Analysis:
The crash is a result of Item_cache_temporal::example not being set
(it is NULL). It turns out that the value of Item_cache_temporal
may be set directly by calling Item_cache_temporal::store_packed
without ever setting the "example" of this Item_cache. Therefore
the failing assertion is too narrow.
Solution:
Remove the assert.
In principle we could overwrite this method for Item_cache_temporal,
but it doesn't make sense just for this assert.
The patch enables back constant subquery execution during
query optimization after it was disabled during the development
of MWL#89 (cost-based choice of IN-TO-EXISTS vs MATERIALIZATION).
The main idea is that constant subqueries are allowed to be executed
during optimization if their execution is not expensive.
The approach is as follows:
- Constant subqueries are recursively optimized in the beginning of
JOIN::optimize of the outer query. This is done by the new method
JOIN::optimize_constant_subqueries(). This is done so that the cost
of executing these queries can be estimated.
- Optimization of the outer query proceeds normally. During this phase
the optimizer may request execution of non-expensive constant subqueries.
Each place where the optimizer may potentially execute an expensive
expression is guarded with the predicate Item::is_expensive().
- The implementation of Item_subselect::is_expensive has been extended
to use the number of examined rows (estimated by the optimizer) as a
way to determine whether the subquery is expensive or not.
- The new system variable "expensive_subquery_limit" controls how many
examined rows are considered to be not expensive. The default is 100.
In addition, multiple changes were needed to make this solution work
in the light of the changes made by MWL#89. These changes were needed
to fix various crashes and wrong results, and legacy bugs discovered
during development.
This bug happened because the function find_field_in_view formed
autogenerated names of view columns without a possibility to roll
them back. In some situation it could cause memory misuses reported
by valgrind or even crashes.
Analysis:
========================
sql_mode "NO_BACKSLASH_ESCAPES": When user want to use backslash as character input,
instead of escape character in a string literal then sql_mode can be set to
"NO_BACKSLASH_ESCAPES". With this mode enabled, backslash becomes an ordinary
character like any other.
SQL_MODE set applies to the current client session. And while creating the stored
procedure, MySQL stores the current sql_mode and always executes the stored
procedure in sql_mode stored with the Procedure, regardless of the server SQL
mode in effect when the routine is invoked.
In the scenario (for which bug is reported), the routine is created with
sql_mode=NO_BACKSLASH_ESCAPES. And routine is executed with the invoker sql_mode
is "" (NOT SET) by executing statement "call testp('Axel\'s')".
Since invoker sql_mode is "" (NOT_SET), the '\' in 'Axel\'s'(argument to function)
is considered as escape character and column "a" (of table "t1") values are
updated with "Axel's". The binary log generated for above update operation is as below,
set sql_mode=XXXXXX (for no_backslash_escapes)
update test.t1 set a= NAME_CONST('var',_latin1'Axel\'s' COLLATE 'latin1_swedish_ci');
While logging stored procedure statements, the local variables (params) used in
statements are replaced with the NAME_CONST(var_name, var_value) (Internal function)
(http://dev.mysql.com/doc/refman/5.6/en/miscellaneous-functions.html#function_name-const)
On slave, these logs are applied. NAME_CONST is parsed to get the variable and its
value. Since, stored procedure is created with sql_mode="NO_BACKSLASH_ESCAPES", the sql_mode
is also logged in. So that at slave this sql_mode is set before executing the statements
of routine. So at slave, sql_mode is set to "NO_BACKSLASH_ESCAPES" and then while
parsing NAME_CONST of string variable, '\' is considered as NON ESCAPE character
and parsing reported error for "'" (as we have only one "'" no backslash).
At slave, parsing was proper with sql_mode "NO_BACKSLASH_ESCAPES".
But above error reported while writing bin log, "'" (of Axel's) is escaped with
"\" character. Actually, all special characters (n, r, ', ", \, 0...) are escaped
while writing NAME_CONST for string variable(param, local variable) in bin log
Airrespective of "NO_BACKSLASH_ESCAPES" sql_mode. So, basically, the problem is
that logging string parameter does not take into account sql_mode value.
