This patch fixes two problems that may arise when changing the
value of wsrep_slave_threads:
1) Threads may be leaked if wsrep_slave_threads is changed
repeatedly. Specifically, when changing the number of slave
threads, we keep track of wsrep_slave_count_change, the
number of slaves to start / stop. The problem arises when
wsrep_slave_count_change is updated before slaves had a
chance to exit (threads may take some time to exit, as they
exit only after commiting one more replication event).
The fix is to update wsrep_slave_count_change such that it
reflects the number of threads that already exited or are
scheduled to exit.
2) Attempting to set out of range value for wsrep_slave_threads
(below 1 / above 512) results in wsrep_slave_count_change to
be computed based on the out of range value, even though a
warning is generated and wsrep_slave_threads is set to a
truncated value. wsrep_slave_count_change is computed in
wsrep_slave_threads_check(), which is called before mysql
checks for valid range. Fix is to update wsrep_count_change
whenever wsrep_slave_threads is updated with a valid value.
"Optimization for equi-joins of derived tables with GROUP BY"
should be considered rather as a 'proof of concept'.
The task itself is targeted at an optimization that employs re-writing
equi-joins with grouping derived tables / views into lateral
derived tables. Here's an example of such transformation:
select t1.a,t.max,t.min
from t1 [left] join
(select a, max(t2.b) max, min(t2.b) min from t2
group by t2.a) as t
on t1.a=t.a;
=>
select t1.a,tl.max,tl.min
from t1 [left] join
lateral (select a, max(t2.b) max, min(t2.b) min from t2
where t1.a=t2.a) as t
on 1=1;
The transformation pushes the equi-join condition t1.a=t.a into the
derived table making it dependent on table t1. It means that for
every row from t1 a new derived table must be filled out. However
the size of any of these derived tables is just a fraction of the
original derived table t. One could say that transformation 'splits'
the rows used for the GROUP BY operation into separate groups
performing aggregation for a group only in the case when there is
a match for the current row of t1.
Apparently the transformation may produce a query with a better
performance only in the case when
- the GROUP BY list refers only to fields returned by the derived table
- there is an index I on one of the tables T used in FROM list of
the specification of the derived table whose prefix covers the
the fields from the proper beginning of the GROUP BY list or
fields that are equal to those fields.
Whether the result of the re-writing can be executed faster depends
on many factors:
- the size of the original derived table
- the size of the table T
- whether the index I is clustering for table T
- whether the index I fully covers the GROUP BY list.
This patch only tries to improve the chosen execution plan using
this transformation. It tries to do it only when the chosen
plan reaches the derived table by a key whose prefix covers
all the fields of the derived table produced by the fields of
the table T from the GROUP BY list.
The code of the patch does not evaluates the cost of the improved
plan. If certain conditions are met the transformation is applied.
- Added variable tmp_disk_table_size
- Added variable tmp_memory_table_size as an alias for tmp_table_size
- Changed internal variable tmp_table_size to tmp_memory_table_size
- create_info.data_file_length is now set with tmp_disk_table_size
- Fixed that Aria doesn't reset max_data_file_length for internal tables
- Added status flag if table is full so that we can detect this on next insert.
This ensures that the table is always 'correct', but we get the error one
row after the row that grow the table too big.
- Removed some mutex lock for internal temporary tables
When WSREP(thd) is not true we will use my_error(...) to print error. This
will set thd->is_error() to true and we wont be getting generic error.
Signed-off-by: Sachin Setiya <sachin.setiya@mariadb.com>
Benefits of this patch:
- Removed a lot of calls to strlen(), especially for field_string
- Strings generated by parser are now const strings, less chance of
accidently changing a string
- Removed a lot of calls with LEX_STRING as parameter (changed to pointer)
- More uniform code
- Item::name_length was not kept up to date. Now fixed
- Several bugs found and fixed (Access to null pointers,
access of freed memory, wrong arguments to printf like functions)
- Removed a lot of casts from (const char*) to (char*)
Changes:
- This caused some ABI changes
- lex_string_set now uses LEX_CSTRING
- Some fucntions are now taking const char* instead of char*
- Create_field::change and after changed to LEX_CSTRING
- handler::connect_string, comment and engine_name() changed to LEX_CSTRING
- Checked printf() related calls to find bugs. Found and fixed several
errors in old code.
