Analysis:
A query with implicit grouping is one with aggregate functions and
no GROUP BY clause. MariaDB inherits from MySQL an SQL extenstion
that allows mixing aggregate functions with non-aggregate fields.
If a query with such mixed select clause produces an empty result
set, the meaning of aggregate functions is well defined - either
NULL (MIN, MAX, etc.), or 0 (count(*)). However the non-aggregated
fields must also have some value, and the only reasonable value in
the case of empty result is NULL.
The cause of the many wrong results was that if a field is declared
as non-nullable (e.g. because it is a PK or NOT NULL), the semantic
analysis and the optimization phases treat this field as non-nullable,
and generate all related query plan elements based on this assumption.
Later during execution, these incorrectly configured/generated query
plan elements result in a wrong result because the selected fields
are not null due to the not-null assumption during optimization.
Solution:
Detect before the context analysys phase that a query uses implicit
grouping with mixed aggregates/non-aggregates, and set all fields
as nullable. The parser already walks the SELECT clause, and
already sets Item::with_sum_func for Items that reference aggreagate
functions. The patch adds a symmetric Item::with_field so that all
Items that reference an Item_field are marked during their
construction at parse time in the same way as with aggregate function
use.
- Fixed some issues with partitions and connection_string, which also fixed lp:716890 "Pre- and post-recovery crash in Aria"
- Fixed wrong assert in Aria
Now need to merge with latest xtradb before pushing
sql/ha_partition.cc:
Ensure that m_ordered_rec_buffer is not freed before close.
sql/mysqld.cc:
Changed to use opt_stack_trace instead of opt_pstack.
Removed references to pstack
sql/partition_element.h:
Ensure that connect_string is initialized
storage/maria/ma_key_recover.c:
Fixed wrong assert
with the test case added by this patch.
The bug cannot be reproduced with the same test case for the main
5.3 tree because the backported fix for bug 59696 masks the
problem that causes the crash in the mentioned test case. It's not
clear weather this fix masks this problem in all possible cases.
Anyway the patch for bug 698882 introduced some inconsistent data
structures that could contain indirect references to deleted object.
It happened when two Item_equal objects were merged and the Item_field
list of the second object was joined to such list of the first object.
This operation required adjustment of the backward pointers in
Item fields from the joined list. However the adjustment was missing
and this caused crashes in the tree for mwl#128.
Now the backward pointers are set only when Item_equal items are
completely built and are not changed anymore.
Made sure that the optimal fields are used by TABLE_REF objects
when building index access keys to joined tables.
Fixed a bug in the template function that sorts the elements of
a list using the bubble sort algorithm. The bug caused poor
performance of the function. Also added an optimization that
skips comparison with the most heavy elements that has been
already properly placed in the list.
Made the comparison of the fields belonging to the same Item_equal
more granular: fields belonging to the same table are also ordered
according to some rules.
get_year_value() contains code to convert 2-digits year to
4-digits. The fix for Bug#49910 added a check on the size of
the underlying field so that this conversion is not done for
YEAR(4) values. (Since otherwise one would convert invalid
YEAR(4) values to valid ones.)
The existing check does not work when Item_cache is used, since
it is not detected when the cache is based on a Field. The
reported change in behavior is due to Bug#58030 which added
extra cached items in min/max computations.
The elegant solution would be to implement
Item_cache::real_item() to return the underlying Item.
However, some side effects are observed (change in explain
output) that indicates that such a change is not straight-
forward, and definitely not appropriate for an MRU.
Instead, a Item_cache::field() method has been added in order
to get access to the underlying field. (This field() method
eliminates the need for Item_cache::eq_def() used in
test_if_ref(), but in order to limit the scope of this fix,
that code has been left as is.)
mysql-test/r/type_year.result:
Added test case for Bug#59211.
mysql-test/t/type_year.test:
Added test case for Bug#59211.
sql/item.h:
Added function Item_cache::field() to get access to the
underlying Field of a cached field Value.
sql/item_cmpfunc.cc:
Also check underlying fields of Item_cache, not just Item_Field,
when checking whether the value is of type YEAR(4) or not.
- Removed files specific to compiling on OS/2
- Removed files specific to SCO Unix packaging
- Removed "libmysqld/copyright", text is included in documentation
- Removed LaTeX headers for NDB Doxygen documentation
- Removed obsolete NDB files
- Removed "mkisofs" binaries
- Removed the "cvs2cl.pl" script
- Changed a few GPL texts to use "program" instead of "library"
--Bug#52157 various crashes and assertions with multi-table update, stored function
--Bug#54475 improper error handling causes cascading crashing failures in innodb/ndb
--Bug#57703 create view cause Assertion failed: 0, file .\item_subselect.cc, line 846
--Bug#57352 valgrind warnings when creating view
--Recently discovered problem when a nested materialized derived table is used
before being populated and it leads to incorrect result
We have several modes when we should disable subquery evaluation.
