Write log header just ones when file is created, instead of
writing to it on every log file wrap around.
log_t::file::write_header_durable(): this one writes to log header
log_write_buf(): this one stops writing to log header
By default, when redo log is being written for modifying a persistent
data page, the data page must actually be changed. If the write can
sometimes be optimized away, then the template parameter w=mtr_t::OPT
should be passed in order to silence the debug assertion failure.
InnoDB undo log pages can be reused without properly freeing or
initializing them in between. In particular, the undo log header
page field TRX_UNDO_TRX_NO could have been part of an undo log
record page, and those bytes could accidentally have the desired
value when the page is reused as an undo log header page of
another transaction.
Because the function trx_undo_set_state_at_finish() always changes
the TRX_UNDO_STATE of the page, and because recovery is only reading
TRX_UNDO_TRX_NO for pages that either have the correct TRX_UNDO_STATE
or, in trx_rseg_array_init(), are attached to the TRX_SYS page, the
garbage values in TRX_UNDO_TRX_NO do not seem to cause a problem.
This assertion failure affects debug builds only.
e.g.
- dont -> don't
- occurence -> occurrence
- succesfully -> successfully
- easyly -> easily
Also remove trailing space in selected files.
These changes span:
- server core
- Connect and Innobase storage engine code
- OQgraph, Sphinx and TokuDB storage engines
Related to MDEV-21769.
Instrument new synchronization primitive with thd_wait_begin/end
to inform threadpool about waits.
This considerably improve performance on write benchmarks
(e.g sysbench update_index) with generic threadpool, of course the cost is
possibility of many newly created threads.
Lifted long standing limitation to the XA of rolling it back at the
transaction's
connection close even if the XA is prepared.
Prepared XA-transaction is made to sustain connection close or server
restart.
The patch consists of
- binary logging extension to write prepared XA part of
transaction signified with
its XID in a new XA_prepare_log_event. The concusion part -
with Commit or Rollback decision - is logged separately as
Query_log_event.
That is in the binlog the XA consists of two separate group of
events.
That makes the whole XA possibly interweaving in binlog with
other XA:s or regular transaction but with no harm to
replication and data consistency.
Gtid_log_event receives two more flags to identify which of the
two XA phases of the transaction it represents. With either flag
set also XID info is added to the event.
When binlog is ON on the server XID::formatID is
constrained to 4 bytes.
- engines are made aware of the server policy to keep up user
prepared XA:s so they (Innodb, rocksdb) don't roll them back
anymore at their disconnect methods.
- slave applier is refined to cope with two phase logged XA:s
including parallel modes of execution.
This patch does not address crash-safe logging of the new events which
is being addressed by MDEV-21469.
CORNER CASES: read-only, pure myisam, binlog-*, @@skip_log_bin, etc
Are addressed along the following policies.
1. The read-only at reconnect marks XID to fail for future
completion with ER_XA_RBROLLBACK.
2. binlog-* filtered XA when it changes engine data is regarded as
loggable even when nothing got cached for binlog. An empty
XA-prepare group is recorded. Consequent Commit-or-Rollback
succeeds in the Engine(s) as well as recorded into binlog.
3. The same applies to the non-transactional engine XA.
4. @@skip_log_bin=OFF does not record anything at XA-prepare
(obviously), but the completion event is recorded into binlog to
admit inconsistency with slave.
The following actions are taken by the patch.
At XA-prepare:
when empty binlog cache - don't do anything to binlog if RO,
otherwise write empty XA_prepare (assert(binlog-filter case)).
At Disconnect:
when Prepared && RO (=> no binlogging was done)
set Xid_cache_element::error := ER_XA_RBROLLBACK
*keep* XID in the cache, and rollback the transaction.
At XA-"complete":
Discover the error, if any don't binlog the "complete",
return the error to the user.
Kudos
-----
Alexey Botchkov took to drive this work initially.
Sergei Golubchik, Sergei Petrunja, Marko Mäkelä provided a number of
good recommendations.
Sergei Voitovich made a magnificent review and improvements to the code.
They all deserve a bunch of thanks for making this work done!
1. Refactored innobase_close_connection(). Transaction must've already
been rolled back by this time. We should expect only transactions in the
PREPARED state when MDEV-742 is done.
2. Added missing put_pins() to trx_disconnect_prepared(). Missing
put_pins() wasn't a problem because trx_disconnect_prepared() is a dead
code. But it will get revived in the main MDEV-742 patch.
3. Fixed missing reset of trx->mysql_log_file_name when RW transaction
didn't emit any log records (zero-modification RW). The problem was
detected by ASAN when disconnected XA transaction was trying to make
use of inherited mysql_log_file_name pointing into binlog data of
detached THD.
This missing reset also had user-visible side effect, when
trx_sys_print_mysql_binlog_offset() would report binlog position
not of the most recently committed transaction.
One of possible scenarios that is expected to misbehave is as following:
thr1> CREATE TABLE t1(a INT) ENGINE=InnoDB;
thr1> INSERT INTO t1 VALUES(1);
thr1> BEGIN;
thr1> UPDATE t1 SET a=1
thr1> COMMIT; -- zero-modification, misses to reset mysql_log_file_name
thr2> BEGIN;
thr2> INSERT INTO t1 VALUES(2);
thr2> COMMIT;
thr1> BEGIN;
thr1> do-some-real-changes;
thr1> ROLLBACK; -- will store binlog pos from previous COMMIT in thr1?
In this case it means if binlog is replayed from position reported by
trx_sys_print_mysql_binlog_offset(), t1 will end up with two records
containing '2'.
Part of
MDEV-742 - XA PREPAREd transaction survive disconnect/server restart
myrg_open(): Reduce the scope of the variable 'end' and
simplify the code.
For some reason, I got no warning for this code in the 10.2
branch, only 10.3 or later.
The ENGINE=MERGE is covered by the tests main.merge, main.merge_debug,
and main.merge-big.
- This issue was caused by 5e62b6a5e0.
fts_optimize_callback() should free fts_optimize_wq and make it as NULL
when it receives FTS_MSG_STOP message. So that subsequent
fts_optimize_callback() doesn't fail with segmentation fault.
Starting with commit 1a6f708ec5
the function buf_pool_get_dirty_pages_count() is only used
in a debug check. It was dead code for non-debug builds.
buf_flush_dirty_pages(): Perform the debug check inline,
and replace the assertion
ut_ad(first || buf_pool_get_dirty_pages_count(id) == 0);
with another one that is executed while holding the mutexes:
ut_ad(id != bpage->id.space());
_ma_fetch_keypage(): Correct an assertion that used to always hold.
