and
MDEV-23414 Assertion `res->charset() == item->collation.collation' failed in Type_handler_string_result::make_packed_sort_key_part
pack_sort_string() *must* take a collation from the Item, not from the
String value. Because when casting a string to _binary the original
String is not copied for performance reasons, it's reused but its
collation does not match Item's collation anymore.
Note, that String's collation cannot be simply changed to _binary,
because for an Item_string literal the original String must stay
unchanged for the duration of the query.
this partially reverts 61c15ebe32
An unfortunate performance regression was introduced in
commit b1ab211dee (MDEV-15053)
that affects workloads where the working set is larger than
the buffer pool.
We used to terminate the loop in buf_LRU_scan_and_free_block()
when we succeeded to free a replaceable buffer pool block.
Due to the regression, we would keep freeing all replaceable
blocks until we reach the end of the list or encounter a block
that had never been accessed because it had been brought in
by read-ahead.
for the functionality that was part of the server for years
and is moved in 10.5 into a [statically linked] plugin
without changing the underlying code.
this makes it a weak dependency, signalling that ColumnStore can work
without jemalloc and that while jemalloc is desired, missing jemalloc
is not a fatal error.
depending on build config the error might be hidded,
in particular liblz4.so and libjemalloc.so make it to disappear,
but with -DWITH_INNODB_LZ4=NO -DWITH_JEMALLOC=NO it reappears.
Final added to:
- All reasonable classes inhereted from Field
- All classes inhereted from Protocol
- Almost all Handler classes
- Some important Item classes
The stripped size of mariadbd is just 4K smaller, but several object files
showed notable improvements in common execution paths.
- Checked field.o and item_sum.o
Other things:
- Added 'override' to a few class functions touched by this patch.
- Removed 'virtual' from a new class functions that had/got 'override'
- Changed Protocol_discard to inherit from Protocol instad of Protocol_text
In commit fd9ca2a742 (MDEV-23295)
we added a debug assertion, which caught a similar bug.
prepare_inplace_alter_table_dict(): If we had promised that
ALGORITHM=INPLACE or ALGORITHM=NOCOPY is supported, we must
preserve the ROW_FORMAT.
Problem:- rpl_parallel2 was failing non-deterministically
Analysis:-
When FLUSH TABLES WITH READ LOCK is executed, it will allow all worker
threads to complete their ongoing transactions and then it will pause them.
At this state FTWRL will proceed to acquire global read lock. FTWRL first
blocks threads from starting new commits, then upgrades the lock to block
commit of existing transactions.
Step1:
FLUSH TABLES WITH READ LOCK - Blocks new commits
Step2:
* STOP SLAVE command enables 'force_abort=1' which unblocks workers,
they continue to execute events.
* T1: Waits in 'record_gtid' call to update 'gtid_slave_pos' table with
its current GTID, but it is blocked becuase of Step1.
* T2: Holds COMMIT lock and waits for T1 to commit.
Step3:
FLUSH TABLES WITH READ LOCK - Waiting to get BLOCK_COMMIT.
This results in deadlock. When STOP SLAVE command allows paused workers to
proceed, workers should skip the execution of all further events, similar
to 'conservative' parallel mode.
Solution:-
We will assign 1 to skip_event_group when we are aborted in do_ftwrl_wait.
rpl_parallel_entry->pause_sub_id is only reset when force_abort is off in
rpl_pause_after_ftwrl.
The parameters innodb_thread_concurrency and innodb_commit_concurrency
were useful years ago when both computing resources and the implementation
of some shared data structures were limited. MySQL 5.0 or 5.1 had trouble
scaling beyond 8 concurrent connections. Most of the scalability bottlenecks
have been removed since then, and the transactions per second delivered
by MariaDB Server 10.5 should not dramatically drop upon exceeding the
'optimal' number of connections.
Hence, enabling any concurrency throttling for InnoDB actually makes
things worse. We have seen many customers mistakenly setting this to a
small value like 16 or 64 and then complaining the server was slow.
Ignoring the parameters allows us to remove some normally unused code
and data structures, which could slightly improve performance.
innodb_thread_concurrency, innodb_commit_concurrency,
innodb_replication_delay, innodb_concurrency_tickets,
innodb_thread_sleep_delay, innodb_adaptive_max_sleep_delay:
Deprecate and ignore; hard-wire to 0.