The reasons for disabling are different. It could be
uselessness of the evaluation as in case of 'CREATE VIEW'
or 'PREPARE stmt', or we should disable subquery evaluation
if tables are not locked yet as it happens in bug#54475, or
too early evaluation of subqueries can lead to wrong result
as it happened in Bug#19077.
Main problem is that if subquery items are treated as const
they are evaluated in ::fix_fields(), ::fix_length_and_dec()
of the parental items as a lot of these methods have
Item::val_...() calls inside.
We have to make subqueries non-const to prevent unnecessary
subquery evaluation. At the moment we have different methods
for this. Here is a list of these modes:
1. PREPARE stmt;
We use UNCACHEABLE_PREPARE flag.
It is set during parsing in sql_parse.cc, mysql_new_select() for
each SELECT_LEX object and cleared at the end of PREPARE in
sql_prepare.cc, init_stmt_after_parse(). If this flag is set
subquery becomes non-const and evaluation does not happen.
2. CREATE|ALTER VIEW, SHOW CREATE VIEW, I_S tables which
process FRM files
We use LEX::view_prepare_mode field. We set it before
view preparation and check this flag in
::fix_fields(), ::fix_length_and_dec().
Some bugs are fixed using this approach,
some are not(Bug#57352, Bug#57703). The problem here is
that we have a lot of ::fix_fields(), ::fix_length_and_dec()
where we use Item::val_...() calls for const items.
3. Derived tables with subquery = wrong result(Bug19077)
The reason of this bug is too early subquery evaluation.
It was fixed by adding Item::with_subselect field
The check of this field in appropriate places prevents
const item evaluation if the item have subquery.
The fix for Bug19077 fixes only the problem with
convert_constant_item() function and does not cover
other places(::fix_fields(), ::fix_length_and_dec() again)
where subqueries could be evaluated.
Example:
CREATE TABLE t1 (i INT, j BIGINT);
INSERT INTO t1 VALUES (1, 2), (2, 2), (3, 2);
SELECT * FROM (SELECT MIN(i) FROM t1
WHERE j = SUBSTRING('12', (SELECT * FROM (SELECT MIN(j) FROM t1) t2))) t3;
DROP TABLE t1;
4. Derived tables with subquery where subquery
is evaluated before table locking(Bug#54475, Bug#52157)
Suggested solution is following:
-Introduce new field LEX::context_analysis_only with the following
possible flags:
#define CONTEXT_ANALYSIS_ONLY_PREPARE 1
#define CONTEXT_ANALYSIS_ONLY_VIEW 2
#define CONTEXT_ANALYSIS_ONLY_DERIVED 4
-Set/clean these flags when we perform
context analysis operation
-Item_subselect::const_item() returns
result depending on LEX::context_analysis_only.
If context_analysis_only is set then we return
FALSE that means that subquery is non-const.
As all subquery types are wrapped by Item_subselect
it allow as to make subquery non-const when
it's necessary.
mysql-test/r/derived.result:
test case
mysql-test/r/multi_update.result:
test case
mysql-test/r/view.result:
test case
mysql-test/suite/innodb/r/innodb_multi_update.result:
test case
mysql-test/suite/innodb/t/innodb_multi_update.test:
test case
mysql-test/suite/innodb_plugin/r/innodb_multi_update.result:
test case
mysql-test/suite/innodb_plugin/t/innodb_multi_update.test:
test case
mysql-test/t/derived.test:
test case
mysql-test/t/multi_update.test:
test case
mysql-test/t/view.test:
test case
sql/item.cc:
--removed unnecessary code
sql/item_cmpfunc.cc:
--removed unnecessary checks
--THD::is_context_analysis_only() is replaced with LEX::is_ps_or_view_context_analysis()
sql/item_func.cc:
--refactored context analysis checks
sql/item_row.cc:
--removed unnecessary checks
sql/item_subselect.cc:
--removed unnecessary code
--added DBUG_ASSERT into Item_subselect::exec()
which asserts that subquery execution can not happen
if LEX::context_analysis_only is set, i.e. at context
analysis stage.
--Item_subselect::const_item()
Return FALSE if LEX::context_analysis_only is set.