Thanks to clang -Wint-in-bool-context for flagging this.
double_to_datetime_with_warn(): Suppress -Wimplicit-int-float-conversion
by adding a cast. LONGLONG_MAX converted to double will actually be
LONGLONG_MAX+1.
All tablespace metadata is buffered in fil_system. There is a LRU
mechanism, but that only controls the opening and closing of
fil_node_t::handle.
It is much more efficient and less error-prone to access data file names
by looking up the fil_space_t object rather than by essentially joining
each row with an access to SYS_DATAFILES via the InnoDB internal SQL parser.
dict_get_first_path(): Declare static. The function may only be needed
when loading or updating the data dictionary. Also, change a condition
in order to avoid a bogus GCC 10 -Wstringop-overflow warning for
mem_strdupl() about len==ULINT_UNDEFINED.
i_s_sys_tablespaces_fill_table(): Do not access other InnoDB internal
dictionary tables than SYS_TABLESPACES.
The -Wconversion in GCC seems to be stricter than in clang.
GCC at least since version 4.4.7 issues truncation warnings for
assignments to bitfields, while clang 10 appears to only issue
warnings when the sizes in bytes rounded to the nearest integer
powers of 2 are different.
Before GCC 10.0.0, -Wconversion required more casts and would not
allow some operations, such as x<<=1 or x+=1 on a data type that
is narrower than int.
GCC 5 (but not GCC 4, GCC 6, or any later version) is complaining
about x|=y even when x and y are compatible types that are narrower
than int. Hence, we must rewrite some x|=y as
x=static_cast<byte>(x|y) or similar, or we must disable -Wconversion.
In GCC 6 and later, the warning for assigning wider to bitfields
that are narrower than 8, 16, or 32 bits can be suppressed by
applying a bitwise & with the exact bitmask of the bitfield.
For older GCC, we must disable -Wconversion for GCC 4 or 5 in such
cases.
The bitwise negation operator appears to promote short integers
to a wider type, and hence we must add explicit truncation casts
around them. Microsoft Visual C does not allow a static_cast to
truncate a constant, such as static_cast<byte>(1) truncating int.
Hence, we will use the constructor-style cast byte(~1) for such cases.
This has been tested at least with GCC 4.8.5, 5.4.0, 7.4.0, 9.2.1, 10.0.0,
clang 9.0.1, 10.0.0, and MSVC 14.22.27905 (Microsoft Visual Studio 2019)
on 64-bit and 32-bit targets (IA-32, AMD64, POWER 8, POWER 9, ARMv8).
The extension of the record comparison functions for SPATIAL INDEX in
mysql/mysql-server@b66ad511b6
was suboptimal for multiple reasons:
Some functions used unnecessary temporary variables of the int type,
instead of the more appropriate size_t, causing type mismatch.
Many functions unnecessarily required rec_get_offsets() to be
computed, or a parameter for length, although the size of the
minimum bounding rectangle (MBR) is hard-coded as
SPDIMS * 2 * sizeof(double), or 32 bytes.
In InnoDB SPATIAL INDEX records, there always is a 32-byte key
followed by either a 4-byte child page number or the PRIMARY KEY value.
The length parameters were not properly validated.
The function cmp_geometry_field() was making an incorrect attempt
at checking that the lengths are at least sizeof(double) (8 bytes),
even though the function is accessing up to 32 bytes in both MBR.
Functions that are called from only one compilation unit are defined
in another compilation unit, making the code harder to follow and
potentially slower to execute.
cmp_dtuple_rec_with_gis(): FIXME: Correct the debug assertion
and possibly the function TABLE_SHARE::init_from_binary_frm_image()
or related code, which causes an unexpected length of
DATA_MBR_LEN + 2 bytes to be passed to this function.
actually, page_zip_verify_checksum() generally allows all-zeroes
checksums because our CRC32 checksum is something like
crc_1 ^ crc_2 ^ crc_3
Also, all zeroes page is considered correct.
As a side effect fix nasty reinterpret_cast<> UB
Also, since c0f47a4a58 innodb_checksum_algorithm=full_crc32
exists which computes CRC32 in one go (without bitwise arithmetic)
PageBulk::insertPage(): Check the array bounds before comparing.
We used to read one byte beyond the end of the 'rec' payload.
The incorrect logic was originally introduced in
commit 7ae21b18a6.
buf_flush_freed_page(): Reformat in the common style, and
simplify some code. Prefer to request all information from
smaller data structures (buf_page_t) than from fil_space_t
or the global variable srv_immediate_scrub_data_uncompressed.
SysTablespace::open_or_create(): Assert that the temporary
tablespace will not be created in page_compressed format, so that
buf_flush_freed_page() can avoid checking that on every call.
IORequest: Remove duplicated constructors, and do not explicitly
declare a default constructor.
The following parameters are deprecated:
innodb-background-scrub-data-uncompressed
innodb-background-scrub-data-compressed
innodb-background-scrub-data-interval
innodb-background-scrub-data-check-interval
Removed scrubbing code completely(btr0scrub.h, btr0scrub.cc)
Removed information_schema.innodb_tablespaces_scrubbing tables
Removed the scrubbing logic from fil_crypt_thread()
When a InnoDB data file page is freed, its contents becomes garbage,
and any storage allocated in the data file is wasted. During flushing,
InnoDB initializes the page with zeros if scrubbing is enabled. If the
tablespace is compressed then InnoDB should punch a hole else ignore the
flushing of the freed page.
buf_page_t:
- Replaced the variable file_page_was_freed, init_on_flush in buf_page_t
with status enum variable.
- Changed all debug assert of file_page_was_freed to DBUG_ASSERT
of buf_page_t::status
Removed buf_page_set_file_page_was_freed(),
buf_page_reset_file_page_was_freed().
buf_page_free(): Newly added function which takes X-lock on the page
before marking the status as FREED. So that InnoDB flush handler can
avoid concurrent flush of the freed page. Also while flushing the page,
InnoDB make sure that redo log which does freeing of the page also written
to the disk. Currently, this function only marks the page as FREED if
it is in buffer pool
buf_flush_freed_page(): Newly added function which initializes zeros
asynchorously if innodb_immediate_scrub_data_uncompressed is enabled.
Punch a hole to the file synchorously if page_compressed is enabled.
