WITH A VARIABLE AND ORDER BY
Bug#16035412 MYSQL SERVER 5.5.29 WRONG SORTING USING COMPLEX INDEX
This is a fix for a regression introduced by Bug#12667154:
Bug#12667154 attempted to fix a performance problem with subqueries
that did filesort. For doing filesort, the optimizer creates a quick
select object to use when building the sort index. This quick select
object was deleted after the first call to create_sort_index(). Thus,
for queries where the subquery was executed multiple times, the quick
object was only used for the first execution. For all later executions
of the subquery, filesort used a complete table scan for building the
sort index. The fix for Bug#12667154 tried to fix this by not deleting
the quick object after the first execution of create_sort_index() so
that it would be re-used for building the sort index by the following
executions of the subquery.
This regression introduced in Bug#12667154 is that due to not deleting
the quick select object after building the sort index, the quick
object could in some cases be used also during the second phase of the
execution of the subquery instead of using the created sort
index. This caused wrong results to be returned.
The fix for this issue is to delete the reference to the select object
after it has been used in create_sort_index(). In this way the select
and quick objects will not be available when doing the second phase
of the execution of the select operation. To ensure that the select
object can be re-used for the following executions of the subquery
we make a copy of the select pointer. This is used for restoring the
select object after the select operation is completed.
mysql-test/suite/innodb/r/innodb_mysql.result:
Changed explain output: The explain now contains "Using where" since we
have restored the select pointer after doing the filesort operation.
sql/sql_select.cc:
Change create_sort_index() so that it always sets the pointer to
the select object to NULL. This is done in order to avoid that the
select->quick object can be used when execution the main part of
the select operation.
sql/sql_select.h:
New member in JOIN_TAB: saved_select. Used by create_sort_index to
make a backup copy of the select pointer.
The bug could lead to a wrong estimate of the number of expected rows
in the output of the EXPLAIN commands for queries with GROUP BY.
This could be observed in the test case for LP bug 934348.
KILL now breaks locks inside InnoDB
Fixed possible deadlock when running INNODB STATUS
Added ha_kill_query() and kill_query() to send kill signal to all storage engines
Added reset_killed() to ensure we don't reset killed state while awake() is getting called
include/mysql/plugin.h:
Added thd_mark_as_hard_kill()
include/mysql/plugin_audit.h.pp:
Added thd_mark_as_hard_kill()
include/mysql/plugin_auth.h.pp:
Added thd_mark_as_hard_kill()
include/mysql/plugin_ftparser.h.pp:
Added thd_mark_as_hard_kill()
sql/handler.cc:
Added ha_kill_query() to send kill signal to all storage engines
sql/handler.h:
Added ha_kill_query() and kill_query() to send kill signal to all storage engines
sql/log_event.cc:
Use reset_killed()
sql/mdl.cc:
use thd->killed instead of thd_killed() to abort on soft kill
sql/sp_rcontext.cc:
Use reset_killed()
sql/sql_class.cc:
Fixed possible deadlock in INNODB STATUS by not getting thd->LOCK_thd_data if it's locked.
Use reset_killed()
Tell storge engines that KILL has been sent
sql/sql_class.h:
Added reset_killed() to ensure we don't reset killed state while awake() is getting called.
Added mark_as_hard_kill()
sql/sql_insert.cc:
Use reset_killed()
sql/sql_parse.cc:
Simplify detection of killed queries.
Use reset_killed()
sql/sql_select.cc:
Use reset_killed()
sql/sql_union.cc:
Use reset_killed()
storage/innobase/handler/ha_innodb.cc:
Added innobase_kill_query()
Fixed error reporting for interrupted queries.
storage/xtradb/handler/ha_innodb.cc:
Added innobase_kill_query()
Fixed error reporting for interrupted queries.
The problem is a shift operation that is not 64-bit safe.
The consequence is that used tables information for a join with 32 tables
or more will be incorrect.
Fixed by adding a type cast in Item_sum::update_used_tables().
