value.
We will only count each such record as a distinct key if there is no
hash collision. DELETE operations will always decrement the predicted
number fo records in the page.
Due to a bug in the function, we would actually compute the hash value
not only on the record payload, but also on some following bytes,
in case the record contains NULL values. In MySQL Bug #61104, we had
some examples of this dating back to 2012. But back then, we failed to
reproduce the bug, and in commit d84c95579b
we simply demoted the hard assertion to a message printout and a debug
assertion failure.
ibuf_get_volume_buffered_hash(): Correctly compute the hash value
of the payload bytes only. Note: we will consider
('foo','bar'),(NULL,'foobar'),('foob','ar') to be equal, but this
is not a problem, because in case of a hash collision, we could
also consider ('boo','far') to be equal, and underestimate the number
of records in the page, leading to refusing to buffer a DELETE.
In my micro-benchmarks memcmp(4196) 3 times faster than old
implementation. Also, it's generally better to use as less
reinterpret_casts<> as possible.
buf_is_zeroes(): renamed from buf_page_is_zeroes() and
argument changed to span<> for convenience.
st_::span<T>::const_iterator: fixed
page_zip-verify_checksum(): make argument byte* instead of void*
offset_t: this is a type which represents one record offset.
It's unsigned short int.
a lot of functions: replace ulint with offset_t
btr_pcur_restore_position_func(),
page_validate(),
row_ins_scan_sec_index_for_duplicate(),
row_upd_clust_rec_by_insert_inherit_func(),
row_vers_impl_x_locked_low(),
trx_undo_prev_version_build():
allocate record offsets on the stack instead of waiting for rec_get_offsets()
to allocate it from mem_heap_t. So, reducing memory allocations.
RECORD_OFFSET, INDEX_OFFSET:
now it's less convenient to store pointers in offset_t*
array. One pointer occupies now several offset_t. And those constant are start
indexes into array to places where to store pointer values
REC_OFFS_HEADER_SIZE: adjusted for the new reality
REC_OFFS_NORMAL_SIZE:
increase size from 100 to 300 which means less heap allocations.
And sizeof(offset_t[REC_OFFS_NORMAL_SIZE]) now is 600 bytes which
is smaller than previous 800 bytes.
REC_OFFS_SEC_INDEX_SIZE: adjusted for the new reality
rem0rec.h, rem0rec.ic, rem0rec.cc:
various arguments, return values and local variables types were changed to
fix numerous integer conversions issues.
enum field_type_t:
offset types concept was introduces which replaces old offset flags stuff.
Like in earlier version, 2 upper bits are used to store offset type.
And this enum represents those types.
REC_OFFS_SQL_NULL, REC_OFFS_MASK: removed
get_type(), set_type(), get_value(), combine():
these are convenience functions to work with offsets and it's types
rec_offs_base()[0]:
still uses an old scheme with flags REC_OFFS_COMPACT and REC_OFFS_EXTERNAL
rec_offs_base()[i]:
these have type offset_t now. Two upper bits contains type.
As noted in commit abd45cdc38
a search with PAGE_CUR_GE may land on the supremum record on
a leaf page that is not the rightmost leaf page. This could occur
when all keys on the current page are smaller than the search key,
and the smallest key on the successor page is larger than the search key.
Hence, after a failed PAGE_CUR_GE search, assertions
btr_pcur_is_after_last_in_tree() are bogus
and should be replaced with btr_pcur_is_after_last_on_page().
buf_read_ibuf_merge_pages(): Discard any page numbers that are
outside the current bounds of the tablespace, by invoking the
function ibuf_delete_recs() that was introduced in MDEV-20934.
This could avoid an infinite change buffer merge loop on
innodb_fast_shutdown=0, because normally the change buffer merge
would only be attempted if a page was successfully loaded into
the buffer pool.
dict_drop_index_tree(): Add the parameter trx_t*.
To prevent the DROP TABLE crash, do not invoke btr_free_if_exists()
if the entire .ibd file will be dropped. Thus, we will avoid a crash
if the BTR_SEG_LEAF or BTR_SEG_TOP of the index is corrupted,
and we will also avoid unnecessarily accessing the to-be-dropped
tablespace via the buffer pool.