Reset the io_fix to NORMAL. Release the block from flush list and
associated mutex before writing zeros or punch a hole to the file.
buf_flush_page(): Removed the unnecessary usage of temporary
variable "flush"
fil_io(): Introduce new parameter called punch_hole. It allows fil_io()
to punch the hole to the file for the given offset.
buf_page_create(): Let the callers assign buf_page_t::status.
Every caller should eventually invoke mtr_t::init().
fsp_page_create(): Remove the unused mtr_t parameter.
In all other callers of buf_page_create() except fsp_page_create(),
before invoking mtr_t::init(), invoke
mtr_t::sx_latch_at_savepoint() or mtr_t::x_latch_at_savepoint().
mtr_t::init(): Initialize buf_page_t::status also for the temporary
tablespace (when redo logging is disabled), to avoid assertion failures.
The default keyread_time() was optimized for blocks and not suitable for
HEAP. The effect was the HEAP prefered table scans over ranges for btree
indexes.
Fixed also get_sweep_read_cost() for HEAP tables.
recv_log_recover_10_4(): Add a missing bit pattern negation that
was forgotten when commit f8a9f90667
(MDEV-12353) removed the support for crash-upgrading.
btr_cur_upd_rec_in_place(): Invoke page_zip_rec_set_deleted()
for ROW_FORMAT=COMPRESSED pages, so that the change will be
written to the redo log.
This part of crash recovery was broken in
commit 08ba388713 (MDEV-12353).
create_log_file(): Delete all old redo log files where they used to be
deleted, after the crash injection point innodb_log_abort_6,
before commit 9ef2d29ff4
deprecated and ignored the setting innodb_log_files_in_group.
log_crypt_101_read_checkpoint(), log_crypt_101_read_block():
Declare as ATTRIBUTE_COLD. These are only used when
checking that a MariaDB 10.1 encrypted redo log is clean.
log_block_calc_checksum_format_0(): Define in the only
compilation unit where it is needed. This is only used
when reading the checkpoint information from redo logs
before MariaDB 10.2.2.
crypt_info_t: Declare the byte arrays directly with alignas().
log_crypt(): Use memcpy_aligned instead of reinterpret_cast
on integers.
- Don't try to push down SELECTs that have a side effect
- In case the storage engine did support pushdown of SELECT with an INTO
clause, write the rows we've got from it into select->join->result,
and not thd->protocol. This way, SELECT ... INTO ... FROM
smart_engine_table will put the result into where instructed, and
NOT send it to the client.
Some fields were protected by log_sys.mutex, which adds quite some
overhead for readers. Some readers were submitting dirty reads.
log_t::lsn: Declare private and atomic. Add wrappers get_lsn()
and set_lsn() that will use relaxed memory access. Many accesses
to log_sys.lsn are still protected by log_sys.mutex; we avoid the
mutex for some readers.
log_t::flushed_to_disk_lsn: Declare private and atomic, and move
to the same cache line with log_t::lsn.
log_t::buf_free: Declare as size_t, and move to the same cache line
with log_t::lsn.
log_t::check_flush_or_checkpoint_: Declare private and atomic,
and move to the same cache line with log_t::lsn.
log_get_lsn(): Define as an alias of log_sys.get_lsn().
log_get_lsn_nowait(), log_peek_lsn(): Remove.
log_get_flush_lsn(): Define as an alias of log_sys.get_flush_lsn().
log_t::initiate_write(): Replaces log_buffer_sync_in_background().
O_DSYNC is faster than O_SYNC because it syncs as little as needed
(e.g. no timestamp changes)
This change is similar to change fsync() -> fdatasync() in MDEV-21382
The ut_crc32() function uses a hard-coded initial CRC-32C value of 0.
Replace it with ut_crc32_low(), which allows to specify the initial
checksum value, and provide an inlined compatibility wrapper ut_crc32().
Also, remove non-inlined wrapper functions on ARMv8 and POWER8,
and remove dead code (the generic implementation) on POWER8.
Note: The original AMD64 instruction set architecture in 2003 only
included SSE2. The CRC-32C instructions are part of the SSE4.2
instruction set extension for IA-32 and AMD64, with first processors
released in November 2007 (using the AMD Barcelona microarchitecture)
and November 2008 (Intel Nehalem microarchiteture). It might be safe
to assume that SSE4.2 is available on all currently used AMD64 based
systems, but we are not taking that step yet.
The configuration parameter innodb_scrub_log never really worked, as
reported in MDEV-13019 and MDEV-18370.
Because MDEV-14425 is changing the redo log format, the innodb_scrub_log
feature would have to be adjusted for it. Due to the known problems,
it is easier to remove the feature for now, and to ignore and deprecate
the parameters.
If old log contents should be kept secret, then enabling innodb_encrypt_log
or setting a smaller innodb_log_file_size could help.
MONITOR_PENDING_CHECKPOINT_WRITE and MONITOR_LOG_IO track
log_sys.n_pending_checkpoint_writes and log_sys.n_log_ios,
respectively. The MONITOR_INC calls are redundant, because
the values will be overwritten in srv_mon_process_existing_counter().
Compute MONITOR_LSN_CHECKPOINT_AGE on demand in
srv_mon_process_existing_counter().
This allows us to remove the overhead of MONITOR_SET
calls for the counter.
The function log_header_read() was only used during server startup,
and it will mostly be used only for reading checkpoint information
from pre-MDEV-14425 format redo log files.
Let us replace the function with more direct calls, so that
it is clearer what is going on. It is not strictly necessary to
hold any mutex during this operation, and because there will be
only a limited number of operations during early server startup,
it is not necessary to increment any I/O counters.
Simplify the logging of ALTER TABLE operations, by making use of the
TRX_UNDO_RENAME_TABLE undo log record that was introduced in
commit 0bc36758ba.
commit_try_rebuild(): Invoke row_rename_table_for_mysql() and
actually rename the files before committing the transaction.
fil_mtr_rename_log(), commit_cache_rebuild(),
log_append_on_checkpoint(), row_merge_rename_tables_dict(): Remove.
mtr_buf_copy_t, log_t::append_on_checkpoint: Remove.
row_rename_table_for_mysql(): If !use_fk, ignore missing foreign
keys. Remove a call to dict_table_rename_in_cache(), because
trx_rollback_to_savepoint() should invoke the function if needed.
