Remove the bug-compatible crc32 algorithm variant that was added
to allow an upgrade from data files from big-endian systems where
innodb_checksum_algorithm=crc32 was used on MySQL 5.6
or MariaDB 10.0 or 10.1.
Affected users should be able to recompute page checksums using
innochecksum.
In MySQL 5.7, it was noticed that files are not portable between
big-endian and little-endian processor architectures
(such as SPARC and x86), because the original implementation of
innodb_checksum_algorithm=crc32 was not byte order agnostic.
A byte order agnostic implementation of innodb_checksum_algorithm=crc32
was only added to MySQL 5.7, not backported to 5.6. Consequently,
MariaDB Server versions 10.0 and 10.1 only contain the CRC-32C
implementation that works incorrectly on big-endian architectures,
and MariaDB Server 10.2.2 got the byte-order agnostic CRC-32C
implementation from MySQL 5.7.
MySQL 5.7 introduced a "legacy crc32" variant that is functionally
equivalent to the big-endian version of the original crc32 implementation.
Thanks to this variant, old data files can be transferred from big-endian
systems to newer versions.
Introducing new variants of checksum algorithms (without introducing
new names for them, or something on the pages themselves to identify
the algorithm) generally is a bad idea, because each checksum algorithm
is like a lottery ticket. The more algorithms you try, the more likely
it will be for the checksum to match on a corrupted page.
So, essentially MySQL 5.7 weakened innodb_checksum_algorithm=crc32,
and MariaDB 10.2.2 inherited this weakening.
We introduce a build option that together with MDEV-17957
makes innodb_checksum_algorithm=strict_crc32 strict again
by only allowing one variant of the checksum to match.
WITH_INNODB_BUG_ENDIAN_CRC32: A new cmake option for enabling the
bug-compatible "legacy crc32" checksum. This is only enabled on
big-endian systems by default, to facilitate an upgrade from
MariaDB 10.0 or 10.1. Checked by #ifdef INNODB_BUG_ENDIAN_CRC32.
ut_crc32_byte_by_byte: Remove (unused function).
legacy_big_endian_checksum: Remove. This variable seems to have
unnecessarily complicated the logic. When the weakening is enabled,
we must always fall back to the buggy checksum.
buf_page_check_crc32(): A helper function to compute one or
two CRC-32C variants.
Also, related to MDEV-15522, MDEV-17304, MDEV-17835,
remove the Galera xtrabackup tests, because xtrabackup never worked
with MariaDB Server 10.3 due to InnoDB redo log format changes.
Stop supporting the additional *trunc.log files that were
introduced via MySQL 5.7 to MariaDB Server 10.2 and 10.3.
DB_TABLESPACE_TRUNCATED: Remove.
purge_sys.truncate: A new structure to track undo tablespace
file truncation.
srv_start(): Remove the call to buf_pool_invalidate(). It is
no longer necessary, given that we no longer access things in
ways that violate the ARIES protocol. This call was originally
added for innodb_file_format, and it may later have been necessary
for the proper function of the MySQL 5.7 TRUNCATE recovery, which
we are now removing.
trx_purge_cleanse_purge_queue(): Take the undo tablespace as a
parameter.
trx_purge_truncate_history(): Rewrite everything mostly in a
single function, replacing references to undo::Truncate.
recv_apply_hashed_log_recs(): If any redo log is to be applied,
and if the log_sys.log.subformat indicates that separately
logged truncate may have been used, refuse to proceed except if
innodb_force_recovery is set. We will still refuse crash-upgrade
if TRUNCATE TABLE was logged. Undo tablespace truncation would
only be logged in undo*trunc.log files, which we are no longer
checking for.
Remove unused InnoDB function parameters and functions.
i_s_sys_virtual_fill_table(): Do not allocate heap memory.
mtr_is_block_fix(): Replace with mtr_memo_contains().
mtr_is_page_fix(): Replace with mtr_memo_contains_page().
Take snapshot of registered read-write transaction identifiers directly
from rw_trx_hash. It immediately saves one trx_sys.mutex lock, reduces
size of another critical section protected by this mutex, and makes
further optimisations like removing trx_sys_t::serialisation_list
possible.
Downside of this approach is bigger overhead for view opening, because
iterating LF_HASH is more expensive compared to taking snapshot of an
array. However for low concurrency overhead difference is negligible,
while for high concurrency mutex is much bigger evil.
Currently we still take trx_sys.mutex to serialise ReadView creation.
This is required to keep serialisation_list ordered by trx->no as well
as not to let purge thread to create more recent snapshot while another
thread gets suspended during creation of older snapshot. This will
become completely mutex free along with serialisation_list removal.
Compared to previous implementation removing element from rw_trx_hash
and serialisation_list is not atomic. We disregard all possible bad
consequences (if there're any) since it will be solved along with
serialisation_list removal.
Big endian checksum is needed to workaround 10+ years old bug, where checksum
was calculated incorrectly on big endian hardware. We can still checksum such
tablespaces using software implementation of CRC32.
Replace all references in InnoDB and XtraDB error log messages
to bugs.mysql.com with references to https://jira.mariadb.org/.
The original merge
commit 4274d0bf57
was accidentally reverted by the subsequent merge
commit 3b35d745c3
