optimizer-adjust_secondary_key_costs is added to provide 2 small
adjustments to the 10.x optimizer cost model. This can be used in the
case where the optimizer wrongly uses a secondary key instead of a
clustered primary key.
The reason behind this change is that MariaDB 10.x does not take into
account that for engines like InnoDB, that scanning a primary key can be
up to 7x faster than scanning a secondary key + read the row data trough
the primary key.
The different values for optimizer_adjust_secondary_key_costs are:
optimizer_adjust_secondary_key_costs=0
- No changes to current model
optimizer_adjust_secondary_key_costs=1
- Ensure that the cost of of secondary indexes has a cost of at
least 5x times the cost of a clustered primary key (if one exists).
This disables part of the worst_seek optimization described below.
optimizer_adjust_secondary_key_costs=2
- Disable "worst_seek optimization" and adjust filter cost slightly
(add cost of 1 if filter is used).
The idea behind 'worst_seek optimization' is that we limit the
cost for all non clustered ref access to the least of:
- best-rows-by-range (or all rows in no range found) / 10
- scan-time-table (roughly number of file blocks to scan table) * 3
In addition we also do not try to use rowid_filter if number of rows
estimated for 'ref' access is less than the worst_seek limitation.
The idea is that worst_seek is trying to take into account that if
we do a lot of accesses through a key, this is likely to be cached.
However it only does this for secondary keys, and not for clustered
keys or index only reads.
The effect of the worst_seek are:
- In some cases 'ref' will have a much lower cost than range or using
a clustered key.
- Some possible rowid filters for secondary keys will be ignored.
When implementing optimizer_adjust_secondary_key_costs=2, I noticed
that there is a slightly different costs for how ref+filter and
range+filter are calculated. This caused a lot of range and
range+filter to change to ref+filter, which is not good as
range+filter provides the optimizer a better estimate of how many
accepted rows there will be in the result set.
Adding a extra small cost (1 seek) when using filter mitigated the
above problems in almost all cases.
This patch should not be applied to MariaDB 11.0 as worst_seeks is
removed in 11.0 and the cost calculation for clustered keys, secondary
keys, index scan and filter is more exact.
Test case changes for --optimizer-adjust_secondary_key_costs=1
(Fix secondary key costs to be 5x of primary key):
- stat_tables_innodb:
- Complex change (probably ok as number of rows are really small)
- ref over 1 row changed to range over 10 rows with join buffer
- ref over 5 rows changed to eq_ref
- secondary ref over 1 row changed to ref of primary key over 4 rows
- Change of key to use longer key with index pushdown (a little
bit worse but not significant).
- Change to use secondary (1 row) -> primary (4 rows)
- rowid_filter_innodb:
- index_merge (2 rows) & ref (1) -> all (23 rows) -> primary eq_ref.
Test case changes for --optimizer-adjust_secondary_key_costs=2
(remove of worst_seeks & adjust filter cost):
- stat_tables_innodb:
- Join order change (probably ok as number of rows are really small)
- ref (5 rows) & ref(1 row) changed to range (10 rows & join buffer)
& eq_ref.
- selectivity_innodb:
- ref -> ref|filter (ok)
- rowid_filter_innodb:
- ref -> ref|filter (ok)
- range|filter (64 rows) changed to ref|filter (128 rows).
ok as ref|filter outputs wrong number of rows in explain.
- range, range_mrr_icp:
-ref (500 rows -> ALL (1000 rows) (ok)
- select_pkeycache, select, select_jcl6:
- ref|filter (2 rows) -> ref (2 rows) (ok)
- selectivity:
- ref -> ref_filter (ok)
- range:
- Change of 'filtered' but no stat or plan change (ok)
- selectivity:
- ref -> ref+filter (ok)
- Change of filtered but no plan change (ok)
- join_nested_jcl6:
- range -> ref|filter (ok as only 2 rows)
- subselect3, subselect3_jcl6:
- ref_or_null (4 rows) -> ALL (10 rows) (ok)
- Index_subquery (4 rows) -> ALL (10 rows) (ok)
- partition_mrr_myisam, partition_mrr_aria and partition_mrr_innodb:
- Uses ALL instead of REF for a key value that is the same for > 50%
of rows. (good)
order_by_innodb:
- range (200 rows) -> ref (20 rows)+filesort (ok)
- subselect_sj2_mat:
- One test changed. One ALL removed and replaced with eq_ref. Likely
to be better.
- join_cache:
- Changed ref over 60% of the rows to use hash join (ok)
- opt_tvc:
- Changed to use eq_ref instead of ref with plan change (probably ok)
- opt_trace:
- No worst/max seeks clipping (good).
- Almost double range_scan_time and index_scan_time (ok).
- rowid_filter:
- ref -> ref|filtered (ok)
- range|filter (77 rows) changed to ref|filter (151 rows). Proably
ok as ref|filter outputs wrong number of rows in explain.