In commit 138cbec5f2, we
computed an incorrect parameter to page_dir_split_slot(),
leading us to splitting the wrong directory slot, or
an out-of-bounds access when splitting the supremum slot.
This was once caught in the test innodb_gis.kill_server for
inserting records to a clustered index root page.
page_dir_split_slot(): Take the slot as a pointer, instead of
a numeric index.
page_apply_insert_redundant(), page_apply_insert_dynamic():
Rename slot to last_slot, and make owner_slot a pointer.
For undo log truncation, commit 055a3334ad
repurposed the MLOG_FILE_CREATE2 record with a nonzero page size
to indicate that an undo tablespace will be shrunk in size.
In commit 7ae21b18a6 the
MLOG_FILE_CREATE2 record was replaced by a FILE_CREATE record.
Now that the redo log encoding was changed, there is no actual need
to write a file name in the log record; it suffices to write the
page identifier of the first page that is not part of the file.
This TRIM_PAGES record could allow us to shrink any data files in the
future. For now, it will be limited to undo tablespaces.
mtr_t::log_file_op(): Remove the parameter first_page_no, because
it would always be 0 for file operations.
mtr_t::trim_pages(): Replaces fil_truncate_log().
mtr_t::log_write(): Avoid same_page encoding if !bpage&&!m_last.
fil_op_replay_rename(): Remove the constant parameter first_page_no=0.
This patch adds support of RENAME INDEX operation to the ALTER TABLE
statement. Code which determines if ALTER TABLE can be done in-place
for "simple" storage engines like MyISAM, Heap and etc. was updated to
handle ALTER TABLE ... RENAME INDEX as an in-place operation. Support
for in-place ALTER TABLE ... RENAME INDEX for InnoDB was covered by
MDEV-13301.
Syntax changes
==============
A new type of <alter_specification> is added:
<rename index clause> ::= RENAME ( INDEX | KEY ) <oldname> TO <newname>
Where <oldname> and <newname> are identifiers for old name and new
name of the index.
Semantic changes
================
The result of "ALTER TABLE t1 RENAME INDEX a TO b" is a table which
contents and structure are identical to the old version of 't1' with
the only exception index 'a' being called 'b'.
Neither <oldname> nor <newname> can be "primary". The index being
renamed should exist and its new name should not be occupied
by another index on the same table.
Related to: WL#6555, MDEV-13301
When connections go to same node and deadlock happens, BF abort should
not happen for victim thread. Fixed by guarding
`wsrep_handle_SR_rollback()` so that is called only for SR transactions.
Co-authored-by: Seppo Jaakola <seppo.jaakola@iki.fi>
Co-authored-by: Daniele Sciascia <daniele.sciascia@galeracluster.com>
Introduce special synchronization primitive group_commit_lock
for more efficient synchronization of redo log writing and flushing.
The goal is to reduce CPU consumption on log_write_up_to, to reduce
the spurious wakeups, and improve the throughput in write-intensive
benchmarks.
XA specification doesn't permit empty gtrid. It is now enforced by this
patch. This solution was agreed in favour of fixing InnoDB, which doesn't
expect empty XID since early 10.5.
Also fixed wrong assertion (and added a test cases) that didn't permit
64 bytes gtrid + 64 bytes bqual.
Inserting a record into an index page involves updating multiple
fields in the page header as well as updating the next-record links
and potentially updating fields related to the sparse page directory.
Let us cover the insert operations by higher-level log records, to avoid
'redundant' logging about the writes.
The code for applying the high-level log records will check the
consistency of the page thoroughly, to avoid crashes during recovery.
We will refuse to replay the inserts if any inconsistency is detected.
With innodb_force_recovery=1, recovery will continue, but the affected
pages may be more inconsistent if some changes were omitted.
mrec_ext_t: Introduce the EXTENDED record subtypes
INSERT_HEAP_REDUNDANT, INSERT_REUSE_REDUNDANT,
INSERT_HEAP_DYNAMIC, INSERT_REUSE_DYNAMIC.
The record will explicitly identify the page type and whether
the space will be allocated from PAGE_HEAP_TOP or reused from
the PAGE_FREE list. It will also tell how many bytes to copy
from the preceding record header and payload, and how to
initialize the rest of the record header and payload.
mtr_t::page_insert(): Write the high-level log records.
log_phys_t::apply(): Parse the high-level log records.
page_apply_insert_redundant(), page_apply_insert_dynamic():
Apply the high-level log records.
page_dir_split_slot(): Introduce a variant that does not write log
nor deal with ROW_FORMAT=COMPRESSED pages.
page_mem_alloc_heap(): Remove the mtr_t parameter
page_cur_insert_rec_low(): Write log only via mtr_t::page_insert().
This is a follow-up to commit 572d20757b
where we introduced the EXTENDED log record subtypes
DELETE_ROW_FORMAT_REDUNDANT and DELETE_ROW_FORMAT_DYNAMIC.
log_phys_t::apply(): If corruption was noticed, stop applying the log
unless innodb_force_recovery is set.
This is a follow-up to commit 84e3f9ce84
that introduced the EXTENDED log record of UNDO_APPEND subtype.
mtr_t::undo_append(): Accurately enforce the mtr_buf_t::MAX_DATA_SIZE
limit. Also, replace mtr_buf_t::push() with simpler code, to append 1 byte
to the log.
log_phys_t::undo_append(): Return whether the page was found to
be in an inconsistent state.
log_phys_t::apply(): If corruption was noticed, stop applying log
unless innodb_force_recovery is set.
This bug was introduced in
commit 7ae21b18a6
(the main commit of MDEV-12353).
page_cur_insert_rec_low(): Before entering the comparison loop, make sure
that the range does not exceed c_end already at the start of the loop.
The loop is only comparing for pointer equality, and that condition
cdm == c_end would never hold if the end was already exceeded in
the beginning. Also, skip the comparison altogether if we could find
at most 2 equal bytes.
PageBulk::insertPage(): Apply a similar change. It seems that this
code was correct, because the loop checks for cdm < c_end.
mrec_ext_t: Introduce DELETE_ROW_FORMAT_REDUNDANT,
DELETE_ROW_FORMAT_DYNAMIC.
mtr_t::page_delete(): Write DELETE_ROW_FORMAT_REDUNDANT or
DELETE_ROW_FORMAT_DYNAMIC log records. We log the byte offset
of the preceding record, so that on recovery we can easily
find everything to update. For DELETE_ROW_FORMAT_DYNAMIC,
we must also write the header and data size of the record.