Fix:
========================
So when sql_mode is set to "NO_BACKSLASH_ESCAPES", escaping characters as
(n, r, ', ", \, 0...) should be avoided. To do so, added a check to not to
escape such characters while writing NAME_CONST for string variables in bin
log.
And when sql_mode is set to NO_BACKSLASH_ESCAPES, quote character "'" is
represented as ''.
http://dev.mysql.com/doc/refman/5.6/en/string-literals.html (There are several
ways to include quote characters within a string: )
mysql-test/r/sql_mode.result:
Added test case for Bug#12601974.
mysql-test/suite/binlog/r/binlog_sql_mode.result:
Appended result of test cases added for Bug#12601974.
mysql-test/suite/binlog/t/binlog_sql_mode.test:
Added test case for Bug#12601974.
mysql-test/t/sql_mode.test:
Appended result of test cases added for Bug#12601974.
Analysis:
========================
sql_mode "NO_BACKSLASH_ESCAPES": When user want to use backslash as character input,
instead of escape character in a string literal then sql_mode can be set to
"NO_BACKSLASH_ESCAPES". With this mode enabled, backslash becomes an ordinary
character like any other.
SQL_MODE set applies to the current client session. And while creating the stored
procedure, MySQL stores the current sql_mode and always executes the stored
procedure in sql_mode stored with the Procedure, regardless of the server SQL
mode in effect when the routine is invoked.
In the scenario (for which bug is reported), the routine is created with
sql_mode=NO_BACKSLASH_ESCAPES. And routine is executed with the invoker sql_mode
is "" (NOT SET) by executing statement "call testp('Axel\'s')".
Since invoker sql_mode is "" (NOT_SET), the '\' in 'Axel\'s'(argument to function)
is considered as escape character and column "a" (of table "t1") values are
updated with "Axel's". The binary log generated for above update operation is as below,
set sql_mode=XXXXXX (for no_backslash_escapes)
update test.t1 set a= NAME_CONST('var',_latin1'Axel\'s' COLLATE 'latin1_swedish_ci');
While logging stored procedure statements, the local variables (params) used in
statements are replaced with the NAME_CONST(var_name, var_value) (Internal function)
(http://dev.mysql.com/doc/refman/5.6/en/miscellaneous-functions.html#function_name-const)
On slave, these logs are applied. NAME_CONST is parsed to get the variable and its
value. Since, stored procedure is created with sql_mode="NO_BACKSLASH_ESCAPES", the sql_mode
is also logged in. So that at slave this sql_mode is set before executing the statements
of routine. So at slave, sql_mode is set to "NO_BACKSLASH_ESCAPES" and then while
parsing NAME_CONST of string variable, '\' is considered as NON ESCAPE character
and parsing reported error for "'" (as we have only one "'" no backslash).
At slave, parsing was proper with sql_mode "NO_BACKSLASH_ESCAPES".
But above error reported while writing bin log, "'" (of Axel's) is escaped with
"\" character. Actually, all special characters (n, r, ', ", \, 0...) are escaped
while writing NAME_CONST for string variable(param, local variable) in bin log
Airrespective of "NO_BACKSLASH_ESCAPES" sql_mode. So, basically, the problem is
that logging string parameter does not take into account sql_mode value.
Fix:
========================
So when sql_mode is set to "NO_BACKSLASH_ESCAPES", escaping characters as
(n, r, ', ", \, 0...) should be avoided. To do so, added a check to not to
escape such characters while writing NAME_CONST for string variables in bin
log.
And when sql_mode is set to NO_BACKSLASH_ESCAPES, quote character "'" is
represented as ''.
http://dev.mysql.com/doc/refman/5.6/en/string-literals.html (There are several
ways to include quote characters within a string: )
- MySQL 5.5 introduced caching of constant items by means of
wrapping them in Item_cache_XXX objects. If a subquery was wrapped
in this cache, it could end up being pushed down by ICP.
- The fix is to add Item_cache::walk() which lets ICP to see that
the cache item has a subquery inside it, and disable pushdown for this case.
- equality substitution code was geared towards processing WHERE/ON clauses.
that is, it assumed that it was doing substitions on the code that
= wasn't attached to any particular join_tab yet
= was going to be fed to make_join_select() which would take the condition
apart and attach various parts of it to tables inside/outside semi-joins.