Reviewer: Sergei Petrunia <sergey@mariadb.com>
rpl_semi_sync_slave_enabled_consistent.test and the first part of
the commit message comes from Brandon Nesterenko.
A test to show how to induce the "Read semi-sync reply magic number
error" message on a primary. In short, if semi-sync is turned on
during the hand-shake process between a primary and replica, but
later a user negates the rpl_semi_sync_slave_enabled variable while
the replica's IO thread is running; if the io thread exits, the
replica can skip a necessary call to kill_connection() in
repl_semisync_slave.slave_stop() due to its reliance on a global
variable. Then, the replica will send a COM_QUIT packet to the
primary on an active semi-sync connection, causing the magic number
error.
The test in this patch exits the IO thread by forcing an error;
though note a call to STOP SLAVE could also do this, but it ends up
needing more synchronization. That is, the STOP SLAVE command also
tries to kill the VIO of the replica, which makes a race with the IO
thread to try and send the COM_QUIT before this happens (which would
need more debug_sync to get around). See THD::awake_no_mutex for
details as to the killing of the replica’s vio.
Notes:
- The MariaDB documentation does not make it clear that when one
enables semi-sync replication it does not matter if one enables
it first in the master or slave. Any order works.
Changes done:
- The rpl_semi_sync_slave_enabled variable is now a default value for
when semisync is started. The variable does not anymore affect
semisync if it is already running. This fixes the original reported
bug. Internally we now use repl_semisync_slave.get_slave_enabled()
instead of rpl_semi_sync_slave_enabled. To check if semisync is
active on should check the @@rpl_semi_sync_slave_status variable (as
before).
- The semisync protocol conflicts in the way that the original
MySQL/MariaDB client-server protocol was designed (client-server
send and reply packets are strictly ordered and includes a packet
number to allow one to check if a packet is lost). When using
semi-sync the master and slave can send packets at 'any time', so
packet numbering does not work. The 'solution' has been that each
communication starts with packet number 1, but in some cases there
is still a chance that the packet number check can fail. Fixed by
adding a flag (pkt_nr_can_be_reset) in the NET struct that one can
use to signal that packet number checking should not be done. This
is flag is set when semi-sync is used.
- Added Master_info::semi_sync_reply_enabled to allow one to configure
some slaves with semisync and other other slaves without semisync.
Removed global variable semi_sync_need_reply that would not work
with multi-master.
- Repl_semi_sync_master::report_reply_packet() can now recognize
the COM_QUIT packet from semisync slave and not give a
"Read semi-sync reply magic number error" error for this case.
The slave will be removed from the Ack listener.
- On Windows, don't stop semisync Ack listener just because one
slave connection is using socket_id > FD_SETSIZE.
- Removed busy loop in Ack_receiver::run() by using
"Self-pipe trick" to signal new slave and stop Ack_receiver.
- Changed some Repl_semi_sync_slave functions that always returns 0
from int to void.
- Added Repl_semi_sync_slave::slave_reconnect().
- Removed dummy_function Repl_semi_sync_slave::reset_slave().
- Removed some duplicate semisync notes from the error log.
- Add test of "if (get_slave_enabled() && semi_sync_need_reply)"
before calling Repl_semi_sync_slave::slave_reply().
(Speeds up the code as we can skip all initializations).
- If epl_semisync_slave.slave_reply() fails, we disable semisync
for that connection.
- We do not call semisync.switch_off() if there are no active slaves.
Instead we check in Repl_semi_sync_master::commit_trx() if there are
no active threads. This simplices the code.
- Changed assert() to DBUG_ASSERT() to ensure that the DBUG log is
flushed in case of asserts.
- Removed the internal rpl_semi_sync_slave_status as it is not needed
anymore. The @@rpl_semi_sync_slave_status status variable is now
mapped to rpl_semi_sync_enabled.
- Removed rpl_semi_sync_slave_enabled as it is not needed anymore.
Repl_semi_sync_slave::get_slave_enabled() contains the active status.
- Added checking that we do not add a slave twice with
Ack_receiver::add_slave(). This could happen with old code.
- Removed Repl_semi_sync_master::check_and_switch() as it is not
needed anymore.
- Ensure that when we call Ack_receiver::remove_slave() that the slave
is removed from the listener before function returns.
- Call listener.listen_on_sockets() outside of mutex for better
performance and less contested mutex.
- Ensure that listening is ignoring newly added slaves when checking for
responses.
- Fixed the master ack_receiver listener is not killed if there are no
connected slaves (and thus stop semisync handling of future
connections). This could happen if all slaves sockets where would be
marked as unreliable.
- Added unlink() to base_ilist_iterator and remove() to
I_List_iterator. This enables us to remove 'dead' slaves in
Ack_recever::run().
- kill_zombie_dump_threads() now does killing of dump threads properly.
- It can now kill several threads (should be impossible but could
happen if IO slaves reconnects very fast).