We will retain the physical logging for ROW_FORMAT=COMPRESSED pages.
page_zip_dir_balance_slot(): Renamed from page_dir_balance_slot(),
and specialized for ROW_FORMAT=COMPRESSED only.
page_rec_set_n_owned(), page_dir_slot_set_n_owned(),
page_dir_balance_slot(): New variants that do not write any log.
page_mem_free(): Take data_size, extra_size as parameters.
Always zerofill the record payload.
page_cur_delete_rec(): For other than ROW_FORMAT=COMPRESSED,
only write log by mtr_t::page_delete().
There is no reason for the dummy index object dict_ind_redundant
to exist any more. It was only being passed to btr_create().
btr_create(): If !index, assume that a ROW_FORMAT=REDUNDANT
table is being created.
We could pass ibuf.index, dict_sys.sys_tables->indexes.start
and so on, if those objects had been initialized before the
function btr_create() is called.
recv_sys_t opened redo log files along with log_sys_t. That's why I
removed file sharing logic from InnoDB
in 9ef2d29ff4
But it was actually used to ensure that only one MariaDB instance
will touch the same InnoDB files.
os0file.cc: revert some changes done previously
mapped_file_t::map(): now has arguments read_only, nvme
file_io::open(): now has argument read_only
class file_os_io: make final
log_file_t::open(): now has argument read_only
We introduce an EXTENDED log record for appending an undo log record
to an undo log page. This is equivalent to the MLOG_UNDO_INSERT record
that was removed in commit f802c989ec,
only using more compact encoding.
mtr_t::log_write(): Fix a bug that affects longer log
record writes in the !same_page && !have_offset case.
Similar code is already implemented for the have_offset code path.
The bug was unobservable before we started to write longer
EXTENDED records. All !have_offset records (FREE_PAGE, INIT_PAGE,
EXTENDED) that were written so far are short, and we never write
RESERVED or OPTION records.
mtr_t::undo_append(): Write an UNDO_APPEND record.
log_phys_t::undo_append(): Apply an UNDO_APPEND record.
trx_undo_page_set_next_prev_and_add(),
trx_undo_page_report_modify(),
trx_undo_page_report_rename():
Invoke mtr_t::undo_append() instead of emitting WRITE records.
We introduce an EXTENDED log record for initializing an undo log page.
The size of the record will be 2 bytes plus the optional page identifier.
The entire undo page will be initialized, except the space that is
already reserved for TRX_UNDO_SEG_HDR in trx_undo_seg_create().
mtr_t::undo_create(): Write the UNDO_INIT record.
trx_undo_page_init(): Initialize the undo page corresponding to the
UNDO_INIT record. Unlike the former MLOG_UNDO_INIT record, we will
initialize almost the entire page, including initializing the
TRX_UNDO_PAGE_NODE to an empty list node, so that the subsequent call
to flst_init() will avoid writing log for the undo page.
Now there can be only one log file instead of several which
logically work as a single file.
Possible names of redo log files: ib_logfile0,
ib_logfile101 (for just created one)
innodb_log_fiels_in_group: value of this variable is not used
by InnoDB. Possible values are still 1..100, to not break upgrade
LOG_FILE_NAME: add constant of value "ib_logfile0"
LOG_FILE_NAME_PREFIX: add constant of value "ib_logfile"
get_log_file_path(): convenience function that returns full
path of a redo log file
SRV_N_LOG_FILES_MAX: removed
srv_n_log_files: we can't remove this for compatibility reasons,
but now server doesn't use this variable
log_sys_t::file::fd: now just one, not std::vector
log_sys_t::log_capacity: removed word 'group'
find_and_check_log_file(): part of logic from huge srv_start()
moved here
recv_sys_t::files: file descriptors of redo log files.
There can be several of those in case we're upgrading
from older MariaDB version.
recv_sys_t::remove_extra_log_files: whether to remove
ib_logfile{1,2,3...} after successfull upgrade.
recv_sys_t::read(): open if needed and read from one
of several log files
recv_sys_t::files_size(): open if needed and return files count
redo_file_sizes_are_correct(): check that redo log files
sizes are equal. Just to log an error for a user.
Corresponding check was moved from srv0start.cc
namespace deprecated: put all deprecated variables here to
prevent usage of it by us, developers
Do not rebuild index when it's key part converted from utf8mb3 to utf8mb4
but key part stays the same.
dict_index_add_to_cache(): assert that prefix_len is divided by mbmaxlen
ha_innobase::compare_key_parts(): compare key part lenght in symbols instead
of bytes.
We plan use the redo log record main type code 0x20 for
InnoDB specific index page operations.
mrec_type_t: Rename INIT_INDEX_PAGE to EXTENDED.
mrec_ext_t: The EXTENDED subtypes.
This is a non-functional change: the redo log record encoding
that was introduced in commit 7ae21b18a6
is not affected.
btr_page_reorganize_low(): Log only the changed data in the page.
TODO: Do not copy the entire changed payload to the redo log.
Emit a combination of MEMMOVE and WRITE records to reduce the log volume.
commit 08ba388713 of MDEV-12353
introduced an incorrect assumption, which was documented by
the failing assertion.
After instant ADD COLUMN, we can have a null (and in-place) UPDATE
of NULL to NULL. No data needs to be written for such updates.
For ROW_FORMAT=REDUNDANT, we reserve space for the NULL values,
and to be compatible with existing behaviour, we will zerofill
the unused data bytes when updating to NULL value.
trx_purge_free_segment(): In some cases (observed when running
the test innodb_zip.wl5522_debug_zip), there is no change to
the TRX_UNDO_NEEDS_PURGE field. Add mtr_t::OPT to disable a debug check.
The bogus debug check was introduced in
commit 56f6dab1d0.
We add FIXME comments and some sketch code for the following cases:
It is possible to write considerably less log for ROW_FORMAT=COMPRESSED
pages. For now, we will delete the records one by one.
