--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.
create_sort_index() function overwrites original JOIN_TAB::type field.
At re-execution of subquery overwritten JOIN_TAB::type(JT_ALL) is
used instead of JT_FT. It misleads test_if_skip_sort_order() and
the function tries to find suitable key for the order that should
not be allowed for FULLTEXT(JT_FT) table.
The fix is to restore JOIN_TAB strucures for subselect on re-execution
for EXPLAIN.
Additional fix:
Update TABLE::maybe_null field which
affects list_contains_unique_index() behaviour as it
could have the value(maybe_null==TRUE) based on the
assumption that this join is outer
(see setup_table_map() func).
The crash happens because original join table is replaced with temporary table
at execution stage and later we attempt to use this temporary table in
select_describe. It might happen that
Item_subselect::update_used_tables() method which sets const_item flag
is not called by some reasons (no where/having conditon in subquery for example).
It prevents JOIN::join_tmp creation and breaks original join.
The fix is to call ::update_used_tables() before ::const_item() check.
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.
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.
strict aliasing violations.
One somewhat major source of strict-aliasing violations and
related warnings is the SQL_LIST structure. For example,
consider its member function `link_in_list` which takes
a pointer to pointer of type T (any type) as a pointer to
pointer to unsigned char. Dereferencing this pointer, which
is done to reset the next field, violates strict-aliasing
rules and might cause problems for surrounding code that
uses the next field of the object being added to the list.
The solution is to use templates to parametrize the SQL_LIST
structure in order to deference the pointers with compatible
types. As a side bonus, it becomes possible to remove quite
a few casts related to acessing data members of SQL_LIST.
We should disable const subselect item evaluation because
subselect transformation does not happen in view_prepare_mode
and thus val_...() methods can not be called.
This patch:
- Moves all definitions from the mysql_priv.h file into
header files for the component where the variable is
defined
- Creates header files if the component lacks one
- Eliminates all include directives from mysql_priv.h
- Eliminates all circular include cycles
- Rename time.cc to sql_time.cc
- Rename mysql_priv.h to sql_priv.h
Conflicts:
Text conflict in client/mysqlbinlog.cc
Text conflict in mysql-test/Makefile.am
Text conflict in mysql-test/collections/default.daily
Text conflict in mysql-test/r/mysqlbinlog_row_innodb.result
Text conflict in mysql-test/suite/rpl/r/rpl_typeconv_innodb.result
Text conflict in mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test
Text conflict in mysql-test/suite/rpl/t/rpl_row_create_table.test
Text conflict in mysql-test/suite/rpl/t/rpl_slave_skip.test
Text conflict in mysql-test/suite/rpl/t/rpl_typeconv_innodb.test
Text conflict in mysys/charset.c
Text conflict in sql/field.cc
Text conflict in sql/field.h
Text conflict in sql/item.h
Text conflict in sql/item_func.cc
Text conflict in sql/log.cc
Text conflict in sql/log_event.cc
Text conflict in sql/log_event_old.cc
Text conflict in sql/mysqld.cc
Text conflict in sql/rpl_utility.cc
Text conflict in sql/rpl_utility.h
Text conflict in sql/set_var.cc
Text conflict in sql/share/Makefile.am
Text conflict in sql/sql_delete.cc
Text conflict in sql/sql_plugin.cc
Text conflict in sql/sql_select.cc
Text conflict in sql/sql_table.cc
Text conflict in storage/example/ha_example.h
Text conflict in storage/federated/ha_federated.cc
Text conflict in storage/myisammrg/ha_myisammrg.cc
Text conflict in storage/myisammrg/myrg_open.c
Conflicts:
Text conflict in mysql-test/r/partition_innodb.result
Text conflict in sql/field.h
Text conflict in sql/item.h
Text conflict in sql/item_cmpfunc.h
Text conflict in sql/item_sum.h
Text conflict in sql/log_event_old.cc
Text conflict in sql/protocol.cc
Text conflict in sql/sql_select.cc
Text conflict in sql/sql_yacc.yy
The problem was that killing a query during the optimization
phase of a subselect would lead to crashes. The root of the
problem is that the subselect execution engine ignores failures
(eg: killed) during the optimization phase (JOIN::optimize),
leading to a crash once the subquery is executed due to
partially initialized structures (in this case a join tab).
The optimal solution would be to cleanup certain optimizer
structures if the optimization phase fails, but currently
there is no infrastructure to properly to track and cleanup
the structures. To workaround the whole problem one somewhat
good solution is to avoid executing a subselect if the query
has been killed. Cutting short any problems caused by failures
during the optimization phase.
------------------------------------------------------------
revno: 2597.4.17
revision-id: sp1r-davi@mysql.com/endora.local-20080328174753-24337
parent: sp1r-anozdrin/alik@quad.opbmk-20080328140038-16479
committer: davi@mysql.com/endora.local
timestamp: Fri 2008-03-28 14:47:53 -0300
message:
Bug#15192 "fatal errors" are caught by handlers in stored procedures
The problem is that fatal errors (e.g.: out of memory) were being
caught by stored procedure exception handlers which could cause
the execution to not be stopped due to a continue handler.
The solution is to not call any exception handler if the error is
fatal and send the fatal error to the client.
When values of different types are compared they're converted to a type that
allows correct comparison. This conversion is done for each comparison and
takes some time. When a constant is being compared it's possible to cache the
value after conversion to speedup comparison. In some cases (large dataset,
complex WHERE condition with many type conversions) query might be executed
7% faster.
A test case isn't provided because all changes are internal and isn't visible
outside.