- We now wait until the dump thread is done before starting the
dump.
- Added an error if kill_zombie_dump_threads() fails.
- Set thd->variables.server_id before calling
kill_zombie_dump_threads(). This simplies the code.
- Added a lot of comments both in code and tests.
- Removed DBUG_EVALUATE_IF "failed_slave_start" as it is not used.
Test changes:
- rpl.rpl_session_var2 added which runs rpl.rpl_session_var test with
semisync enabled.
- Some timings changed slight with startup of slave which caused
rpl_binlog_dump_slave_gtid_state_info.text to fail as it checked the
error log file before the slave had started properly. Fixed by
adding wait_for_pattern_in_file.inc that allows waiting for the
pattern to appear in the log file.
- Tests have been updated so that we first set
rpl_semi_sync_master_enabled on the master and then set
rpl_semi_sync_slave_enabled on the slaves (this is according to how
the MariaDB documentation document how to setup semi-sync).
- Error text "Master server does not have semi-sync enabled" has been
replaced with "Master server does not support semi-sync" for the
case when the master supports semi-sync but semi-sync is not
enabled.
Other things:
- Some trivial cleanups in Repl_semi_sync_master::update_sync_header().
- We should in 11.3 changed the default value for
rpl-semi-sync-master-wait-no-slave from TRUE to FALSE as the TRUE
does not make much sense as default. The main difference with using
FALSE is that we do not wait for semisync Ack if there are no slave
threads. In the case of TRUE we wait once, which did not bring any
notable benefits except slower startup of master configured for
using semisync.
Co-author: Brandon Nesterenko <brandon.nesterenko@mariadb.com>
This solves the problem reported in MDEV-32960 where a new
slave may not be registered in time and the master disables
semi sync because of that.
Problem:
sp_cache erroneously looked up fully qualified SP names (e.g. `DB`.`SP`),
in case insensitive style. It was wrong, because only the "name"
part is always case insensitive, while the "db" part should be compared
according to lower_case_table_names (case sensitively for 0,
case insensitively for 1 and 2).
Fix:
Adding a "casedn_name" parameter make_qname() to tell
if the name part should be lower cased:
`DB1`.`SP` -> "DB1.SP" (when casedn_name=false)
`DB1`.`SP` -> "DB1.sp" (when casedn_name=true)
and using make_qname() with casedn_name=true when creating
sp_cache hash lookup keys.
Details:
As a result, it now works as follows:
- sp_head::m_db is converted to lower case if lower_case_table_names>0
during the sp_name initialization phase. So when make_qname() is called,
sp_head::m_db is already normalized. There are no changes in here.
- The initialization phase of sp_head when creating sp_head::m_qname
now calls make_qname() with casedn_name=true,
so sp_head::m_name gets written to sp_head::m_qname in lower case.
- sp_cache_lookup() now also calls make_qname() with casedn_name=true,
so sp_head::m_name gets written to the temporary lookup key in lower case.
- sp_cache::m_hashtable now uses case sensitive comparison
Part#1 A non-functional change
Changing the signature of Identifier_chain2::make_qname() from
bool make_qname(MEM_ROOT *mem_root, LEX_CSTRING *dst) const;
to
LEX_CSTRING make_qname(MEM_ROOT *mem_root) const;
Now the result is returned as LEX_CSTRING from the function rather than
is passed as a parameter.
The return value {NULL,0} means "EOM".
This is a requirement step to fix and merge easier
MDEV-33019 The database part is not case sensitive in SP names
The original MDEV-31991 commit commend:
- Moving some of Database_qualified_name methods into a new class
Identifier_chain2.
- Changing the data type of the following variables from
Database_qualified_name to Identifier_chain2:
* q_pkg_proc in LEX::call_statement_start()
* q_pkg_func in LEX::make_item_func_call_generic()
Rationale:
The data type of Database_qualified_name::m_db will be changed
to Lex_ident_db soon. So Database_qualified_name won't be able
to store the `pkg.routine` part of `db.pkg.routine` any more,
because `pkg` must not depend on lower-case-table-names.
The reason for this change are the following:
- If we call set_killed() from one thread to kill another thread with
a message, there may be concurrent usage of the MEM_ROOT which is
not supported (this could cause memory corruption).
We do not currently have code that does this, but the API allows this
and it is better to be fix the issue before it happens.
- The per thread memory tracking does not work if one thread uses
another threads MEM_ROOT.
- set_killed() can be called if a MEM_ROOT allocation fails. In this case
it is not good to try to allocate more memory from potentially the same
MEM_ROOT.
Fix is to use my_malloc() instead of mem_root for killed messages.
This patch is actually follow-up for the task
MDEV-23902: MariaDB crash on calling function
to use correct query arena for a statement. In case invocation of
a function is in progress use its call arena, else use current
query arena that can be either a statement or a regular query arena.
