This task involves the implementation for the optimizer trace.
This feature produces a trace for any SELECT/UPDATE/DELETE/,
which contains information about decisions taken by the optimizer during
the optimization phase (choice of table access method, various costs,
transformations, etc). This feature would help to tell why some decisions were
taken by the optimizer and why some were rejected.
Trace is session-local, controlled by the @@optimizer_trace variable.
To enable optimizer trace we need to write:
set @@optimizer_trace variable= 'enabled=on';
To display the trace one can run:
SELECT trace FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE;
This task also involves:
MDEV-18489: Limit the memory used by the optimizer trace
introduces a switch optimizer_trace_max_mem_size which limits
the memory used by the optimizer trace. This was implemented by
Sergei Petrunia.
introduce the syntax
... IDENTIFIED { WITH | VIA }
plugin [ { USING | AS } auth ]
[ OR plugin [ { USING | AS } auth ]
[ OR ... ]]
Server will try auth plugins in the specified order until the first
success. No protocol changes, server uses the existing "switch plugin"
packet.
The auth chain is stored in json as
"auth_or":[{"plugin":"xxx","authentication_string":"yyy"},
{},
{"plugin":"foo","authentication_string":"bar"},
...],
"plugin":"aaa", "authentication_string":"bbb"
Note:
* "auth_or" implies that there might be "auth_and" someday;
* one entry in the array is an empty object, meaning to take plugin/auth
from the main json object. This preserves compatibility with
the existing mysql.global_priv table and with the mysql.user view.
This entry is preferrably a mysql_native_password plugin for a
non-empty mysql.user.password column.
SET PASSWORD is supported and changes the password for the *first*
plugin in the chain that has a notion of a "password"
Implemented and integrated THD_list as a replacement for the global
thread list. It uses own mutex instead of LOCK_thread_count for THD
list protection.
Removed unused first_global_thread() and next_global_thread().
delayed_insert_threads is now protected by LOCK_delayed_insert. Although
this patch doesn't fix very wrong synchronization of this variable.
After this patch there are only 2 legitimate uses of LOCK_thread_count
left, both in mysqld.cc: thread_count and ready_to_exit.
Aim is to reduce usage of LOCK_thread_count and COND_thread_count.
Part of MDEV-15135.
Bootstrap in a separate thread was introduced in 746f0b3b7 to workaround
OS/2 small stack size. OS/2 support was discontinued in 2006 and modern
operating systems have default stack size a few times larger than
default thread_stack and it is tunable.
Aim is to reduce usage of LOCK_thread_count and COND_thread_count.
Part of MDEV-15135.
Part of MDEV-5336 Implement LOCK FOR BACKUP
- Changed check of Global_only_lock to also include BACKUP lock.
- We store latest MDL_BACKUP_DDL lock in thd->mdl_backup_ticket to be able
to downgrade lock during copy_data_between_tables()
- Re-numbered enum_table_category to make some tests easier
- Moved TABLE_CATEGORY_INFORMATION to be first CATEGORY of virtual tables
- Don't take MDL locks for not updateable table category's
Part of MDEV-5336 Implement LOCK FOR BACKUP
The idea is that instead of waiting in close_cached_tables() for all
tables to be closed, we instead call flush_tables() that does:
- Flush not used objects in table cache to free memory
- Collect all tables that are open
- Call HA_EXTRA_FLUSH on the objects, to get them into "closed state"
- Added HA_EXTRA_FLUSH support to archive and CSV
- Added multi-user protection to HA_EXTRA_FLUSH in MyISAM and Aria
The benefit compared to old code is:
- FTWRL doesn't have to wait for long running read operations or
open HANDLER's
- The old code used the original create_info from lex, not the new one
that includes more information (like OPT_OR_REPLACE).
The bug was not discovered as the code in lock_table_named() only
checked for OPT_OR_REPLACE in case of timeout errors.
As lock_table_names will be fixed as part of BACKUP STAGE's, there
is no changes in lock_table_names() in this commit.
- Removed also the 'temporary' copy of statement flags to thd for
lock_table_names()
main.derived_cond_pushdown: Move all 10.3 tests to the end,
trim trailing white space, and add an "End of 10.3 tests" marker.
Add --sorted_result to tests where the ordering is not deterministic.
main.win_percentile: Add --sorted_result to tests where the
ordering is no longer deterministic.
sql\sql_acl.cc(3114): error C2220: warning treated as error - no 'object' file generated
sql\sql_acl.cc(3114): warning C4390: ';': empty controlled statement found; is this the intent?
- Changed ERROR to WARNING for MyISAM/Aria message
that are warnings in the check utilities.
This affects for example "client is using or
hasn't closed the table properly".
- Print "Table is fixed" if check succeded in
fixing the table.
Implement according to standard SQL specification 2008.
The check_constraints table is used for fetching metadata about
the constraints defined for tables in all databases.
