Problem:
At the end of first execution select_lex->prep_where is pointing to
a runtime created object (temporary table field). As a result
server exits trying to access a invalid pointer during second
execution.
Analysis:
While optimizing the join conditions for the query, after the
permanent transformation, optimizer makes a copy of the new
where conditions in select_lex->prep_where. "prep_where" is what
is used as the "where condition" for the query at the start of execution.
W.r.t the query in question, "where" condition is actually pointing
to a field in the temporary table. As a result, for the second
execution the pointer is no more valid resulting in server exit.
Fix:
At the end of the first execution, select_lex->where will have the
original item of the where condition.
Make prep_where the new place where the original item of select->where
has to be rolled back.
Fixed in 5.7 with the wl#7082 - Move permanent transformations from
JOIN::optimize to JOIN::prepare
Patch for 5.5 includes the following backports from 5.6:
Bugfix for Bug12603141 - This makes the first execute statement in the testcase
pass in 5.5
However it was noted later in in Bug16163596 that the above bugfix needed to
be modified. Although Bug16163596 is reproducible only with changes done for
Bug12582849, we have decided include the fix.
Considering that Bug12582849 is related to Bug12603141, the fix is
also included here. However this results in Bug16317817, Bug16317685,
Bug16739050. So fix for the above three bugs is also part of this patch.
__MEMMOVE_SSSE3_BACK FROM STRING::COPY
Issue:
-----
While using row comparators, the store_value functions call
val_xxx functions in the prepare phase. This can cause
valgrind issues.
SOLUTION:
---------
Setting up of the comparators should be done by
alloc_comparators in the prepare phase. Also, make sure
store_value will be called only during execute phase.
This is a backport of the fix for Bug#17755540.
IN IN-CLAUSE USING MYISAM OR MEMORY ENGINE
Backport from 5.6. Original message:
The coincidences caused a data loss:
* The query has IN subqueries nested twice,
* the WHERE clause of the inner subquery refers to the
outer field, and the whole WHERE clause returns FALSE,
* the inner subquery has a LEFT JOIN that joins a single
row with a row of NULLs; one of that NULL columns
represents the select list of the subquery.
Normally, that inner subquery should return empty record set.
However, in our case:
* the Item_is_not_null_test item goes constant, since
its underlying field is NULL (because of LEFT JOIN ... ON
FALSE of const table row with a row of nulls);
* we evaluate Item_is_not_null_test::val_int() as a part
of fake HAVING expression of the transformed subquery;
* as far as the underlying field is NULL, we optimize
out the whole fake HAVING expression as FALSE as well
as a whole subquery with a zero result:
Impossible HAVING noticed after reading const tables";
* thus, the optimizer ignores the presence of the WHERE
clause (the WHERE expression is FALSE in our case, so
the subquery should return empty set);
* however, during the evaluation of the
Item_is_not_null_test::val_int() in the optimizer,
it marked its "owner" with the "was_null" flag -- that
forced the subquery to return UNKNOWN instead of empty
set.
That caused a wrong result.
The problem is a regression of the small cleanup in
the fix for the bug11827369 (the Item_is_not_null_test part)
that conflicts with optimizations in the fix for the bug11752543.
Before that regression the Item_is_not_null_test items
never were constants.
The fix is the rollback of Item_is_not_null_test parts
of the bug11827369 fix.
Some queries with the "SELECT ... FROM DUAL" nested subqueries
failed with an assertion on debug builds.
Non-debug builds were not affected.
There were a few different issues with similar assertion
failures on different queries:
1. The first problem was related to the incomplete propagation
of the "non-constant" item status from underlying subquery
items to the outer item tree: in some cases non-constants were
interpreted as constants and evaluated at the preparation stage
(val_int() calls withing fix_fields() etc).
Thus, the default implementation of Item_ref::const_item() from
the Item parent class didn't take into account the "const_item"
status of the referenced item tree -- it used the insufficient
"used_tables() == 0" check instead. This worked in most cases
since our "non-constant" functions like RAND() and SLEEP() set
the RAND_TABLE_BIT in the used table map, so they aren't
non-constant from Item_ref's "point of view". However, the
"SELECT ... FROM DUAL" subquery may have an empty map of used
tables, but at the same time subqueries are never "constant" at
the context analysis stage (preparation, view creation etc).
So, the non-contantness of such subqueries was missed.
Fix: the Item_ref::const_item() function has been overloaded to
take into account both (*ref)->const_item() status and tricky
Item_ref::used_tables() return values, since the only
(*ref)->const_item() call is not enough there.
2. In some cases instead of the const_item() call we check a
value of the Item::with_subselect field to recognize items
with nested subqueries. However, the Item_ref class didn't
propagate this value from the referenced item tree.