In MariaDB 10.2, we disable the DROP TABLE fix if innodb_safe_truncate=0,
because the backup-unsafe MySQL 5.7 WL#6501 form of TRUNCATE TABLE
requires that the individual pages be freed inside the tablespace.
Apart from page latches (buf_block_t::lock), mini-transactions
are keeping track of at most one dict_index_t::lock and
fil_space_t::latch at a time, and in a rare case, purge_sys.latch.
Let us introduce interfaces for acquiring an index latch
or a tablespace latch.
In a later version, we may want to introduce mtr_t members
for holding a latched dict_index_t* and fil_space_t*,
and replace the remaining use of mtr_t::m_memo
with std::set<buf_block_t*> or with a map<buf_block_t*,byte*>
pointing to log records.
A search with PAGE_CUR_GE may land on the supremum record on
a leaf page that is not the rightmost leaf page.
This could occur when all keys on the current page are
smaller than the search key, and the smallest key on the
successor page is larger than the search key.
ibuf_delete_recs(): Correct the debug assertion accordingly.
Due to a data corruption bug that may have occurred a long time earlier
(possibly involving physical backup and MySQL Bug #69122, which was
addressed in commit f166ec71b7)
it seems possible that the InnoDB change buffer might end up containing
entries, while no buffered changes exist according to the change buffer
bitmap pages in the .ibd files.
ibuf_delete_recs(): New function, to be invoked on slow shutdown only.
Remove all buffered changes for a specific page.
ibuf_merge_or_delete_for_page(): If the change buffer bitmap is clean
and a slow shutdown is in progress, invoke ibuf_delete_recs().
We do not want to do that during normal operation, due to the additional
overhead that is involved. The bitmap page should be consistent with
the change buffer in the first place.
To diagnose a hang in slow shutdown (innodb_fast_shutdown=0),
let us introduce a Boolean startup option in debug builds
that will cause the contents of the InnoDB change buffer
to be dumped to the server error log at startup.
Until now, InnoDB inefficiently compared the aligned fields
FIL_PAGE_PREV, FIL_PAGE_NEXT to the byte-order-agnostic value FIL_NULL.
This is a backport of 32170f8c6d
from MariaDB Server 10.3.
In MariaDB 10.4.0, commit 09af00cbde
removed the crash-upgrade logic for the MariaDB 10.2
innodb_safe_truncate=OFF TRUNCATE TABLE (which was the only option
between MariaDB 10.2.2 and 10.2.18), but failed to adjust some
comments and code.
buf_page_io_complete(): Remove a bogus comment about TRUNCATE.
dict_recreate_index_tree(): Unused function; remove.
fil_space_t::stop_new_ops: Clarify the comment.
fil_space_acquire_low(): Remove a bogus comment about TRUNCATE.
fil_check_pending_ops(), fil_check_pending_io(): Adjust a warning message.
This code is only invoked as part of DISCARD TABLESPACE or DROP TABLE.
DROP TABLE is internally used as part of ALTER TABLE, OPTIMIZE TABLE,
or TRUNCATE TABLE.
RemoteDatafile::create_link_file(): Clarify a comment.
ibuf_delete_for_discarded_space(): Clarify the function comment.
dict_table_x_lock_indexes(), dict_table_x_unlock_indexes():
Merge with the only remaining caller, row_quiesce_set_state().
page_create_zip(): Remove a bogus comment about TRUNCATE.
The setting innodb_change_buffering_debug=2 was supposed to inject
a crash during change buffer merge. There is no public test for
that functionality, and even if there were, it would be better
to use DEBUG_SYNC to halt the thread that does change buffer merge,
force a redo log flush from another thread, and finally kill the
server externally.
- Introduce a new variable called innodb_encrypt_temporary_tables which is
a boolean variable. It decides whether to encrypt the temporary tablespace.
- Encrypts the temporary tablespace based on full checksum format.
- Introduced a new counter to track encrypted and decrypted temporary
tablespace pages.
- Warnings issued if temporary table creation has conflict value with
innodb_encrypt_temporary_tables
- Added a new test case which reads and writes the pages from/to temporary
tablespace.