- A lot of changes from LEX_STRING to LEX_CSTRING, especially related to
parsing and events.
- Some changes from LEX_STRING and LEX_STRING & to LEX_CSTRING*
- Some changes for char* to const char*
- Added printf argument checking for my_snprintf()
- Introduced null_clex_str, star_clex_string, temp_lex_str to simplify
code
- Added item_empty_name and item_used_name to be able to distingush between
items that was given an empty name and items that was not given a name
This is used in sql_yacc.yy to know when to give an item a name.
- select table_name."*' is not anymore same as table_name.*
- removed not used function Item::rename()
- Added comparision of item->name_length before some calls to
my_strcasecmp() to speed up comparison
- Moved Item_sp_variable::make_field() from item.h to item.cc
- Some minimal code changes to avoid copying to const char *
- Fixed wrong error message in wsrep_mysql_parse()
- Fixed wrong code in find_field_in_natural_join() where real_item() was
set when it shouldn't
- ER_ERROR_ON_RENAME was used with extra arguments.
- Removed some (wrong) ER_OUTOFMEMORY, as alloc_root will already
give the error.
TODO:
- Check possible unsafe casts in plugin/auth_examples/qa_auth_interface.c
- Change code to not modify LEX_CSTRING for database name
(as part of lower_case_table_names)
Intermediate commit.
Fix engine list lifetime for sys_var_pluginlist.
The Sys_var class assumes that some operations can be done without
explicitly freeing resources, for example default_value_ptr(). Thus,
methods (like Sys_var_pluginlist::do_check) need to generally work
with temporary lists, which are registered in the THD to be
freed/unlocked automatically. And do_update() needs to make a
permanent copy to store in the global variable.
Intermediate commit.
Implement a --gtid-pos-auto-engines system variable. The variable is a list
of engines for which mysql.gtid_slave_pos_ENGINE should be auto-created if
needed.
This commit only implements the option variable. It is not yet used to
actually auto-create any tables, nor is there a corresponding command-line
version of the option yet.
Terminate idle transactions safely in server layer by setting up socket timeout
parameter. Percona provides another patch to resolve similar problem, but it
calls server layer's callback in InnoDB plugin to close THD, which crashes in
some testcases. See https://bugs.launchpad.net/percona-server/+bug/901060 for
more detailed information.
1. export parameter trx_idle_timeout to handle all kinds of transactions, the priority is highest
2. export parameter trx_readonly_idle_timeout to handle read-only transactions
3. export parameter trx_changes_idle_timeout to handle read-write transactions
Extended syntax so that it is now possible to set lock_wait_timeout for the
following statements:
SELECT ... FOR UPDATE [WAIT n|NOWAIT]
SELECT ... LOCK IN SHARED MODE [WAIT n|NOWAIT]
LOCK TABLE ... [WAIT n|NOWAIT]
CREATE ... INDEX ON tbl_name (index_col_name, ...) [WAIT n|NOWAIT] ...
ALTER TABLE tbl_name [WAIT n|NOWAIT] ...
OPTIMIZE TABLE tbl_name [WAIT n|NOWAIT]
DROP INDEX ... [WAIT n|NOWAIT]
TRUNCATE TABLE tbl_name [WAIT n|NOWAIT]
RENAME TABLE tbl_name [WAIT n|NOWAIT] ...
DROP TABLE tbl_name [WAIT n|NOWAIT] ...
Valid range of lock_wait_timeout and innodb_lock_wait_timeout was extended so
that 0 is acceptable value (means no wait).
This is amended AliSQL patch. We prefer Oracle syntax for [WAIT n|NOWAIT]
instead of original [WAIT [n]|NO_WAIT].
Define my_thread_id as an unsigned type, to avoid mismatch with
ulonglong. Change some parameters to this type.
Use size_t in a few more places.
Declare many flag constants as unsigned to avoid sign mismatch
when shifting bits or applying the unary ~ operator.
When applying the unary ~ operator to enum constants, explictly
cast the result to an unsigned type, because enum constants can
be treated as signed.
In InnoDB, change the source code line number parameters from
ulint to unsigned type. Also, make some InnoDB functions return
a narrower type (unsigned or uint32_t instead of ulint;
bool instead of ibool).