It prevents subquery evaluation in ::fix_fields &
::fix_length_and_dec at context analysis stage.
sql/item_subselect.h:
--removed unnecessary code
sql/mysql_priv.h:
--Added new set of flags.
sql/sql_class.h:
--removed unnecessary code
sql/sql_derived.cc:
--added LEX::context_analysis_only analysis intialization/cleanup
sql/sql_lex.cc:
--init LEX::context_analysis_only field
sql/sql_lex.h:
--New LEX::context_analysis_only field
sql/sql_parse.cc:
--removed unnecessary code
sql/sql_prepare.cc:
--removed unnecessary code
--added LEX::context_analysis_only analysis intialization/cleanup
sql/sql_select.cc:
--refactored context analysis checks
sql/sql_show.cc:
--added LEX::context_analysis_only analysis intialization/cleanup
sql/sql_view.cc:
--added LEX::context_analysis_only analysis intialization/cleanup
Fixed compiler warning
mysql-test/r/named_pipe.result:
Fixed test results for windows builds
mysql-test/r/shm.result:
Fixed test results for windows builds
sql/item_cmpfunc.cc:
Fixed compiler warning about uninitialized "first"
- Fixed problem with oqgraph and 'make dist'
Note that after this merge we have a problem show in join_outer where we examine too many rows in one specific case (related to BUG#57024).
This will be fixed when mwl#128 is merged into 5.3.
ESCAPE argument might be empty string. It leads
to server crash under some circumstances.
The fix:
-added check if ESCAPE argument result is not empty string
mysql-test/r/ctype_latin1.result:
test case
mysql-test/t/ctype_latin1.test:
test case
sql/item_cmpfunc.cc:
-added check if ESCAPE argument result is not empty string
sql/field.cc:
Remove feature of 'new_mode' that was never implemtented in a newer MySQL version.
sql/item_cmpfunc.cc:
Boyer more is stable; Don't have to be protected by --skip-new anymore
sql/mysqld.cc:
Don't disable some proven stable functions with --skip-new
sql/records.cc:
Don't disable record caching with --safe-mode anymore
sql/sql_delete.cc:
Do fast truncate even if --skip-new or --safe is used
sql/sql_parse.cc:
Use always mysql_optimizer() for optimizer (instead of mysql_recreate_table() in case of --safe or --skip-new)
sql/sql_select.cc:
Don't disable 'only_eq_ref_tables' if --safe is used.
sql/sql_yacc.yy:
Removed not meaningfull test of --old
The problem could be demonstrated with an outer join of two single-row
tables where the values of the join attributes were null. Any query
with such a join could return a wrong result set if the where
condition of the query was not empty. For queries with empty
where conditions the result sets were correct.
This was the consequence of two bugs in the code:
- Item_equal objects for on conditions of outer joins were
not built if the processed query had no where condition
- the check for null values in the code that evaluated constant
Item_equal objects was incorrect.
Fixed both above problems.
Added a test case for the bug and adjusted results for some other
test cases.
result
Row subqueries producing no rows were not handled as UNKNOWN
values in row comparison expressions.
That was a result of the following two problems:
1. Item_singlerow_subselect did not mark the resulting row
value as NULL/UNKNOWN when no rows were produced.
2. Arg_comparator::compare_row() did not take into account that
a whole argument may be NULL rather than just individual scalar
values.
Before bug#34384 was fixed, the above problems were hidden
because an uninitialized (i.e. without any stored value) cached
object would appear as NULL for scalar values in a row subquery
returning an empty result. After the fix
Arg_comparator::compare_row() would try to evaluate
uninitialized cached objects.
Fixed by removing the aforementioned problems.
mysql-test/r/row.result:
Added a test case for bug #54190.
mysql-test/r/subselect.result:
Updated the result for a test relying on wrong behavior.
mysql-test/t/row.test:
Added a test case for bug #54190.
sql/item_cmpfunc.cc:
If either of the argument rows is NULL, return NULL as the
result of comparison.
sql/item_subselect.cc:
Adjust null_value for Item_singlerow_subselect depending on
whether a row has been produced by the row subquery.
The EXISTS transformation has additional switches to catch the known corner
cases that appear when transforming an IN predicate into EXISTS. Guarded
conditions are used which are deactivated when a NULL value is seen in the
outer expression's row. When the inner query block supplies NULL values,
however, they are filtered out because no distinction is made between the
guarded conditions; guarded NOT x IS NULL conditions in the HAVING clause that
filter out NULL values cannot be de-activated in isolation from those that
match values or from the outer expression or NULL's.