The column INFORMATION_SCHEMA.INNODB_TRX.trx_concurrency_tickets
will always report 0.
Problem:- rpl_parallel2 was failing non-deterministically
Analysis:-
When FLUSH TABLES WITH READ LOCK is executed, it will allow all worker
threads to complete their ongoing transactions and then it will pause them.
At this state FTWRL will proceed to acquire global read lock. FTWRL first
blocks threads from starting new commits, then upgrades the lock to block
commit of existing transactions.
Step1:
FLUSH TABLES WITH READ LOCK - Blocks new commits
Step2:
* STOP SLAVE command enables 'force_abort=1' which unblocks workers,
they continue to execute events.
* T1: Waits in 'record_gtid' call to update 'gtid_slave_pos' table with
its current GTID, but it is blocked becuase of Step1.
* T2: Holds COMMIT lock and waits for T1 to commit.
Step3:
FLUSH TABLES WITH READ LOCK - Waiting to get BLOCK_COMMIT.
This results in deadlock. When STOP SLAVE command allows paused workers to
proceed, workers should skip the execution of all further events, similar
to 'conservative' parallel mode.
Solution:-
We will assign 1 to skip_event_group when we are aborted in do_ftwrl_wait.
rpl_parallel_entry->pause_sub_id is only reset when force_abort is off in
rpl_pause_after_ftwrl.
/home/buildbot/buildbot/build/storage/xtradb/mtr/mtr0mtr.cc:97:37: error: invalid access to non-static data member ‘fil_space_t::latch’ of NULL object [-Werror=invalid-offsetof]
Changing that in case of *INT and hex hybrid input:
- ROUND(x,NULL) creates a column with the same type as x.
The old code created a DOUBLE column, which was not relevant at all.
This change simplifies the code a lot.
- ROUND(x,non_constant) creates a column of the INT, BIGINT or DECIMAL
data type (depending on the exact type of x).
The old code created a column of the DOUBLE data type,
which lead to precision loss. Hence MDEV-23366.
- ROUND(bigint_30,negative_constant) creates a column of the DECIMAL(30,0)
data type. The old code created DECIMAL(29,0), which looked strange:
the data type promoted to a higher one, but max length reduced.
Now the length attribute is preserved.
failed or late ER_PERIOD_FIELD_WRONG_ATTRIBUTES upon attempt to create
existing table
Analysis: Error state is not stored when field is checked in
Table_period_info::check_field()
Fix: Store error state by setting res to true.
Item_func_round::fix_arg_int() did not take into account cases
when the result of ROUND(bigint_subject,negative_precision)
could go outside of the BIGINT range. The old code only incremented
max_length, but did not extend change the data type.
Fixing to extend the data type (together with max_length increment).
MDEV-22871 refactored the InnoDB buf_pool.page_hash to use a simple
rw-lock implementation that avoids a spinloop between non-contended
read-lock requests, simply using std::atomic::fetch_add() for the
lock acquisition.
Alas, in a write-heavy stress test on a 56-core system with 1,000
concurrent client connections, the server would stop processing
any transactions every now and then. The reason turned out to be
false sharing. Attaching a debugger to the server during one such
hang revealed that 22 of the 1,033 threads were polling in
page_hash_latch::read_lock_wait() on the same object, which appeared
to be in unlocked state (no readers or writers). All 22 requests were
for accessing an undo log page, with a distinct page number.
To eliminate such false sharing, we will make buf_pool.page_hash.array
contain one page_hash_latch per CPU data cache line. On AMD64, this
will pad the size of the array by 8/7, or almost 15%. For a 50GiB
buffer pool of 16KiB pages, the buf_pool.page_hash.array would
grow from 25MiB to 28.6MiB. On other instruction set architectures,
the incurred memory overhead may be smaller.
Thanks to Vladislav Vaintroub for noticing this anomaly.
The condition in Item_func_round::fix_arg_int() to decide whether:
- we can preserve the data type of args[0] versus
- the result can go outside of the args[0] data type
was wrong.
The data type of the first argument can be preserved in these cases:
- TRUNCATE(x, n)
- ROUND(x, n>=0)
Fixing the condition accordingly.