Checking for kill with thd_kill_level() or check_killed() runs apc
requests, which takes the LOCK_thd_kill mutex. But this is dangerous,
as checking for kill needs to be called while holding many different
mutexes, and can lead to cyclic mutex dependency and deadlock.
But running apc is only "best effort", so skip running the apc if the
LOCK_thd_kill is not available. The apc will then be run on next check
of kill signal.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
In some cases "SHOW PROCESSLIST" could show "Reset for next command"
as State, even if the previous query had finished properly.
Fixed by clearing State after end of command and also setting the State
for the "Connect" command.
Other things:
- Changed usage of 'thd->set_command(COM_SLEEP)' to
'thd->mark_connection_idle()'.
- Changed thread_state_info() to return "" instead of NULL. This is
just a safety measurement and in line with the logic of the
rest of the function.
Binary logging is now disabled for the queries run by SQL SERVICE.
The binlogging can be turned on with the 'SET SQL_LOG_BIN=On' query.
Conflicts:
sql/sql_prepare.cc
Conflicts:
sql/sql_prepare.cc
This allows a user to to change the default value of MAX_SEL_ARGS (16000)
in the rare case where they neeed more generated SEL_ARGS (as part of
the range optimizer)
Raise notes if indexes cannot be used:
- in case of data type or collation mismatch (diferent error messages).
- in case if a table field was replaced to something else
(e.g. Item_func_conv_charset) during a condition rewrite.
Added option to write warnings and notes to the slow query log for
slow queries.
New variables added/changed:
- note_verbosity, with is a set of the following options:
basic - All old notes
unusable_keys - Print warnings about keys that cannot be used
for select, delete or update.
explain - Print unusable_keys warnings for EXPLAIN querys.
The default is 'basic,explain'. This means that for old installations
the only notable new behavior is that one will get notes about
unusable keys when one does an EXPLAIN for a query. One can turn all
of all notes by either setting note_verbosity to "" or setting sql_notes=0.
- log_slow_verbosity has a new option 'warnings'. If this is set
then warnings and notes generated are printed in the slow query log
(up to log_slow_max_warnings times per statement).
- log_slow_max_warnings - Max number of warnings written to
slow query log.
Other things:
- One can now use =ALL for any 'set' variable to set all options at once.
For example using "note_verbosity=ALL" in a config file or
"SET @@note_verbosity=ALL' in SQL.
- mysqldump will in the future use @@note_verbosity=""' instead of
@sql_notes=0 to disable notes.
- Added "enum class Data_type_compatibility" and changing the return type
of all Field::can_optimize*() methods from "bool" to this new data type.
Reviewer & Co-author: Alexander Barkov <bar@mariadb.com>
- The code that prints out the notes comes mainly from Alexander
Example of what causes the problem:
T1: ANALYZE TABLE starts to collect statistics
T2: ALTER TABLE starts by deleting statistics for all changed fields,
then creates a temp table and copies data to it.
T1: ANALYZE ends and writes to the statistics tables.
T2: ALTER TABLE renames temp table in place of the old table.
Now the statistics from analyze matches the old deleted tables.
Fixed by waiting to delete old statistics until ALTER TABLE is
the only one using the old table and ensure that rename of columns
can handle swapping of column names.
rename_columns_in_stat_table() (former rename_column_in_stat_tables())
now takes a list of columns to rename. It uses the following algorithm
to update column_stats to be able to handle circular renames
- While there are columns to be renamed and it is the first loop or
last rename loop did change something.
- Loop over all columns to be renamed
- Change column name in column_stat
- If fail because of duplicate key
- If this is first change attempt for this column
- Change column name to a temporary column name
- If there was a conflicting row, replace it with the current row.
else
- Remove entry from column list
- Loop over all remaining columns in the list
- Remove the conflicting row
- Change column from temporary name to final name in column_stat
Other things:
- Don't flush tables for every operation. Only flush when all updates
are done.
- Rename of columns was not handled in case of ALGORITHM=copy (old bug).
- Fixed that we do not collect statistics for hidden hash columns
used by UNIQUE constraint on long values.
- Fixed that we do not collect statistics for blob columns referred by
generated virtual columns. This was achieved by storing the fields for
which we want to have statistics in table->has_value_set instead of
in table->read_set.
- Rename of indexes was not handled for persistent statistics.
- This is now handled similar as rename of columns. Renamed columns
are now stored in 'rename_stat_indexes' and handled in
Alter_info::delete_statistics() together with drooped indexes.
- ALTER TABLE .. ADD INDEX may instead of creating a new index rename
an existing generated foreign key index. This was not reflected in
the index_stats table because this was handled in
mysql_prepare_create_table instead instead of in the mysql_alter() code.
Fixed by adding a call in mysql_prepare_create_table() to drop the
changed index.
I also had to change the code that 'marked the index' to be ignored
with code that would not destroy the original index name.