It is also possible to treat 'deleting the last records' as a special
case that would involve shrinking PAGE_HEAP_TOP. That should reduce
the need of reorganizing pages.
page_mem_free(): When deleting the very last record of the page,
even if the record did not fully utilize all bytes in a
former PAGE_FREE record, truncate the PAGE_HEAP_TOP and reduce
PAGE_GARBAGE by the saved amount.
fsp_page_create(): Always initialize the page. The logic to
avoid initialization was made redundant and should have been removed
in mysql/mysql-server@ce0a1e85e2
(MySQL 5.7.5).
btr_store_big_rec_extern_fields(): Remove the redundant initialization
of FIL_PAGE_PREV and FIL_PAGE_NEXT. An INIT_PAGE record will have
been written already. Only write the ROW_FORMAT=COMPRESSED page payload
from FIL_PAGE_DATA onwards. We were unnecessarily writing from
FIL_PAGE_TYPE onwards, which caused an assertion failure on recovery:
recv_sys_t::alloc(size_t): Assertion 'len <= srv_page_size' failed
when running the following tests:
./mtr --no-reorder innodb_zip.blob,4k innodb_zip.bug56680,4k
trx_rseg_write_wsrep_checkpoint(): Add missing mtr_t::OPT,
and avoid an unnecessary call to mtr_t::memset().
This addresses a debug assertion failure in wsrep_info.plugin.
page_update_max_trx_id(), page_delete_rec_list_end(): Remove conditions
on recv_recovery_is_on(). These conditions should have been removed in
or before commit f8a9f90667
(removing the support for crash-upgrade).
The physical redo log based recovery will not call such high-level code.
page_mem_free(): When deleting the last record of a page,
do not add it to the PAGE_FREE list, but instead truncate the
PAGE_HEAP_TOP. Modify the page header fields by writing fewer
records.
page_cur_delete_rec(): Let page_mem_free() reset the PAGE_LAST_INSERT.
page_header_reset_last_insert(): Issue memset(), not memcpy(), for
the ROW_FORMAT=COMPRESSED page.
Optionally use libpmem for InnoDB redo log writing.
When server is built -DWITH_PMEM=ON InnoDB tries to detect
that redo log is located on persistent memory storage and
uses faster file access method.
When server is built with -DWITH_PMEM=OFF preprocessor is
used to ensure that no slowdown will present due to allocations
and virtual function calls. So, we don't slow down server
in a common case.
mapped_file_t: an map file, unmap file and returns mapped memory buffer
file_io: abstraction around memory mapped files and file descriptors.
Allows writing, reading and flushing to files.
file_io::writes_are_durable(): notable method of a class.
When it returns true writes are flushed immediately.
file_os_io: file descriptor based file access. Depends on a global state
like srv_read_only_mode
file_pmem_io: file access via libpmem
This is a collaboration work with Sergey Vojtovich
This is a fixup for commit 7ae21b18a6.
It turns out that even if we in the future made LSN
count mini-transactions instead of bytes, we will need
both start LSN and end LSN, which must exactly match
between mtr_t::commit() and log_phys_t::apply().
log_rec_t::lsn: Restore the const qualifier.
log_phys_t::append(): Remove the lsn parameter. Both the start
and end LSN must remain unchanged. We can only append log from
the same mini-transaction to a single log record snippet.
If we combined the log from mini-transactions A and B, it could
happen that the FIL_PAGE_LSN of the page is somewhere between
A.start_lsn and B.start_lsn. In that case, also the log of B
would be wrongly skipped.
recv_sys_t::add(): Assert that if the start LSN matches, also
the end LSN will match.
log_t::FORMAT_10_5: physical redo log format tag
log_phys_t: Buffered records in the physical format.
The log record bytes will follow the last data field,
making use of alignment padding that would otherwise be wasted.
If there are multiple records for the same page, also those
may be appended to an existing log_phys_t object if the memory
is available.
In the physical format, the first byte of a record identifies the
record and its length (up to 15 bytes). For longer records, the
immediately following bytes will encode the remaining length
in a variable-length encoding. Usually, a variable-length-encoded
page identifier will follow, followed by optional payload, whose
length is included in the initially encoded total record length.
When a mini-transaction is updating multiple fields in a page,
it can avoid repeating the tablespace identifier and page number
by setting the same_page flag (most significant bit) in the first
byte of the log record. The byte offset of the record will be
relative to where the previous record for that page ended.
Until MDEV-14425 introduces a separate file-level log for
redo log checkpoints and file operations, we will write the
file-level records in the page-level redo log file.
The record FILE_CHECKPOINT (which replaces MLOG_CHECKPOINT)
will be removed in MDEV-14425, and one sequential scan of the
page recovery log will suffice.
Compared to MLOG_FILE_CREATE2, FILE_CREATE will not include any flags.
If the information is needed, it can be parsed from WRITE records that
modify FSP_SPACE_FLAGS.
MLOG_ZIP_WRITE_STRING: Remove. The record was only introduced temporarily
as part of this work, before being replaced with WRITE (along with
MLOG_WRITE_STRING, MLOG_1BYTE, MLOG_nBYTES).
mtr_buf_t::empty(): Check if the buffer is empty.
mtr_t::m_n_log_recs: Remove. It suffices to check if m_log is empty.
mtr_t::m_last, mtr_t::m_last_offset: End of the latest m_log record,
for the same_page encoding.
page_recv_t::last_offset: Reflects mtr_t::m_last_offset.
Valid values for last_offset during recovery should be 0 or above 8.
(The first 8 bytes of a page are the checksum and the page number,
and neither are ever updated directly by log records.)
Internally, the special value 1 indicates that the same_page form
will not be allowed for the subsequent record.
mtr_t::page_create(): Take the block descriptor as parameter,
so that it can be compared to mtr_t::m_last. The INIT_INDEX_PAGE
record will always followed by a subtype byte, because same_page
records must be longer than 1 byte.
trx_undo_page_init(): Combine the writes in WRITE record.
trx_undo_header_create(): Write 4 bytes using a special MEMSET
record that includes 1 bytes of length and 2 bytes of payload.
flst_write_addr(): Define as a static function. Combine the writes.
flst_zero_both(): Replaces two flst_zero_addr() calls.
flst_init(): Do not inline the function.
fsp_free_seg_inode(): Zerofill the whole inode.
fsp_apply_init_file_page(): Initialize FIL_PAGE_PREV,FIL_PAGE_NEXT
to FIL_NULL when using the physical format.
btr_create(): Assert !page_has_siblings() because fsp_apply_init_file_page()
must have been invoked.
fil_ibd_create(): Do not write FILE_MODIFY after FILE_CREATE.
fil_names_dirty_and_write(): Remove the parameter mtr.
Write the records using a separate mini-transaction object,
because any FILE_ records must be at the start of a mini-transaction log.
recv_recover_page(): Add a fil_space_t* parameter.