Also used the opportunity to fix some other potential bugs by adding an
explicit type-cast to an integer in a left-shift operation.
Some of them were quite harmless, but was fixed in order to get the same
signed-ness as the other operand of the operation it was used in.
sql/item_cmpfunc.cc
Adjusted signed-ness for some integers in left-shift.
sql/item_subselect.cc
Added type-cast to nesting_map (which is a 32/64 bit type, so
potential bug for deeply nested queries).
sql/item_sum.cc
Added type-cast to nesting_map (32/64-bit type) and table_map
(64-bit type).
sql/opt_range.cc
Added type-cast to ulonglong (which is a 64-bit type).
sql/sql_base.cc
Added type-cast to nesting_map (which is a 32/64-bit type).
sql/sql_select.cc
Added type-cast to nesting_map (32/64-bit type) and key_part_map
(64-bit type).
sql/strfunc.cc
Changed type-cast from longlong to ulonglong, to preserve signed-ness.
Analysys:
In the beginning of JOIN::cleanup there is code that is supposed to
free all filesort buffers. The code assumes that the table being sorted
is the first non-constant table. To get this table it calls:
first_top_level_tab(this, WITHOUT_CONST_TABLES)
However, first_top_level_tab() instead returned the wrong table - the first
one in the plan, instead of the first non-constant table. There is no other
place outside filesort() where sort buffers may be freed. As a result, the
sort buffer was not freed, and there was a memory leak.
Solution:
Change first_top_level_tab(), to test for WITH_CONST_TABLES instead of
WITHOUT_CONST_TABLES.
The problem was that in debugging binaries it try to print item to assign human readable name to the item.
But subquery item was already freed (join_free/cleanup with full cleanup) so Item_field refers to temporary
table which memory had been already freed.
If the setting of system variables does not allow to use join buffer
for a join query with GROUP BY <f1,...> / ORDER BY <f1,...> then
filesort is not needed if the first joined table is scanned in
the order compatible with order specified by the list <f1,...>.
MDEV-567: Wrong result from a query with correlated subquery if ICP is allowed:
backport the fix developed for SHOW EXPLAIN:
revision-id: psergey@askmonty.org-20120719115219-212cxmm6qvf0wlrb
branch nick: 5.5-show-explain-r21
timestamp: Thu 2012-07-19 15:52:19 +0400
BUG#992942 & MDEV-325: Pre-liminary commit for testing
and adjust it so that it handles DS-MRR scans correctly.
If, when executing a query with ORDER BY col LIMIT n, the optimizer chose
an index-merge scan to access the table containing col while there existed
an index defined over col then optimizer did not consider the possibility
of using an alternative range scan by this index to avoid filesort. This
could cause a performance degradation if the optimizer flag index_merge was
set up to 'on'.
Problem:-
When we execute a query which has subquery with GROUP BY, ORDER BY and have a
BLOB column,results a memory leak.
Analysis:-
In case of subquery, which have GROUP BY on BLOB and a ORDER BY on other field
and BLOB is not a key. We allocate a tmp buffer to copy_field to take care of
BLOB value.This copy_field value can have copies of its in two join(objects),
so while freeing this copy_field we have to take care that it is
not deleted twice.
The double deletion of tmp_table_param.copy_field is handled by two patches.
One by Kostja :
revid:sp1r-konstantin@mysql.com-20050627101056-55153
Fix the broken test suite in -debug build.
and other by Oleksandr
revid:sp1r-bell@sanja.is.com.ua-20060118114857-19905
Excluded posibility of tmp_table_param.copy_field double deletion (BUG#14851).
both of this patches are commited in different branch and while
merging they both get placed,but there is no need for Kostja patch as Oleksandr
patch handle this.
sql/sql_select.cc:
Bug13726751, tmp_join clean up is not necessary as later in the code we are taking care of cleaning up of tmp_join copy_field.
Problem:-
When we execute a query which has subquery with GROUP BY, ORDER BY and have a
BLOB column,results a memory leak.