Reviewer: Sergei Petrunia <sergey@mariadb.com>
At the moment we cannot support
wsrep_forced_binlog_format=[MIXED|STATEMENT]
during CREATE TABLE AS SELECT.
Statement will use ROW instead and give
a warning.
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
On creation of a VIEW that depends on a stored routine an instance of
the class Item_func_sp is allocated on a memory root of SP statement.
It happens since mysql_make_view() calls the method
THD::activate_stmt_arena_if_needed()
before parsing definition of the view.
On the other hand, when sp_head's rcontext is created an instance of
the class Field referenced by the data member
Item_func_sp::result_field
is allocated on the Item_func_sp's Query_arena (call arena) that set up
inside the method
Item_sp::execute_impl
just before calling the method
sp_head::execute_function()
On return from the method sp_head::execute_function() all items allocated
on the Item_func_sp's Query_arena are released and its memory root is freed
(see implementation of the method Item_sp::execute_impl). As a consequence,
the pointer
Item_func_sp::result_field
references to the deallocated memory. Later, when the method
sp_head::execute
cleans up items allocated for just executed SP instruction the method
Item_func_sp::cleanup is invoked and tries to delete an object referenced
by data member Item_func_sp::result_field that points to already deallocated
memory, that results in a server abnormal termination.
To fix the issue the current active arena shouldn't be switched to
a statement arena inside the function mysql_make_view() that invoked indirectly
by the method sp_head::rcontext_create. It is implemented by introducing
the new Query_arena's state STMT_SP_QUERY_ARGUMENTS that is set when explicit
Query_arena is created for placing SP arguments and other caller's side items
used during SP execution. Then the method THD::activate_stmt_arena_if_needed()
checks Query_arena's state and returns immediately without switching to
statement's arena.
The problem was that parallel replication of temporary tables using
statement-based binlogging could overlap the COMMIT in one thread with a DML
or DROP TEMPORARY TABLE in another thread using the same temporary table.
Temporary tables are not safe for concurrent access, so this caused
reference to freed memory and possibly other nastiness.
The fix is to disable the optimisation with overlapping commits of one
transaction with the start of a later transaction, when temporary tables are
in use. Then the following event groups will be blocked from starting until
the one using temporary tables is completed.
This also fixes occasional test failures of rpl.rpl_parallel_temptable seen
in Buildbot.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
mark old keys in the ALTER TABLE with the `old` flag, not with
the `key_create_info.check_for_duplicate_indexes`.
This allows to mark old foreign keys too.
ANALYZE FORMAT=JSON output now includes table.r_engine_stats which
has the engine statistics. Only non-zero members are printed.
Internally: EXPLAIN data structures Explain_table_acccess and
Explain_update now have handler* handler_for_stats pointer.
It is used to read statistics from handler_for_stats->handler_stats.
The following applies only to 10.9+, backport doesn't use it:
Explain data structures exist after the tables are closed. We avoid
walking invalid pointers using this:
- SQL layer calls Explain_query::notify_tables_are_closed() before
closing tables.
- After that call, printing of JSON output is disabled. Non-JSON output
can be printed but we don't access handler_for_stats when doing that.
- Moving the code from a public function trim_whitespaces()
to the class Lex_cstring as methods. This code may
be useful in other contexts, and also this code becomes
visible inside sql_class.h
- Adding a helper method THD::strmake_lex_cstring_trim_whitespaces()
- Unifying the way how CREATE PROCEDURE/CREATE FUNCTION and
CREATE PACKAGE/CREATE PACKAGE BODY work:
a) Now CREATE PACKAGE/CREATE PACKAGE BODY also calls
Lex->sphead->set_body_start() to remember the cpp body start inside
an sp_head member.
b) adding a "const char *cpp_body_end" parameter to
sp_head::set_stmt_end().
These changes made it possible to reuse sp_head::set_stmt_end() inside
LEX::create_package_finalize() and remove the duplucate code.
- Renaming sp_head::m_body_begin to m_cpp_body_begin and adding a comment
to make it clear that this member is used only during parsing, and
points to a fragment inside the cpp buffer.
- Changed sp_head::set_body_start() and sp_head::set_stmt_end()
to skip the calls related to "body_utf8" in cases when m_parent is not NULL.
A non-NULL m_parent means that we're inside a package routine.
"body_utf8" in such case belongs not to the current sphead itself,
but to parent (the package) sphead.
So an sphead instance of a package routine should neither initialize,
nor finalize, nor change in any other ways the "body_utf8" related
members of Lex_input_stream, and should not take over or copy "body_utf8"
data from Lex_input_stream to "this".
The problem is that when a worker thread is (user) killed in
wait_for_prior_commit, the event group may complete out-of-order since the
wait for prior commit was aborted by the kill.
This fix ensures that event groups will always complete in-order, even
in the error case. This is done in finish_event_group() by doing an
extra wait_for_prior_commit(), if necessary, that ignores kills.
This fix supersedes the fix for MDEV-30780, so the earlier fix for
that is reverted in this patch.