- However, somebody added equality substition for ref access. That is, if
we have a ref access on TBL.key=expr, they would do equality substition in
'expr'. This possibility wasn't accounted for.
- Fixed equality substition code by adding a mode that does equality
substition under assumption that the processed expression will be
attached to a certain particular table TBL.
The problem was that when we have single row subquery with no rows
Item_cache(es) which represent result row was not null and being
requested via element_index() returned random value.
The fix is setting all Item_cache(es) in NULL before executing the
query (reset() method) which guaranty NULL value of whole query
or its elements requested in any way if no rows was found.
set_null() method was added to Item_cache to guaranty correct NULL
value in case of reseting the cache.
MariaDB 5.5 merges changes from MySQL 5.5 where all constant
expressions are wrapped into an Item_cache. As a result, constant
single-row subqueries were also wrapped in an Item_cache.
When analyzing the where clause for constant expressions that
can be evaluated during optimization, subqueries wrapped into
an Item_cache did not appear as expensive, and were therefore
evaluated during optimization. Such evaluation is against the
current architecture of MariaDB 5.3 where subquries are executed
during the execute phase.
The patch adds the is_expensive() predicate to Item_cache.
This makes Item_cache consistent with other wrapping Item
classes that need to look at the properties of the wrapped
object.
The problem was that merged views has its own nest_level numbering =>
when we compare nest levels we should take into considiration basis (i.e. 0 level),
if it is different then nest levels are not comparable.
This bug happened for the queries over multi-table mergeable views
because the bitmap TABLE::read_set of the underlying tables were not
updated after the views had been merged into the query.
Now this bitmaps are updated properly.
Also the bitmap TABLE::merge_keys now is updated in prevention of
future bugs.
This bug happened due to incompleteness of the fix for bug 872735:
the occurrences of the fields in the conditions of correlated
subqueries were not taken into account when recalculating
covering keys bit maps.
sql/sql_insert.cc:
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
******
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
sql/sql_table.cc:
small cleanup
******
small cleanup
This bug happened because the maps of covering keys for mergeable derived
tables/views was not recalculated after the derived tables/vies had been
merged into the main query.
When temporary tables is used for result sorting
result field for gconcat function is created using
group_concat_max_len size. It leads to result truncation
when character_set_results is multi-byte character set due
to insufficient tmp table field size.
The fix is to increase temporary table field size for
gconcat. Method make_string_field() is overloaded
for Item_func_group_concat class and uses
max_characters * collation.collation->mbmaxlen size for
result field. max_characters is maximum number of characters
what can fit into max_length size.
mysql-test/r/ctype_utf16.result:
test result
mysql-test/r/ctype_utf32.result:
test result
mysql-test/r/ctype_utf8.result:
test result
mysql-test/t/ctype_utf16.test:
test case
mysql-test/t/ctype_utf32.test:
test case
mysql-test/t/ctype_utf8.test:
test case
sql/item.h:
make Item::make_string_field() virtual
sql/item_sum.cc:
added Item_func_group_concat::make_string_field(TABLE *table) method
which uses max_characters * collation.collation->mbmaxlen size for
result item. max_characters is maximum number of characters what can
fit into max_length size.
sql/item_sum.h:
added Item_func_group_concat::make_string_field(TABLE *table) method
When temporary tables is used for result sorting
result field for gconcat function is created using
group_concat_max_len size. It leads to result truncation
when character_set_results is multi-byte character set due
to insufficient tmp table field size.
The fix is to increase temporary table field size for
gconcat. Method make_string_field() is overloaded
for Item_func_group_concat class and uses
max_characters * collation.collation->mbmaxlen size for
result field. max_characters is maximum number of characters
what can fit into max_length size.
- The bug was caused by outer join being incorrectly converted into inner because of
invalid return values of Item_direct_view_ref::not_null_tables().
- Provided a correct Item_direct_view_ref::not_null_tables() function.