Analysis:-
In case of subquery, which have GROUP BY on BLOB and a ORDER BY on other field
and BLOB is not a key. We allocate a tmp buffer to copy_field to take care of
BLOB value.This copy_field value can have copies of its in two join(objects),
so while freeing this copy_field we have to take care that it is
not deleted twice.
The double deletion of tmp_table_param.copy_field is handled by two patches.
One by Kostja :
revid:sp1r-konstantin@mysql.com-20050627101056-55153
Fix the broken test suite in -debug build.
and other by Oleksandr
revid:sp1r-bell@sanja.is.com.ua-20060118114857-19905
Excluded posibility of tmp_table_param.copy_field double deletion (BUG#14851).
both of this patches are commited in different branch and while
merging they both get placed,but there is no need for Kostja patch as Oleksandr
patch handle this.
sql/sql_select.cc:
Bug13726751, tmp_join clean up is not necessary as later in the code we are taking care of cleaning up of tmp_join copy_field.
Fix by Sergey Petrunia.
This patch only prevents the evaluation of expensive subqueries during optimization.
The crash reported in this bug has been fixed by some other patch.
The fix is to call value->is_null() only when !value->is_expensive(), because is_null()
may trigger evaluation of the Item, which in turn triggers subquery evaluation if the
Item is a subquery.
.. into MariaDB 5.3
Fix for Bug#12667154 SAME QUERY EXEC AS WHERE SUBQ GIVES DIFFERENT
RESULTS ON IN() & NOT IN() COMP #3
This bug causes a wrong result in mysql-trunk when ICP is used
and bad performance in mysql-5.5 and mysql-trunk.
Using the query from bug report to explain what happens and causes
the wrong result from the query when ICP is enabled:
1. The t3 table contains four records. The outer query will read
these and for each of these it will execute the subquery.
2. Before the first execution of the subquery it will be optimized. In
this case the important is what happens to the first table t1:
-make_join_select() will call the range optimizer which decides
that t1 should be accessed using a range scan on the k1 index
It creates a QUICK_RANGE_SELECT object for this.
-As the last part of optimization the ICP code pushes the
condition down to the storage engine for table t1 on the k1 index.
This produces the following information in the explain for this table:
2 DEPENDENT SUBQUERY t1 range k1 k1 5 NULL 3 Using index condition; Using filesort
Note the use of filesort.
3. The first execution of the subquery does (among other things) due
to the need for sorting:
a. Call create_sort_index() which again will call find_all_keys():
b. find_all_keys() will read the required keys for all qualifying
rows from the storage engine. To do this it checks if it has a
quick-select for the table. It will use the quick-select for
reading records. In this case it will read four records from the
storage engine (based on the range criteria). The storage engine
will evaluate the pushed index condition for each record.
c. At the end of create_sort_index() there is code that cleans up a
lot of stuff on the join tab. One of the things that is cleaned
is the select object. The result of this is that the
quick-select object created in make_join_select is deleted.
4. The second execution of the subquery does the same as the first but
the result is different:
a. Call create_sort_index() which again will call find_all_keys()
(same as for the first execution)
b. find_all_keys() will read the keys from the storage engine. To
do this it checks if it has a quick-select for the table. Now
there is NO quick-select object(!) (since it was deleted in
step 3c). So find_all_keys defaults to read the table using a
table scan instead. So instead of reading the four relevant records
in the range it reads the entire table (6 records). It then
evaluates the table's condition (and here it goes wrong). Since
the entire condition has been pushed down to the storage engine
using ICP all 6 records qualify. (Note that the storage engine
will not evaluate the pushed index condition in this case since
it was pushed for the k1 index and now we do a table scan
without any index being used).
The result is that here we return six qualifying key values
instead of four due to not evaluating the table's condition.
c. As above.
5. The two last execution of the subquery will also produce wrong results
for the same reason.