The above problem is handled by making the guarded conditions remember whether
they have rejected a NULL value or not, and index access methods are taking
this into account as well.
The bug consisted of
1) Not resetting the property for every nested loop iteration on the inner
query's result.
2) Not propagating the NULL result properly from inner query to IN optimizer.
3) A hack that may or may not have been needed at some point. According to a
comment it was aimed to fix#2 by returning NULL when FALSE was actually
the result. This caused failures when #2 was properly fixed. The hack is
now removed.
The fix resolves all three points.
file .\item_subselect.cc, line 836
IN quantified predicates are never executed directly. They are rather wrapped
inside nodes called IN Optimizers (Item_in_optimizer) which take care of the
execution. However, this is not done during query preparation. Unfortunately
the LIKE predicate pre-evaluates constant right-hand side arguments even
during name resolution. Likely this is meant as an optimization.
Fixed by not pre-evaluating LIKE arguments in view prepare mode.
If the expression for a virtual column of table contained datetime
comparison then the execution of the second query that used this
virtual column caused a crash. It happened because the execution
of the first query that used this virtual column inserted a cached
item into the expression tree. The cached tree was allocated in
the statement memory while the expression tree was allocated in
the table memory.
Now the cached items that are inserted into expressions for virtual
columns with datetime comparisons are always allocated in the same
mem_root as the expressions for virtual columns. So now the inserted
cached items are valid for any queries that use these virtual columns.
Fixed compiler warnings.
queues.h and queues.c are now based on the UNIREG code and thus made BSD.
Fix code to use new queue() interface. This mostly affects how you access elements in the queue.
If USE_NET_CLEAR is not set, don't clear connection from unexpected characters. This should give a speed up when doing a lot of fast queries.
Fixed some code in ma_ft_boolean_search.c that had not made it from myisam/ft_boolean_search.c
include/queues.h:
Use UNIREG code base (BSD)
Changed init_queue() to take all initialization arguments.
New interface to access elements in queue
include/thr_alarm.h:
Changed to use time_t instead of ulong (portability)
Added index_in_queue, to be able to remove random element from queue in O(1)
mysys/queues.c:
Use UNIREG code base (BSD)
init_queue() and reinit_queue() now takes more initialization arguments. (No need for init_queue_ex() anymore)
Now one can tell queue_insert() to store in the element a pointer to where element is in queue. This allows one to remove elements from queue in O(1) instead of O(N)
mysys/thr_alarm.c:
Use new option in queue() to allow fast removal of elements.
Do less inside LOCK_alarm mutex.
This should give a major speed up of thr_alarm usage when there is many threads
sql/create_options.cc:
Fixed wrong printf
sql/event_queue.cc:
Use new queue interface()
sql/filesort.cc:
Use new queue interface()
sql/ha_partition.cc:
Use new queue interface()
sql/ha_partition.h:
Fixed compiler warning
sql/item_cmpfunc.cc:
Fixed compiler warning
sql/item_subselect.cc:
Use new queue interface()
Removed not used variable
sql/net_serv.cc:
If USE_NET_CLEAR is not set, don't clear connection from unexpected characters.
This should give a speed up when doing a lot of fast queries at the disadvantage that if there is a bug in the client protocol the connection will be dropped instead of being unnoticed.
sql/opt_range.cc:
Use new queue interface()
Fixed compiler warnings
sql/uniques.cc:
Use new queue interface()
storage/maria/ma_ft_boolean_search.c:
Copy code from myisam/ft_boolean_search.c
Use new queue interface()
storage/maria/ma_ft_nlq_search.c:
Use new queue interface()
storage/maria/ma_sort.c:
Use new queue interface()
storage/maria/maria_pack.c:
Use new queue interface()
Use queue_fix() instead of own loop to fix queue.
storage/myisam/ft_boolean_search.c:
Use new queue interface()
storage/myisam/ft_nlq_search.c:
Use new queue interface()
storage/myisam/mi_test_all.sh:
Remove temporary file from last run
storage/myisam/myisampack.c:
Use new queue interface()
Use queue_fix() instead of own loop to fix queue.
storage/myisam/sort.c:
Use new queue interface()
storage/myisammrg/myrg_queue.c:
Use new queue interface()
storage/myisammrg/myrg_rnext.c:
Use new queue interface()
storage/myisammrg/myrg_rnext_same.c:
Use new queue interface()
storage/myisammrg/myrg_rprev.c:
Use new queue interface()
libmysqld/Makefile.am:
The new file added.
mysql-test/r/index_merge_myisam.result:
subquery_cache optimization option added.
mysql-test/r/myisam_mrr.result:
subquery_cache optimization option added.