- The problem was that the code that made the check whether the subquery is an AND-part of the WHERE
clause didn't work correctly for nested subqueries. In particular, grand-child subquery in HAVING was
treated as if it was in the WHERE, which eventually caused an assert when replace_where_subcondition
looked for the subquery predicate in the WHERE and couldn't find it there.
- The fix: Removed implementation of "thd_marker approach". thd->thd_marker was used to determine the
location of subquery predicate: setup_conds() would set accordingly it when making the
{where|on_expr}->fix_fields(...)
call so that AND-parts of the WHERE/ON clauses can determine they are the AND-parts.
Item_cond_or::fix_fields(), Item_func::fix_fields(), Item_subselect::fix_fields (this one was missed),
and all other items-that-contain-items had to reset thd->thd_marker before calling fix_fields() for
their children items, so that the children can see they are not AND-parts of WHERE/ON.
- The "thd_marker approach" required that a lot of code in different locations maintains correct value of
thd->thd_marker, so it was replaced with:
- The new approach with mark_as_condition_AND_part does not keep context in thd->thd_marker. Instead,
setup_conds() now calls
{where|on_expr}->mark_as_condition_AND_part()
and implementations of that function make sure that:
- parts of AND-expressions get the mark_as_condition_AND_part() call
- Item_in_subselect objects record that they are AND-parts of WHERE/ON
SET STATEMENT.
Server built with debug asserts, without debug crashes if a user tries
to run a stored procedure that constains query with subquery that include
either LIMIT or LIMIT OFFSET clauses.
The problem was that Item::fix_fields() was not called for the items
representing LIMIT or OFFSET clauses.
The solution is to call Item::fix_fields() right before evaluation in
st_select_lex_unit::set_limit().
mysql-test/r/sp.result:
Added testcase result for bug#12621017. Updated testcase result for
bug 11918.
mysql-test/t/sp.test:
Added testcase for bug#12621017. Addressed review comments for Bug 11918
(added tests for use LIMIT at stored function).
sql/item.h:
Addressed review comments for Bug 11918.
sql/share/errmsg-utf8.txt:
Addressed review comments for Bug 11918.
sql/sp_head.cc:
Addressed review comments for Bug 11918.
sql/sql_lex.cc:
Added call fix_fields() for item just before its evaluation.
sql/sql_yacc.yy:
Addressed review comments for Bug 11918.
SET STATEMENT.
Server built with debug asserts, without debug crashes if a user tries
to run a stored procedure that constains query with subquery that include
either LIMIT or LIMIT OFFSET clauses.
The problem was that Item::fix_fields() was not called for the items
representing LIMIT or OFFSET clauses.
The solution is to call Item::fix_fields() right before evaluation in
st_select_lex_unit::set_limit().
The method Item_ref::not_null_tables() returned incorrect bitmap
for outer references to view columns. This could cause an invalid
conversion of an outer join into an inner join that could lead
to a wrong result set for a query with a correlated subquery over
an outer join whose where condition had an outer reference to a view.
An aggregating query over an empty set of a join of two tables
with a rejecting HAVING clause erroneously could return a row.
It could happen in the cases when the optimizer made a conclusion
that the aggregating set was empty.
Wrong results were produced because the server missed initial
setting for aggregation functions in the mentioned cases.
The problem was that optimizer removes some outer references (it they are
constant for example) and the list of outer items built during prepare phase is
not actual during execution phase when we need it as the cache parameters.
First solution was use pointer on pointer on outer reference Item and
initialize temporary table on demand. This solved most problem except case
when optimiser also reduce Item which contains outer references ('OR' in
this bug test suite).
The solution is to build the list of outer reference items on execution
phase (after optimization) on demand (just before temporary table creation)
by walking Item tree and finding outer references among Item_ident
(Item_field/Item_ref) and Item_sum items.
Removed depends_on list (because it is not neede any mnore for the cache, in the place where it was used it replaced with upper_refs).
Added processor (collect_outer_ref_processor) and get_cache_parameters() methods to collect outer references (or other expression parameters in future).
mysql-test/r/subselect_cache.result:
A new test added.
mysql-test/r/subselect_scache.result:
Changes in creating the cache and its paremeters order or adding arguments of aggregate function (which is a parameter also, but this has no influence on the result).
mysql-test/t/subselect_cache.test:
Added a new test.
sql/item.cc:
depends_on removed.