Fix: Item::has_subquery() and Item_ref::has_subquery()
functions have been backported from 5.6. All direct
references to the with_subselect fields of nested items have
been with the has_subquery() function call.
3. The Item_func_regex class didn't propagate with_subselect
as well, since it overloads the Item_func::fix_fields()
function with insufficient fix_fields() implementation.
Fix: the Item_func_regex::fix_fields() function has been
modified to gather "constant" statuses from inner items.
4. The Item_func_isnull::update_used_tables() function has
a special branch for the underlying item where the maybe_null
value is false: in this case it marks the Item_func_isnull
as a "const_item" and sets the cached_value to false.
However, the Item_func_isnull::val_int() was not in sync with
update_used_tables(): it didn't take into account neither
const_item_cache nor cached_value for the case of
"args[0]->maybe_null == false optimization".
As far as such an Item_func_isnull has "const_item() == true",
it's ok to call Item_func_isnull::val_int() etc from outer
items on preparation stage. In this case the server tried to
call Item_func_isnull::args[0]->isnull(), and if the args[0]
item contained a nested not-nullable subquery, it failed
with an assertion.
Fix: take the value of Item_func_isnull::const_item_cache into
account in the val_int() function.
5. The auxiliary Item_is_not_null_test class has a similar
optimization in the update_used_tables() function as the
Item_func_isnull class has, and the same issue in the val_int()
function.
In addition to that the Item_is_not_null_test::update_used_tables()
doesn't update the const_item_cache value, so the "maybe_null"
optimization is useless there. Thus, we missed some optimizations
of cases like these (before and after the fix):
< <is_not_null_test>(a),
---
> <cache>(<is_not_null_test>(a)),
or
< having (<is_not_null_test>(a) and <is_not_null_test>(a))
---
> having 1
etc.
Fix: update Item_is_not_null_test::const_item_cache in
update_used_tables() and take in into account in val_int().
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.
Issue/Cause:
Issue is of memory corruption.During optimization phase, pattern to be matched in where
clause, is prepared. This is done in Item_func_concat::val_str() function which forms the
resultant string (tmp_value) and return its pointer. In caller, Item_func_like::fix_fields,
pattern is made to point to this string (tmp_value). In further processing, tmp_value is
getting modified which causes pattern to have changed/wrong values.
Fix:
Allocate its own memroy location in caller, copy value of resultant string (tmp_value)
into that and make pattern to point to that. This makes sure no further changes to
tmp_value will affect pattern.
Bug#11758543 50756: BIGINT '100' MATCHES 1.001E2
Expressions of the form
BIGINT_COL <compare> <non-integer constant>
should be done either as decimal, or float.
Currently however, such comparisons are done as int,
which means that the constant may be truncated,
and yield false positives/negatives for all queries
where compare is '>' '<' '>=' '<=' '=' '!='.
BIGINT_COL IN <list of contstants>
and
BIGINT_COL BETWEEN <constant> AND <constant>
are also affected.
OLD VALUE OF INPUT PARAMETER.
The user-visible problem was that CASE-control-flow function
(not CASE-statement) misbehaved in stored routines under some
circumstances. The problem resulted in a crash or wrong data
returned. The error happened when expressions in CASE-function
were not of the same character set.
A CASE-function should return values of the same character set
for all branches. Internally, that means a new Item-instance
for the CONVERT(... USING <some charset>)-function is added
to the item tree when needed. The problem was that such changes
were not properly recorded using THD::change_item_tree(),
thus dangling pointers remain in the item tree after
THD::rollback_item_tree_changes(), which lead to undefined
behavior (i.e. crash / wrong data) for subsequent executions of
the stored routine.
This bug was introduced by a patch for Bug 11753363
(44793 - CHARACTER SETS: CASE CLAUSE, UCS2 OR UTF32, FAILURE).
The fixed function is Item_func_case::fix_length_and_dec().
New CONVERT-items are added in agg_item_set_converter(),
which calls THD::change_item_tree().
The problem was that an intermediate array was passed
to agg_item_set_converter(). Thus, THD::change_item_tree() there
was called on intermediate objects.
Note: those intermediate objects are allocated on THD's
memory root, so it's Ok to put them into "changed item lists".
The fix is to track changes on the correct objects.
(SUBSTRING inside a stored function works too slow).
Background:
- THD classes derives from Query_arena, thus inherits the 'state'
attribute and related operations (is_stmt_prepare() & co).
- Although these operations are available in THD, they must not
be used. THD has its own attribute to point to the active
Query_arena -- stmt_arena.