Also fix that an error from wait_for_prior_commit() inside
finish_event_group() would not signal the error to
wakeup_subsequent_commits().
Based on earlier work by Brandon Nesterenko and Andrei Elkin, with
some changes to simplify the semantics of wait_for_prior_commit() and
make the code more robust to future changes.
Reviewed-by: Andrei Elkin <andrei.elkin@mariadb.com>
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
Where a read-only server permits writes through replication, it
should not permit user connections to commit/rollback XA
transactions prepared via replication. The bug reported in
MDEV-30978 shows that this can happen. This is because there is no
read only check in the XA transaction logic, the most relevant one
occurs in ha_commit_trans() for normal statements/transactions.
This patch extends the XA transaction logic to check the read only
status of the server before performing an XA COMMIT or ROLLBACK.
Reviewed By:
Andrei Elkin <andrei.elkin@mariadb.com>
The new statistics is enabled by adding the "engine", "innodb" or "full"
option to --log-slow-verbosity
Example output:
# Pages_accessed: 184 Pages_read: 95 Pages_updated: 0 Old_rows_read: 1
# Pages_read_time: 17.0204 Engine_time: 248.1297
Page_read_time is time doing physical reads inside a storage engine.
(Writes cannot be tracked as these are usually done in the background).
Engine_time is the time spent inside the storage engine for the full
duration of the read/write/update calls. It uses the same code as
'analyze statement' for calculating the time spent.
The engine statistics is done with a generic interface that should be
easy for any engine to use. It can also easily be extended to provide
even more statistics.
Currently only InnoDB has counters for Pages_% and Undo_% status.
Engine_time works for all engines.
Implementation details:
class ha_handler_stats holds all engine stats. This class is included
in handler and THD classes.
While a query is running, all statistics is updated in the handler. In
close_thread_tables() the statistics is added to the THD.
handler::handler_stats is a pointer to where statistics should be
collected. This is set to point to handler::active_handler_stats if
stats are requested. If not, it is set to 0.
handler_stats has also an element, 'active' that is 1 if stats are
requested. This is to allow engines to avoid doing any 'if's while
updating the statistics.
Cloned or partition tables have the pointer set to the base table if
status are requested.
There is a small performance impact when using --log-slow-verbosity=engine:
- All engine calls in 'select' will be timed.
- IO calls for InnoDB reads will be timed.
- Incrementation of counters are done on local variables and accesses
are inline, so these should have very little impact.
- Statistics has to be reset for each statement for the THD and each
used handler. This is only 40 bytes, which should be neglectable.
- For partition tables we have to loop over all partitions to update
the handler_status as part of table_init(). Can be optimized in the
future to only do this is log-slow-verbosity changes. For this to work
we have to update handler_status for all opened partitions and
also for all partitions opened in the future.
Other things:
- Added options 'engine' and 'full' to log-slow-verbosity.
- Some of the new files in the test suite comes from Percona server, which
has similar status information.
- buf_page_optimistic_get(): Do not increment any counter, since we are
only validating a pointer, not performing any buf_pool.page_hash lookup.
- Added THD argument to save_explain_data_intern().
- Switched arguments for save_explain_.*_data() to have
always THD first (generates better code as other functions also have THD
first).
The problem is that a parallel replica would not immediately stop
running/queued transactions when issued STOP SLAVE. That is, it
allowed the current group of transactions to run, and sometimes the
transactions which belong to the next group could be started and run
through commit after STOP SLAVE was issued too, if the last group
had started committing. This would lead to long periods to wait for
all waiting transactions to finish.
This patch updates a parallel replica to try and abort immediately
and roll-back any ongoing transactions. The exception to this is any
transactions which are non-transactional (e.g. those modifying
sequences or non-transactional tables), and any prior transactions,
will be run to completion.
The specifics are as follows:
1. A new stage was added to SHOW PROCESSLIST output for the SQL
Thread when it is waiting for a replica thread to either rollback or
finish its transaction before stopping. This stage presents as
“Waiting for worker thread to stop”
2. Worker threads which error or are killed no longer perform GCO
cleanup if there is a concurrently running prior transaction. This
is because a worker thread scheduled to run in a future GCO could be
killed and incorrectly perform cleanup of the active GCO.
3. Refined cases when the FL_TRANSACTIONAL flag is added to GTID
binlog events to disallow adding it to transactions which modify
both transactional and non-transactional engines when the binlogging
configuration allow the modifications to exist in the same event,
i.e. when using binlog_direct_non_trans_update == 0 and
binlog_format == statement.
4. A few existing MTR tests relied on the completion of certain
transactions after issuing STOP SLAVE, and were re-recorded
(potentially with added synchronizations) under the new rollback
behavior.
Reviewed By
===========
Andrei Elkin <andrei.elkin@mariadb.com>
This commit contains a merge from 10.5-MDEV-29293-squash
into 10.6.