The behavior of the Item_cache is changed to cache values on the first request
of cached value rather than at the moment of storing item to be cached.
A flag named value_cached is added to the Item_cache class. It's set to TRUE
when cache holds the value of the last stored item.
Function named cache_value() is added to the Item_cache class and derived classes.
This function actually caches the value of the saved item.
Item_cache_xxx::store functions now only store item to be cached and set
value_cached flag to FALSE.
Item_cache_xxx::val_xxx functions are changed to call cache_value function
prior to returning cached value if value_cached is FALSE.
The Arg_comparator::set_cmp_func function now calls cache_converted_constant
to cache constants if they need a type conversion.
The Item_cache::get_cache function is overloaded to allow setting of the
cache type.
The cache_converted_constant function is added to the Arg_comparator class.
It checks whether a value can and should be cached and if so caches it.
Bug#41756 "Strange error messages about locks from InnoDB".
In JT_EQ_REF (join_read_key()) access method,
don't try to unlock rows in the handler, unless certain that
a) they were locked
b) they are not used.
Unlocking of rows is done by the logic of the nested join loop,
and is unaware of the possible caching that the access method may
have. This could lead to double unlocking, when a row
was unlocked first after reading into the cache, and then
when taken from cache, as well as to unlocking of rows which
were actually used (but taken from cache).
Delegate part of the unlocking logic to the access method,
and in JT_EQ_REF count how many times a record was actually
used in the join. Unlock it only if it's usage count is 0.
Implemented review comments.
Bug#41756 "Strange error messages about locks from InnoDB".
In JT_EQ_REF (join_read_key()) access method,
don't try to unlock rows in the handler, unless certain that
a) they were locked
b) they are not used.
Unlocking of rows is done by the logic of the nested join loop,
and is unaware of the possible caching that the access method may
have. This could lead to double unlocking, when a row
was unlocked first after reading into the cache, and then
when taken from cache, as well as to unlocking of rows which
were actually used (but taken from cache).
Delegate part of the unlocking logic to the access method,
and in JT_EQ_REF count how many times a record was actually
used in the join. Unlock it only if it's usage count is 0.
Implemented review comments.
If an outer query is broken, a subquery might not even get set up.
EXPLAIN EXTENDED did not expect this and merrily tried to de-ref all
of the half-setup info.
We now catch this case and print as much as we have, as it doesn't cost us
anything (doesn't make regular execution slower).
on subquery inside a SP
Problem: repeated call of a SP containing an incorrect query with a
subselect may lead to failed ASSERT().
Fix: set proper sublelect's state in case of error occured during
subquery transformation.
In a subselect all fields from outer selects are marked as dependent on
selects they are belong to. In some cases optimizer substitutes it for an
equivalent expression. For example "a_field IN (SELECT outer_field)" is
substituted with "a_field = outer_field". As we moved the outer_field to the
upper select it's not really outer anymore. But it was left marked as outer.
If exists an index over a_field optimizer choose wrong execution plan and thus
return wrong result.
Now the Item_in_subselect::single_value_transformer function removes dependent
marking from fields when a subselect is optimized away.
with gcc 4.3.2
Compiling MySQL with gcc 4.3.2 and later produces a number of
warnings, many of which are new with the recent compiler
versions.
This bug will be resolved in more than one patch to limit the
size of changesets. This is the first patch, fixing a number
of the warnings, predominantly "suggest using parentheses
around && in ||", and empty for and while bodies.
with gcc 4.3.2
Compiling MySQL with gcc 4.3.2 and later produces a number of
warnings, many of which are new with the recent compiler
versions.
This bug will be resolved in more than one patch to limit the
size of changesets. This is the first patch, fixing a number
of the warnings, predominantly "suggest using parentheses
around && in ||", and empty for and while bodies.
When there is an error executing EXISTS predicates they return NULL as their string
or decimal value but don't set the NULL value flag.
Fixed by returning 0 (as a decimal or a string) on error exectuting the subquery.
Note that we can't return NULL as EXISTS is not supposed to return NULL.
Mixing aggregate functions and non-grouping columns is not allowed in the
ONLY_FULL_GROUP_BY mode. However in some cases the error wasn't thrown because
of insufficient check.
In order to check more thoroughly the new algorithm employs a list of outer
fields used in a sum function and a SELECT_LEX::full_group_by_flag.
Each non-outer field checked to find out whether it's aggregated or not and
the current select is marked accordingly.
All outer fields that are used under an aggregate function are added to the
Item_sum::outer_fields list and later checked by the Item_sum::check_sum_func
function.
Queries like:
SELECT ROW(1, 2) IN (SELECT t1.a, 2)
FROM t1 GROUP BY t1.a
or
SELECT ROW(1, 2) IN (SELECT t1.a, 2 FROM t2)
FROM t1 GROUP BY t1.a
lead to assertion failure in the
Item_in_subselect::row_value_transformer method in debugging
build, or to unexpected error message in release build:
ERROR 1247 (42S22): Reference '<list ref>' not supported (forward
reference in item list)
Unexpected error message and assertion failure have been
eliminated.
between 5.0 and 5.1.
The problem was that in the patch for Bug#11986 it was decided
to store original query in UTF8 encoding for the INFORMATION_SCHEMA.
This approach however turned out to be quite difficult to implement
properly. The main problem is to preserve the same IS-output after
dump/restore.
So, the fix is to rollback to the previous functionality, but also
to fix it to support multi-character-set-queries properly. The idea
is to generate INFORMATION_SCHEMA-query from the item-tree after
parsing view declaration. The IS-query should:
- be completely in UTF8;
- not contain character set introducers.
For more information, see WL4052.