- So, instead of using thd->is_stmt_prepare(),
thd->stmt_arena->is_stmt_prepare() must be used. This was the root
cause of Bug 60025.
This patch enforces the proper way of calling those operations.
is_stmt_prepare() & co are declared as private operations
in THD (thus, they are hidden from being called on THD instance).
The patch tries to minimize changes in 5.5.
Valgrind warning happens due to early null values check
in Item_func_in::fix_length_and_dec(before item evaluation).
As result null value items with uninitialized values are
placed into array and it leads to valgrind warnings during
value array sorting.
The fix is to check null value after item evaluation, item
is evaluated in in_array::set() method.
Problem: in case of string CASE/WHEN arguments with different
character sets, Item_func_case::find_item() called comparator
cmp_items[x] on mixed character set Items, so a 8-bit value could
be errouneously referenced to as being utf16/utf32 value,
which led to crash on DBUG_ASSERT() because of wrong value length.
This was wrong, as string comparator expects arguments in the same
character set.
Fix: modify Item_func_case's argument list after calling
agg_arg_charsets_for_comparison() - put the Items in "agg" array
back to "args", because some of the Items in the "agg" array might
have been changed to character set converters:
- to Item_func_conv_charset for non-constant items
- to Item_string for constant items
In other words, perform the same substitution which is done in
all other operations string comparison or string result operations:
Replace
CASE latin1_item WHEN utf16_item THEN ... END
to
CASE CONVERT(latin1_item USING utf16) WHEN utf16_item THEN ... END
Replace
CASE utf16_item WHEN latin1_item THEN ... END
to
CASE utf16_item WHEN CONVERT(latin1_item USING utf16) THEN ... END
@ mysql-test/r/ctype_utf16.result
@ mysql-test/r/ctype_utf32.result
@ mysql-test/t/ctype_utf16.test
@ mysql-test/t/ctype_utf32.test
Adding tests
@ sql/item_cmpfunc.cc
Put "agg" back to "args".
@ sql/sql_string.cc
Backporting a fix for String::set_or_copy_aligned() from 5.6,
for better test coverage:
"SELECT _utf16 0x61" should expand the string to 0x0061 rather
than to 0x000061.
This fix was made in 5.6 under terms of "WL#4616 Implement UTF16-LE".
Problem:
IF() did not copy collation derivation and repertoire from
an argument if the opposite argument was NULL:
IF(cond, res1, NULL)
IF(cond, NULL, res2)
only CHARSET_INFO pointer was copied.
This resulted in illegal mix of collations error.
Fix:
copy all collation parameters from the non-NULL argument:
CHARSET_INFO pointer, derivation, repertoire.
ZERO
When dates are represented internally as strings, i.e. when a string constant
is compared to a date value, both values are converted to long integers,
ostensibly for fast comparisons. DATE typed integer values are converted to
DATETIME by multiplying by 1,000,000 (each digit pair representing hour,
minute and second, respectively). But the mechanism did not distuinguish
cached INTEGER values, already in correct format, from newly converted
strings.
Fixed by marking the INTEGER cache as being of DATETIME format.
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.)
Item_equal::val_int() checked for NULL-values by checking Item::null_value
*before* the respective ::store_value() and ::cmp(Item*) metods where called.
As Item::null_value is set by these metods, the value of 'null_value'
is not valid until *after* ::store_value() or ::cmp() has
been called for the Item object.
Fix is to swap order of ::store_value()/::cmp() and checking of Item::null_value.
This pattern is widely used other places inside item_cmpfunc.cc .
- 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.
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
Problem: CASE didn't work with a mixture of different character
sets in THEN/ELSE in some cases.
This happened because after character set aggregation
newly created Item_func_conv_charset items corresponding
to THEN/ELSE arguments were not put back to args[] array.
Fix:
put all Item_func_conv_charset back to args[].
@ mysql-test/include/ctype_numconv.inc
@ mysql-test/r/ctype_ucs.result
Adding tests
@ sql/item_cmpfunc.cc
Put "agg" back to args[] after character set aggregation.
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.
file .\dtoa.c
The assertion failure was correct because the 'width' argument
of my_gcvt() has the signed integer type, whereas the unsigned
value UINT_MAX32 was being passed by the caller
(Field_double::val_str()) leading to a negative width in
my_gcvt().
The following chain of problems was found by further analysis:
1. The display width for a floating point number is calculated
in Field_double::val_str() as either field_length or the
maximum possible length of string representation of a floating
point number, whichever is greater. Since in the bug's test
case field_length is UINT_MAX32, we get the same value as the
display width. This does not make any sense because for numeric
values field_length only matters for ZEROFILL columns,
otherwise it does not make sense to allocate that much memory
just to print a number. Field_float::val_str() has a similar
problem.
