CHECK OPTION and a subquery in WHERE condition.
The abort was triggered by setting the value of join->tables for
subqueries in the function JOIN::cleanup. This function was called
after an invocation of the JOIN::join_free method for subqueries
used in WHERE condition.
The problem reported is a compile bug,
reported by the development GCC team with GCC 4.2.
The original issue can no longer be reproduced in MySQL 5.1,
since the configure script no longer define HAVE_ATOMIC_ADD,
which caused the Linux atomic functions to be used (and cause a problem
with an invalid cast).
This patch implements some code cleanup for 5.1 only, which was identified
during the investigation of this issue.
With this patch, statistics maintained in THD::status_var are by definition
owned by the running thread, and do not need to be protected against race
conditions. These statistics are maintained by the status_var_* helpers,
which do not require any lock.
When processing the USE/FORCE index hints
the optimizer was not checking if the indexes
specified are enabled (see ALTER TABLE).
Fixed by:
Backporting the fix for bug 20604 to 5.0
for a query over an empty table right after its creation.
The crash is the result of an attempt made by JOIN::optimize to evaluate
the WHERE condition when no records have been actually read.
The added test case can reproduce the crash only with InnoDB tables and
only with 5.0.x.
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
- added join cache indication in EXPLAIN (Extra column).
- prefer filesort over full scan over
index for ORDER BY (because it's faster).
- when switching from REF to RANGE because
RANGE uses longer key turn off sort on
the head table only as the resulting
RANGE access is a candidate for join cache
and we don't want to disable it by sorting
on the first table only.
When checking for applicability of join cache
we must disable its usage only if there is no
temp table in use.
When a temp table is used we can use join
cache (and it will not make the result-set
unordered) to fill the temp table. The filesort()
operation is then applied to the data in the temp
table and hence is not affected by join cache
usage.
Fixed by narrowing the condition for disabling
join cache to exclude the case where temp table
is used.
Non-correlated scalar subqueries may get executed
in EXPLAIN at the optimization phase if they are
part of a right hand sargable expression.
If the scalar subquery uses a temp table to
materialize its results it will replace the
subquery structure from the parser with a simple
select from the materialization table.
As a result the EXPLAIN will crash as the
temporary materialization table is not to be shown
in EXPLAIN at all.
Fixed by preserving the original query structure
right after calling optimize() for scalar subqueries
with temp tables executed during EXPLAIN.
'not exists' optimization is applied.
In fact 'not exists' optimization did not work anymore after the patch
introducing the evaluate_join_record function had been applied.
Corrected the evaluate_join_record function to respect the 'not_exists'
optimization.
some rollup rows (rows with NULLs for grouping attributes) if GROUP BY
list contained constant expressions.
This happened because the results of constant expressions were not put
in the temporary table used for duplicate elimination. In fact a constant
item from the GROUP BY list of a ROLLUP query can be replaced for an
Item_null_result object when a rollup row is produced .
Now the JOIN::rollup_init function wraps any constant item referenced in
the GROYP BY list of a ROLLUP query into an Item_func object of a special
class that is never detected as constant item. This ensures creation of
fields for such constant items in temporary tables and guarantees right
results when the result of the rollup operation first has to be written
into a temporary table, e.g. in the cases when duplicate elimination is
required.
DATE and DATETIME can be compared either as strings or as int. Both
methods have their disadvantages. Strings can contain valid DATETIME value
but have insignificant zeros omitted thus became non-comparable with
other DATETIME strings. The comparison as int usually will require conversion
from the string representation and the automatic conversion in most cases is
carried out in a wrong way thus producing wrong comparison result. Another
problem occurs when one tries to compare DATE field with a DATETIME constant.
The constant is converted to DATE losing its precision i.e. losing time part.
This fix addresses the problems described above by adding a special
DATE/DATETIME comparator. The comparator correctly converts DATE/DATETIME
string values to int when it's necessary, adds zero time part (00:00:00)
to DATE values to compare them correctly to DATETIME values. Due to correct
conversion malformed DATETIME string values are correctly compared to other
DATE/DATETIME values.
As of this patch a DATE value equals to DATETIME value with zero time part.
For example '2001-01-01' equals to '2001-01-01 00:00:00'.
The compare_datetime() function is added to the Arg_comparator class.
It implements the correct comparator for DATE/DATETIME values.
Two supplementary functions called get_date_from_str() and get_datetime_value()
are added. The first one extracts DATE/DATETIME value from a string and the
second one retrieves the correct DATE/DATETIME value from an item.
The new Arg_comparator::can_compare_as_dates() function is added and used
to check whether two given items can be compared by the compare_datetime()
comparator.
Two caching variables were added to the Arg_comparator class to speedup the
DATE/DATETIME comparison.
One more store() method was added to the Item_cache_int class to cache int
values.
The new is_datetime() function was added to the Item class. It indicates
whether the item returns a DATE/DATETIME value.
This bug was intruduced by the fix for bug#17212 (in 4.1). It is not
ok to call test_if_skip_sort_order since this function will
alter the execution plan. By contract it is not ok to call
test_if_skip_sort_order in this context.
This bug appears only in the case when the optimizer has chosen
an index for accessing a particular table but finds a covering
index that enables it to skip ORDER BY. This happens in
test_if_skip_sort_order.
The Item_outer_ref class based on the Item_direct_ref class was always used
to represent an outer field. But if the outer select is a grouping one and the
outer field isn't under an aggregate function which is aggregated in that
outer select an Item_ref object should be used to represent such a field.
If the outer select in which the outer field is resolved isn't grouping then
the Item_field class should be used to represent such a field.
This logic also should be used for an outer field resolved through its alias
name.
Now the Item_field::fix_outer_field() uses Item_outer_field objects to
represent aliased and non-aliased outer fields for grouping outer selects
only.
Now the fix_inner_refs() function chooses which class to use to access outer
field - the Item_ref or the Item_direct_ref. An object of the chosen class
substitutes the original field in the Item_outer_ref object.
The direct_ref and the found_in_select_list fields were added to the
Item_outer_ref class.
The optimizer transforms DISTINCT into a GROUP BY
when possible.
It does that by constructing the same structure
(a list of ORDER instances) the parser makes when
parsing GROUP BY.
While doing that it also eliminates duplicates.
But if a duplicate is found it doesn't advance the
pointer to ref_pointer array, so the next
(and subsequent) ORDER structures point to the wrong
element in the SELECT list.
Fixed by advancing the pointer in ref_pointer_array
even in the case of a duplicate.