mysql-test/r/subquery_cache.result:
The subquery cache tests added.
mysql-test/r/subselect3.result:
Subquery cache switched off to avoid changing read statistics.
mysql-test/r/subselect3_jcl6.result:
Subquery cache switched off to avoid changing read statistics.
mysql-test/r/subselect_no_mat.result:
subquery_cache optimization option added.
mysql-test/r/subselect_no_opts.result:
subquery_cache optimization option added.
mysql-test/r/subselect_no_semijoin.result:
subquery_cache optimization option added.
mysql-test/r/subselect_sj.result:
subquery_cache optimization option added.
mysql-test/r/subselect_sj_jcl6.result:
subquery_cache optimization option added.
mysql-test/t/subquery_cache.test:
The subquery cache tests added.
mysql-test/t/subselect3.test:
Subquery cache switched off to avoid changing read statistics.
sql/CMakeLists.txt:
The new file added.
sql/Makefile.am:
The new files added.
sql/item.cc:
Expression cache item (Item_cache_wrapper) added.
Item_ref and Item_field fixed for correct usage of result field and fast resolwing in SP.
sql/item.h:
Expression cache item (Item_cache_wrapper) added.
Item_ref and Item_field fixed for correct usage of result field and fast resolwing in SP.
sql/item_cmpfunc.cc:
Subquery cache added.
sql/item_cmpfunc.h:
Subquery cache added.
sql/item_subselect.cc:
Subquery cache added.
sql/item_subselect.h:
Subquery cache added.
sql/item_sum.cc:
Registration of subquery parameters added.
sql/mysql_priv.h:
subquery_cache optimization option added.
sql/mysqld.cc:
subquery_cache optimization option added.
sql/opt_range.cc:
Fix due to subquery cache.
sql/opt_subselect.cc:
Parameters of the function cahnged.
sql/procedure.h:
.h file guard added.
sql/sql_base.cc:
Registration of subquery parameters added.
sql/sql_class.cc:
Option to allow add indeces to temporary table.
sql/sql_class.h:
Item iterators added.
Option to allow add indeces to temporary table.
sql/sql_expression_cache.cc:
Expression cache for caching subqueries added.
sql/sql_expression_cache.h:
Expression cache for caching subqueries added.
sql/sql_lex.cc:
Registration of subquery parameters added.
sql/sql_lex.h:
Registration of subqueries and subquery parameters added.
sql/sql_select.cc:
Subquery cache added.
sql/sql_select.h:
Subquery cache added.
sql/sql_union.cc:
A new parameter to the function added.
sql/sql_update.cc:
A new parameter to the function added.
sql/table.cc:
Procedures to manage temporarty tables index added.
sql/table.h:
Procedures to manage temporarty tables index added.
storage/maria/ha_maria.cc:
Fix of handler to allow destoy a table in case of error during the table creation.
storage/maria/ha_maria.h:
.h file guard added.
storage/myisam/ha_myisam.cc:
Fix of handler to allow destoy a table in case of error during the table creation.
Incorrect handling of NULL arguments could lead to a crash on
the IN or CASE operations when either NULL arguments were
passed explicitly as arguments (IN) or implicitly generated by
the WITH ROLLUP modifier (both IN and CASE).
Item_func_case::find_item() assumed all necessary comparators
to be instantiated in fix_length_and_dec(). However, in the
presence of WITH ROLLUP modifier, arguments could be
substituted with an Item_null leading to an "unexpected"
STRING_RESULT comparator being invoked.
In addition to the problem identical to the above,
Item_func_in::val_int() could crash even with explicitly passed
NULL arguments due to an optimization in fix_length_and_dec()
leading to NULL arguments being ignored during comparators
creation.
mysql-test/r/func_in.result:
Test cases for bug#54477.
mysql-test/t/func_in.test:
Test cases for bug#54477.
sql/item_cmpfunc.cc:
Added additional checks for Item_nulls in
Item_func_case::find_item() and Item_func_in::val_int().
Problem: a flaw (derefencing a NULL pointer) in the LIKE optimization
code may lead to a server crash in some rare cases.
Fix: check the pointer before its dereferencing.
mysql-test/r/func_like.result:
Fix for bug #54575: crash when joining tables with unique set column
- test result.
mysql-test/t/func_like.test:
Fix for bug #54575: crash when joining tables with unique set column
- test case.
sql/item_cmpfunc.cc:
Fix for bug #54575: crash when joining tables with unique set column
- check res2 buffer pointer before its dereferencing
as it may be NULL in some cases.