Added processor (collect_outer_ref_processor) and get_cache_parameters() methods to collect outer references.
Item_cache_wrapper collect parameters befor initialization of its cache.
sql/item.h:
depends_on removed.
Added processor (collect_outer_ref_processor) and get_cache_parameters() methods to collect outer references.
sql/item_cmpfunc.cc:
depends_on removed.
Added processor (collect_outer_ref_processor) to collect outer references.
sql/item_cmpfunc.h:
Added processor (collect_outer_ref_processor) to collect outer references.
sql/item_subselect.cc:
depends_on removed.
Added processor get_cache_parameters() method to collect outer references.
sql/item_subselect.h:
depends_on removed.
Added processor get_cache_parameters() method to collect outer references.
sql/item_sum.cc:
Added processor (collect_outer_ref_processor) method to collect outer references.
sql/item_sum.h:
Added processor (collect_outer_ref_processor) and get_cache_parameters() methods to collect outer references.
sql/opt_range.cc:
depends_on removed.
sql/sql_base.cc:
depends_on removed.
sql/sql_class.h:
New iterator added.
sql/sql_expression_cache.cc:
Build of list of items resolved in outer query done just before creating expression cache on the first execution of the subquery which removes influence of optimizer removing items (all optimization already done).
sql/sql_expression_cache.h:
Build of list of items resolved in outer query done just before creating expression cache on the first execution of the subquery which removes influence of optimizer removing items (all optimization already done).
sql/sql_lex.cc:
depends_on removed.
sql/sql_lex.h:
depends_on removed.
sql/sql_list.h:
Added add_unique method to add only unique elements to the list.
sql/sql_select.cc:
Support of new Item list added.
sql/sql_select.h:
Support of new Item list added.
The assert conditions in the functions Item_direct_ref_to_ident::transform
and Item_direct_ref_to_ident::compile could be not valid after constant
propagation when fields and field references may be substituted for constants.
Not only these invalid asserts have been removed, but the functions containing
them have been removed as well because now Item_ref::transform and
Item_ref::compile can be used instead of them.
COLUMNS IN VIEWS
Issue:
charset value for a Column, returned by MYSQL_LIST_FIELDS(), was not same
for Table and View. This was because, for view, field charset was not being
returned.
Solution:
Added definition of function "charset_for_protocol()" in calss
Item_ident_for_show to return field charset value.
sql/item.h:
Added definition for charset_for_protocol() function to return field charset.
tests/mysql_client_test.c:
Added a test case test_bug12337762 for the changes done.
COLUMNS IN VIEWS
Issue:
charset value for a Column, returned by MYSQL_LIST_FIELDS(), was not same
for Table and View. This was because, for view, field charset was not being
returned.
Solution:
Added definition of function "charset_for_protocol()" in calss
Item_ident_for_show to return field charset value.
microsecond(TIME)
alter table datetime<->datetime(6)
max(TIME), mix(TIME)
mysql-test/t/func_if.test:
fix the test case of avoid overflow
sql/field.cc:
don't use make_date() and make_time()
sql/field.h:
correct eq_def() for temporal fields
sql/item.cc:
move datetime caching from Item_cache_int
to Item_cache_temporal
sql/item.h:
move datetime caching from Item_cache_int
to Item_cache_temporal
sql/item_func.cc:
use existing helper methods, don't duplicate
sql/item_sum.cc:
argument cache must use argument's cmp_type, not result_type.
sql/item_timefunc.cc:
use existing methods, don't tuplicate.
remove unused function.
fix micorseconds() to support TIME argument
sql/mysql_priv.h:
dead code
sql/time.cc:
dead code
compilation error in mysys/my_getsystime.c fixed
some redundant code removed
sec_to_time, time_to_sec, from_unixtime, unix_timestamp, @@timestamp now
use decimal, not double for numbers with a fractional part.
purge_master_logs_before_date() fixed
many bugs in corner cases fixed
mysys/my_getsystime.c:
compilation failure fixed
sql/sql_parse.cc:
don't cut corners. it backfires.