After applying log to the a ROW_FORMAT=COMPRESSED page,
invoke buf_zip_decompress() to restore the uncompressed page.
buf_page_io_complete(): Remove the temporary hack to discard the
uncompressed page of a ROW_FORMAT=COMPRESSED page.
page_zip_write_header(): Remove. Use mtr_t::write() or
mtr_t::memset() instead, and update the compressed page frame
separately.
trx_undo_header_add_space_for_xid(): Remove.
trx_undo_seg_create(): Perform the changes that were previously
made by trx_undo_header_add_space_for_xid().
btr_reset_instant(): New function: Reset the table to MariaDB 10.2
or 10.3 format when rolling back an instant ALTER TABLE operation.
page_rec_find_owner_rec(): Merge with the only callers.
page_cur_insert_rec_low(): Combine writes by using a local buffer.
MEMMOVE data from the preceding record whenever feasible
(copying at least 3 bytes).
page_cur_insert_rec_zip(): Combine writes to page header fields.
PageBulk::insertPage(): Issue MEMMOVE records to copy a matching
part from the preceding record.
PageBulk::finishPage(): Combine the writes to the page header
and to the sparse page directory slots.
mtr_t::write(): Only log the least significant (last) bytes
of multi-byte fields that actually differ.
For updating FSP_SIZE, we must always write all 4 bytes to the
redo log, so that the fil_space_set_recv_size() logic in
recv_sys_t::parse() will work.
mtr_t::memcpy(), mtr_t::zmemcpy(): Take a pointer argument
instead of a numeric offset to the page frame. Only log the
last bytes of multi-byte fields that actually differ.
In fil_space_crypt_t::write_page0(), we must log also any
unchanged bytes, so that recovery will recognize the record
and invoke fil_crypt_parse().
Future work:
MDEV-21724 Optimize page_cur_insert_rec_low() redo logging
MDEV-21725 Optimize btr_page_reorganize_low() redo logging
MDEV-21727 Optimize redo logging for ROW_FORMAT=COMPRESSED
NOTE: This may break crash-upgrade from a dataset that was
created with innodb_log_optimize_ddl=ON. Also due to
ROW_FORMAT=COMPRESSED pages, it will be easiest to disallow
crash-upgrade.
It would be more robust to disable the MDEV-12699 logic when
crash-upgrading from old redo log format.
log_optimized_ddl_op: Remove.
fil_space_t::enable_lsn, file_name_t::enable_lsn: Remove.
ddl_tracker_t::optimized_ddl: Remove.
TODO: Remove ddl_tracker
mtr_t::log_write_low(): Replaces mlog_write_initial_log_record_low().
mtr_t::log_file_op(): Replaces fil_op_write_log().
mtr_t::free(): Write MLOG_INIT_FREE_PAGE.
mtr_t::init(): Write MLOG_INIT_FILE_PAGE2.
mtr_t::page_create(): Write record about the partial initialization
of an index page.
mlog_catenate_ulint(), mlog_catenate_string(),
mlog_open(), mlog_close(): Remove.
Pass buf_block_t* to all functions that write redo log.
Specifically, replace the parameters page,page_zip
with buf_block_t* block in page_zip_ functions.
page_mem_alloc_free(), page_dir_set_n_heap(), page_ptr_set_direction():
Merge with the callers.
page_direction_reset(), page_direction_increment(),
page_zip_dir_insert(), page_zip_write_rec_ext(), page_zip_write_rec():
Add the parameter mtr, and write log.
PageBulk::insert(), PageBulk::finish(): Write log for all changes.
page_cur_rec_insert(), page_cur_insert_rec_write_log(),
page_cur_insert_rec_write_log(): Remove.
page_rec_set_next(), page_header_set_field(), page_header_set_ptr():
Remove. Use lower-level operations with or without logging.
page_zip_dir_add_slot(): Move to the same compilation unit with
its only caller, page_cur_insert_rec_zip().
page_cur_insert_rec_zip(): Mark pieces of code that must be skipped
once this task is completed.
btr_defragment_chunk(): Before starting a mini-transaction that
is writing (a lot), invoke log_free_check(). This should allow
the test innodb.innodb_defrag_concurrent to pass with the
mtr default_mysqld.cnf setting of innodb_log_file_size=10M.
MLOG_BUF_MARGIN: Remove.
page_zip_compress_write_log(): Write MLOG_INIT_FILE_PAGE2
and MLOG_ZIP_WRITE_STRING records instead of MLOG_ZIP_PAGE_COMPRESS.
This depends on the changes to buf_page_io_complete() and friends
in the parent commit.
No longer write the following redo log records:
MLOG_COMP_LIST_END_DELETE, MLOG_LIST_END_DELETE,
MLOG_COMP_LIST_START_DELETE, MLOG_LIST_START_DELETE,
MLOG_REC_DELETE,MLOG_COMP_REC_DELETE.
Each individual deleted record will be logged separately
using physical log records.
page_dir_slot_set_n_owned(),
page_zip_rec_set_owned(), page_zip_dir_delete(), page_zip_clear_rec():
Add the parameter mtr, and write redo log.
page_dir_slot_set_rec(): Remove. Replaced with lower-level operations
that write redo log when necessary.
page_rec_set_n_owned(): Replaces rec_set_n_owned_old(),
rec_set_n_owned_new().
rec_set_heap_no(): Replaces rec_set_heap_no_old(), rec_set_heap_no_new().
page_mem_free(), page_dir_split_slot(), page_dir_balance_slot():
Add the parameter mtr.
page_dir_set_n_slots(): Merge with the caller page_dir_split_slot().
page_dir_slot_set_rec(): Merge with the callers page_dir_split_slot()
and page_dir_balance_slot().
page_cur_insert_rec_low(), page_cur_insert_rec_zip():
Suppress the logging of lower-level operations.
page_cur_delete_rec_write_log(): Remove.
page_cur_delete_rec(): Do not tolerate mtr=NULL.
rec_convert_dtuple_to_rec_old(), rec_convert_dtuple_to_rec_comp():
Replace rec_set_heap_no_old() and rec_set_heap_no_new() with direct
access that does not involve redo logging.
mtr_t::memcpy(): Do allow non-redo-logged writes to uncompressed pages
of ROW_FORMAT=COMPRESSED pages.
buf_page_io_complete(): Evict the uncompressed page of
a ROW_FORMAT=COMPRESSED page after recovery. Because we no longer
write logical log records for deleting index records, but instead
write physical records that may refer directly to the compressed
page frame of a ROW_FORMAT=COMPRESSED page, and because on recovery
we will only apply the changes to the ROW_FORMAT=COMPRESSED page,
the uncompressed page frame can be stale until page_zip_decompress()
is executed.