Summary: The problem occurs due to all but the first executions of the
subquery is done as a table scan without evaluating the table's
condition (which is pushed to the storage engine on a different
index). This is caused by the create_sort_index() function deleting
the quick-select object that should have been used for executing the
subquery as a range scan.
Note that this bug in addition to causing wrong results also can
result in bad performance due to executing the subquery using a table
scan instead of a range scan. This is an issue in MySQL 5.5.
The fix for this problem is to avoid that the Quick-select-object that
the optimizer created is deleted when create_sort_index() is doing
clean-up of the join-tab. This will ensure that the quick-select
object and the corresponding pushed index condition will be available
and used by all following executions of the subquery.
CONSISTENT SNAPSHOT OPTION
A transaction is started with a consistent snapshot. After
the transaction is started new indexes are added to the
table. Now when we issue an update statement, the optimizer
chooses an index. When the index scan is being initialized
via ha_innobase::change_active_index(), InnoDB reports
the error code HA_ERR_TABLE_DEF_CHANGED, with message
stating that "insufficient history for index".
This error message is propagated up to the SQL layer. But
the my_error() api is never called. The statement level
diagnostics area is not updated with the correct error
status (it remains in Diagnostics_area::DA_EMPTY).
Hence the following check in the Protocol::end_statement()
fails.
516 case Diagnostics_area::DA_EMPTY:
517 default:
518 DBUG_ASSERT(0);
519 error= send_ok(thd->server_status, 0, 0, 0, NULL);
520 break;
The fix is to backport the fix of bugs 14365043, 11761652
and 11746399.
14365043 PROTOCOL::END_STATEMENT(): ASSERTION `0' FAILED
11761652 HA_RND_INIT() RESULT CODE NOT CHECKED
11746399 RETURN VALUES OF HA_INDEX_INIT() AND INDEX_INIT() IGNORED
rb://1227 approved by guilhem and mattiasj.
Bug#14530242 CRASH / MEMORY CORRUPTION IN FILESORT_BUFFER::GET_RECORD_BUFFER WITH MYISAM
This is a backport of
Bug#12694872 - VALGRIND: 18,816 BYTES IN 196 BLOCKS ARE DEFINITELY LOST
Bug#13340270: assertion table->sort.record_pointers == __null
Bug#14536113 CRASH IN CLOSEFRM (TABLE.CC) OR UNPACK (FIELD.H) ON SUBQUERY WITH MYISAM TABLES
Also:
removed and re-added test files with file-ids from trunk.
The problem was that was_null and null_value variables was reset in each reexecution of IN subquery, but engine rerun only for non-constant subqueries.
Fixed checking constant in Item_equal sort.
Fix constant reporting in Item_subselect.
Documentation for class Item_outer_ref was wrong:
(*ref) may point to Item_field as well
(see e.g. Item_outer_ref::fix_fields)
So this casting in get_store_key() was wrong:
(*(Item_ref**)((Item_ref*)keyuse->val)->ref)->ref_type()
two tests still fail:
main.innodb_icp and main.range_vs_index_merge_innodb
call records_in_range() with both range ends being open
(which triggers an assert)
The fix backports from MWL#182: Explain running statements the logic that
saves the original JOIN_TAB array of a query plan after optimization. This
array is later used during EXPLAIN to iterate over the original JOIN plan
nodes in the cases when this plan could be changed by early subquery
execution during the optimization phase of the outer query.
sql/item_subselect.cc:
Added purecov info
sql/sql_select.cc:
Added cast
storage/innobase/handler/ha_innodb.cc:
Added cast
storage/xtradb/btr/btr0btr.c:
Added buf_block_get_frame_fast() to avoid compiler warning
storage/xtradb/handler/ha_innodb.cc:
Added cast
storage/xtradb/include/buf0buf.h:
Innodb has buf_block_get_frame(block) defined as (block)->frame.
Didn't want to do a big change to break xtradb as it may use block_get_frame() differently, so I mad this quick hack to patch one compiler warning.