Although the bug MDEV-29293 was not reproducible with 10.6,
the fix contains several improvements for wsrep KILL query and
BF abort handling, and addresses the following issues:
* MDEV-30307 KILL command issued inside a transaction is
problematic for galera replication:
This commit will remove KILL TOI replication, so Galera side
transaction context is not lost during KILL.
* MDEV-21075 KILL QUERY maintains nodes data consistency but
breaks GTID sequence: This is fixed as well as KILL does not
use TOI, and thus does not change GTID state.
* MDEV-30372 Assertion in wsrep-lib state: This was caused by
BF abort or KILL when local transaction was in the middle
of group commit. This commit disables THD::killed handling
during commit, so the problem is avoided.
* MDEV-30963 Assertion failure !lock.was_chosen_as_deadlock_victim
in trx0trx.h:1065: The assertion happened when the victim was
BF aborted via MDL while it was committing. This commit changes
MDL BF aborts so that transactions which are committing cannot
be BF aborted via MDL. The RQG grammar attached in the issue
could not reproduce the crash anymore.
Original commit message from 10.5 fix:
MDEV-29293 MariaDB stuck on starting commit state
The problem seems to be a deadlock between KILL command execution
and BF abort issued by an applier, where:
* KILL has locked victim's LOCK_thd_kill and LOCK_thd_data.
* Applier has innodb side global lock mutex and victim trx mutex.
* KILL is calling innobase_kill_query, and is blocked by innodb
global lock mutex.
* Applier is in wsrep_innobase_kill_one_trx and is blocked by
victim's LOCK_thd_kill.
The fix in this commit removes the TOI replication of KILL command
and makes KILL execution less intrusive operation. Aborting the
victim happens now by using awake_no_mutex() and ha_abort_transaction().
If the KILL happens when the transaction is committing, the
KILL operation is postponed to happen after the statement
has completed in order to avoid KILL to interrupt commit
processing.
Notable changes in this commit:
* wsrep client connections's error state may remain sticky after
client connection is closed. This error message will then pop
up for the next client session issuing first SQL statement.
This problem raised with test galera.galera_bf_kill.
The fix is to reset wsrep client error state, before a THD is
reused for next connetion.
* Release THD locks in wsrep_abort_transaction when locking
innodb mutexes. This guarantees same locking order as with applier
BF aborting.
* BF abort from MDL was changed to do BF abort on server/wsrep-lib
side first, and only then do the BF abort on InnoDB side. This
removes the need to call back from InnoDB for BF aborts which originate
from MDL and simplifies the locking.
* Removed wsrep_thd_set_wsrep_aborter() from service_wsrep.h.
The manipulation of the wsrep_aborter can be done solely on
server side. Moreover, it is now debug only variable and
could be excluded from optimized builds.
* Remove LOCK_thd_kill from wsrep_thd_LOCK/UNLOCK to allow more
fine grained locking for SR BF abort which may require locking
of victim LOCK_thd_kill. Added explicit call for
wsrep_thd_kill_LOCK/UNLOCK where appropriate.
* Wsrep-lib was updated to version which allows external
locking for BF abort calls.
Changes to MTR tests:
* Disable galera_bf_abort_group_commit. This test is going to
be removed (MDEV-30855).
* Make galera_var_retry_autocommit result more readable by echoing
cases and expectations into result. Only one expected result for
reap to verify that server returns expected status for query.
* Record galera_gcache_recover_manytrx as result file was incomplete.
Trivial change.
* Make galera_create_table_as_select more deterministic:
Wait until CTAS execution has reached MDL wait for multi-master
conflict case. Expected error from multi-master conflict is
ER_QUERY_INTERRUPTED. This is because CTAS does not yet have open
wsrep transaction when it is waiting for MDL, query gets interrupted
instead of BF aborted. This should be addressed in separate task.
* A new test galera_bf_abort_registering to check that registering trx gets
BF aborted through MDL.
* A new test galera_kill_group_commit to verify correct behavior
when KILL is executed while the transaction is committing.
Co-authored-by: Seppo Jaakola <seppo.jaakola@iki.fi>
Co-authored-by: Jan Lindström <jan.lindstrom@galeracluster.com>
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
The problem seems to be a deadlock between KILL command execution
and BF abort issued by an applier, where:
* KILL has locked victim's LOCK_thd_kill and LOCK_thd_data.
* Applier has innodb side global lock mutex and victim trx mutex.
* KILL is calling innobase_kill_query, and is blocked by innodb
global lock mutex.
* Applier is in wsrep_innobase_kill_one_trx and is blocked by
victim's LOCK_thd_kill.
The fix in this commit removes the TOI replication of KILL command
and makes KILL execution less intrusive operation. Aborting the
victim happens now by using awake_no_mutex() and ha_abort_transaction().
If the KILL happens when the transaction is committing, the
KILL operation is postponed to happen after the statement
has completed in order to avoid KILL to interrupt commit
processing.