recv_parse_or_apply_log_rec_body(): After applying MLOG_ZIP_WRITE_STRING,
ensure that the FIL_PAGE_TYPE of the uncompressed page matches the
compressed page, because buf_flush_init_for_writing() assumes that
field to be valid.
mlog_init_t::mark_ibuf_exist(): Invoke page_zip_decompress(), because
the uncompressed page after buf_page_create() is not necessarily
up to date.
buf_LRU_block_remove_hashed(): Bypass a page_zip_validate() check
during redo log apply.
recv_apply_hashed_log_recs(): Invoke mlog_init.mark_ibuf_exist()
also for the last batch, to ensure that page_zip_decompress() will
be called for freshly initialized pages.
page_create(): Create normal B-tree pages. Callers that create
R-tree pages will set FIL_PAGE_TYPE and reset the split
sequence number afterwards.
The creation of ROW_FORMAT=COMPRESSED pages is unaffected;
they will be logged as compressed page images.
page_create_low(): Take const buf_block_t* as a parameter.
Let the callers invoke buf_block_modify_clock_inc().
btr_cur_upd_rec_sys(): Replaces row_upd_rec_sys_fields() and
implements redo logging.
row_upd_rec_sys_fields_in_recovery(): Remove, and merge to the
only remaining caller btr_cur_parse_update_in_place().
btr_cur_del_mark_set_clust_rec_log(),
btr_cur_del_mark_set_sec_rec_log(),
btr_cur_set_deleted_flag_for_ibuf():
Remove, and replace with btr_rec_set_deleted<bool>().
page_zip_rec_set_deleted(): Add the parameter mtr, and write a
MLOG_ZIP_WRITE_STRING record to the log.
Log the low-level operations for ROW_FORMAT=COMPRESSED index pages
using a new record, MLOG_ZIP_WRITE_STRING. We will still use
MLOG_1BYTE,..., MLOG_8BYTES or MLOG_WRITE_STRING for operations
on other than index pages (such as the page allocation bitmap pages).
We will stop writing the record MLOG_ZIP_PAGE_COMPRESS later, after
replacing all MLOG_REC_ and MLOG_COMP_REC_ that update index pages.
Log page reorganize as a series of insert operations.
This will make the redo log volume proportional to the page payload size.
btr_page_reorganize_low(): Add template <bool recovery=false>
btr_page_reorganize_block(): Remove the parameter 'bool recovery'
Instead of writing the high-level redo log records
MLOG_LIST_END_COPY_CREATED, MLOG_COMP_LIST_END_COPY_CREATED
write log for each individual insert of a record.
page_copy_rec_list_end_to_created_page(): Remove.
This will improve the fill factor of some pages.
Adjust some tests accordingly.
PageBulk::init(), PageBulk::finish(): Avoid setting bogus limits
to PAGE_HEAP_TOP and PAGE_N_DIR_SLOTS. Avoid accessor functions
that would enforce these limits before the correct ones are set
at the end of PageBulk::finish().
page_zip_reorganize(): Restore the page on failure.
In callers, omit now-redundant calls to page_zip_decompress().
btr_page_reorganize_low(): Define in static scope only, and
remove the z_level parameter. Assert that ROW_FORMAT is not COMPRESSED.
btr_page_reorganize_block(), btr_page_reorganize(): Invoke
page_zip_reorganize() for ROW_FORMAT=COMPRESSED.
page_zip_compress_write_log_no_data(): Remove.
We no longer write the MLOG_ZIP_PAGE_COMPRESS_NO_DATA record.
Instead, we will write MLOG_ZIP_PAGE_COMPRESS records.
For compatibility with diagnostic software, let us
return a dummy buffer pool identifier 0 and restore
the columns that were initially deleted in
commit 1a6f708ec5:
information_schema.innodb_buffer_page.pool_id
information_schema.innodb_buffer_page_lru.pool_id
information_schema.innodb_buffer_pool_stats.pool_id
information_schema.innodb_cmpmem.buffer_pool_instance
information_schema.innodb_cmpmem_reset.buffer_pool_instance
Thanks to Vladislav Vaintroub for pointing this out.
Our benchmarking efforts indicate that the reasons for splitting the
buf_pool in commit c18084f71b
have mostly gone away, possibly as a result of
mysql/mysql-server@ce6109ebfd
or similar work.
Only in one write-heavy benchmark where the working set size is
ten times the buffer pool size, the buf_pool->mutex would be
less contended with 4 buffer pool instances than with 1 instance,
in buf_page_io_complete(). That contention could be alleviated
further by making more use of std::atomic and by splitting
buf_pool_t::mutex further (MDEV-15053).
We will deprecate and ignore the following parameters:
innodb_buffer_pool_instances
innodb_page_cleaners
There will be only one buffer pool and one page cleaner task.
In a number of INFORMATION_SCHEMA views, columns that indicated
the buffer pool instance will be removed:
information_schema.innodb_buffer_page.pool_id
information_schema.innodb_buffer_page_lru.pool_id
information_schema.innodb_buffer_pool_stats.pool_id
information_schema.innodb_cmpmem.buffer_pool_instance
information_schema.innodb_cmpmem_reset.buffer_pool_instance
During native table rebuild or index creation, InnoDB used to skip
redo logging and write MLOG_INDEX_LOAD records to inform crash recovery
and Mariabackup of the gaps in redo log. This is fragile and prohibits
some optimizations, such as skipping the doublewrite buffer for
newly (re)initialized pages (MDEV-19738).
row_merge_write_redo(): Remove. We do not write MLOG_INDEX_LOAD
records any more. Instead, we write full redo log.
FlushObserver: Remove.
fseg_free_page_func(): Remove the parameter log. Redo logging
cannot be disabled.
fil_space_t::redo_skipped_count: Remove.
We cannot remove buf_block_t::skip_flush_check, because PageBulk
will temporarily generate invalid B-tree pages in the buffer pool.
Let us define page_id_t as a thin wrapper of uint64_t so that
the comparison operators can be simplified. This is a follow-up
to the original commit 14be814380.
The comparison operator for recv_sys.pages.emplace() turned out to be
a busy spot in a recovery benchmark. That data structure was introduced
in MDEV-19586 in commit 177a571e01.