2. Even if the above wasn't the case, we would still get a
crash on a slightly different test case when trying to allocate
UINT_MAX32 bytes with String::alloc() because the latter does
not handle such large input values correctly due to alignment
overflows.
3. Even when String::alloc() is fixed to return an error when
an alignment overflow occurs, there is still a problem because
almost no callers check its return value, and
Field_double::val_str() is not an exception (same for
Field_float::val_str()).
4. Even if all of the above wasn't the case, creating a
Field_double object with UINT_MAX32 as its field_length does
not make much sense either, since the .frm code limits it to
MAX_FIELD_CHARLENGTH (255) bytes. Such a beast can only be
created by create_tmp_field_from_item() from an Item with
REAL_RESULT as its result_type() and UINT_MAX32 as its
max_length.
5. For the bug's test case, the above condition (REAL_RESULT
Item with max_length = UINT_MAX32) was a result of
Item_func_if::fix_length_and_dec() "shortcutting" aggregation
of argument types when one of the arguments was a constant
NULL. In this case, the attributes of the aggregated type were
simply copied from the other, non-NULL argument, but max_length
was still calculated as per the general, non-shortcut case, by
choosing the greatest of argument's max_length, which is
obviously not correct.
The patch addresses all of the above problems, even though
fixing the assertion failure for the particular test case would
require only a subset of the above problems to be solved.
Problem: a few functions did not calculate their max_length correctly.
This is an after-fix for WL#2649 Number-to-string conversions".
Fix: changing the buggy functions to calculate max_length
using fix_char_length() introduced in WL#2649,
instead of setting max_length directly
mysql-test/include/ctype_numconv.inc
Adding new tests
mysql-test/r/ctype_binary.result
Adding new tests
mysql-test/r/ctype_cp1251.result
Adding new tests
mysql-test/r/ctype_latin1.result
Adding new tests
mysql-test/r/ctype_ucs.result
Adding new tests
mysql-test/r/ctype_utf8.result
Adding new tests
mysql-test/t/ctype_utf8.test
Including ctype_numconv
sql/item.h
- Introducing new method fix_char_length_ulonglong(),
for the cases when length is potentially greater
than UINT_MAX32. This method removes a few
instances of duplicate code, e.g. in item_strfunc.cc.
- Setting collation in Item_copy properly. This change
fixes wrong metadata on client side in some cases, when
"binary" instead of the real character set was reported.
sql/item_cmpfunc.cc
- Using fix_char_length() and max_char_length() methods,
instead of direct access to max_length, to calculate
item length properly.
- Moving count_only_length() in COALESCE after
agg_arg_charsets_for_string_result(). The old
order was incorrect and led to wrong length
calucation in case of multi-byte character sets.
sql/item_func.cc
Fixing that count_only_length() didn't work
properly for multi-byte character sets.
Using fix_char_length() and max_char_length()
instead of direct access to max_length.
sql/item_strfunc.cc
- Using fix_char_length(), fix_char_length_ulonglong(),
max_char_length() instead of direct access to max_length.
- Removing wierd condition: "if (collation.collation->mbmaxlen > 0)",
which is never FALSE.
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.
This bug is a design flaw of the fix for the bug#33546. It assumed that an
item can be used only in one comparison context, but actually it isn't the
case. Item_cache_datetime is used to store result for MIX/MAX aggregate
functions. Because Arg_comparator always compares datetime values as INTs when
possible the Item_cache_datetime most time caches only INT value. But
since all datetime values has STRING result type MIN/MAX functions are asked
for a STRING value when the result is being sent to a client. The
Item_cache_datetime was designed to avoid conversions and get INT/STRING
values from an underlying item, but at the moment the values is asked
underlying item doesn't hold it anymore thus wrong result is returned.
Beside that MIN/MAX aggregate functions was wrongly initializing cached result
and this led to a wrong result.
The Item::has_compatible_context helper function is added. It checks whether
this and given items has the same comparison context or can be compared as
DATETIME values by Arg_comparator. The equality propagation optimization is
adjusted to take into account that items which being compared as DATETIME
can have different comparison contexts.
The Item_cache_datetime now converts cached INT value to a correct STRING
DATETIME value by means of number_to_datetime & my_TIME_to_str functions.
The Arg_comparator::set_cmp_context_for_datetime helper function is added.
It sets comparison context of items being compared as DATETIMEs to INT if
items will be compared as longlong.
The Item_sum_hybrid::setup function now correctly initializes its result
value.
In order to avoid unnecessary conversions Item_sum_hybrid now states that it
can provide correct longlong value if the item being aggregated can do it
too.