Notable changes in this commit:
* wsrep client connections's error state may remain sticky after
client connection is closed. This error message will then pop
up for the next client session issuing first SQL statement.
This problem raised with test galera.galera_bf_kill.
The fix is to reset wsrep client error state, before a THD is
reused for next connetion.
* Release THD locks in wsrep_abort_transaction when locking
innodb mutexes. This guarantees same locking order as with applier
BF aborting.
* BF abort from MDL was changed to do BF abort on server/wsrep-lib
side first, and only then do the BF abort on InnoDB side. This
removes the need to call back from InnoDB for BF aborts which originate
from MDL and simplifies the locking.
* Removed wsrep_thd_set_wsrep_aborter() from service_wsrep.h.
The manipulation of the wsrep_aborter can be done solely on
server side. Moreover, it is now debug only variable and
could be excluded from optimized builds.
* Remove LOCK_thd_kill from wsrep_thd_LOCK/UNLOCK to allow more
fine grained locking for SR BF abort which may require locking
of victim LOCK_thd_kill. Added explicit call for
wsrep_thd_kill_LOCK/UNLOCK where appropriate.
* Wsrep-lib was updated to version which allows external
locking for BF abort calls.
Changes to MTR tests:
* Disable galera_bf_abort_group_commit. This test is going to
be removed (MDEV-30855).
* Record galera_gcache_recover_manytrx as result file was incomplete.
Trivial change.
* Make galera_create_table_as_select more deterministic:
Wait until CTAS execution has reached MDL wait for multi-master
conflict case. Expected error from multi-master conflict is
ER_QUERY_INTERRUPTED. This is because CTAS does not yet have open
wsrep transaction when it is waiting for MDL, query gets interrupted
instead of BF aborted. This should be addressed in separate task.
* A new test galera_kill_group_commit to verify correct behavior
when KILL is executed while the transaction is committing.
Co-authored-by: Seppo Jaakola <seppo.jaakola@iki.fi>
Co-authored-by: Jan Lindström <jan.lindstrom@galeracluster.com>
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
This is a backport from 10.5.
The problem seems to be a deadlock between KILL command execution
and BF abort issued by an applier, where:
* KILL has locked victim's LOCK_thd_kill and LOCK_thd_data.
* Applier has innodb side global lock mutex and victim trx mutex.
* KILL is calling innobase_kill_query, and is blocked by innodb
global lock mutex.
* Applier is in wsrep_innobase_kill_one_trx and is blocked by
victim's LOCK_thd_kill.
The fix in this commit removes the TOI replication of KILL command
and makes KILL execution less intrusive operation. Aborting the
victim happens now by using awake_no_mutex() and ha_abort_transaction().
If the KILL happens when the transaction is committing, the
KILL operation is postponed to happen after the statement
has completed in order to avoid KILL to interrupt commit
processing.
Notable changes in this commit:
* wsrep client connections's error state may remain sticky after
client connection is closed. This error message will then pop
up for the next client session issuing first SQL statement.
This problem raised with test galera.galera_bf_kill.
The fix is to reset wsrep client error state, before a THD is
reused for next connetion.
* Release THD locks in wsrep_abort_transaction when locking
innodb mutexes. This guarantees same locking order as with applier
BF aborting.
* BF abort from MDL was changed to do BF abort on server/wsrep-lib
side first, and only then do the BF abort on InnoDB side. This
removes the need to call back from InnoDB for BF aborts which originate
from MDL and simplifies the locking.
* Removed wsrep_thd_set_wsrep_aborter() from service_wsrep.h.
The manipulation of the wsrep_aborter can be done solely on
server side. Moreover, it is now debug only variable and
could be excluded from optimized builds.
* Remove LOCK_thd_kill from wsrep_thd_LOCK/UNLOCK to allow more
fine grained locking for SR BF abort which may require locking
of victim LOCK_thd_kill. Added explicit call for
wsrep_thd_kill_LOCK/UNLOCK where appropriate.
* Wsrep-lib was updated to version which allows external
locking for BF abort calls.
Changes to MTR tests:
* Disable galera_bf_abort_group_commit. This test is going to
be removed (MDEV-30855).
* Record galera_gcache_recover_manytrx as result file was incomplete.
Trivial change.
* Make galera_create_table_as_select more deterministic:
Wait until CTAS execution has reached MDL wait for multi-master
conflict case. Expected error from multi-master conflict is
ER_QUERY_INTERRUPTED. This is because CTAS does not yet have open
wsrep transaction when it is waiting for MDL, query gets interrupted
instead of BF aborted. This should be addressed in separate task.
* A new test galera_kill_group_commit to verify correct behavior
when KILL is executed while the transaction is committing.
Co-authored-by: Seppo Jaakola <seppo.jaakola@iki.fi>
Co-authored-by: Jan Lindström <jan.lindstrom@galeracluster.com>
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
