group concat tree is allocated in a memroot, so the only way to free
memory is to copy a part of the tree into a new memroot.
track the accumilated length of the result, and when it crosses
the threshold - copy the result into a new tree, free the old one.
Adding an intermediate volatile variable to avoid using co-processor registers
on some platforms (e.g. 32-bit x86).
This change makes test results stable accross all platforms.
multiple times with different arguments.
If the ON expression of an outer join is an OR formula with one
of the disjunct being a constant formula then the expression
cannot be null-rejected if the constant formula is true. Otherwise
it can be null-rejected and if so the outer join can be converted
into inner join. This optimization was added in the patch for
mdev-4817. Yet the code had a defect: if the query was used in
a stored procedure with parameters and the constant item contained
some of them then the value of this constant item depended on the
values of the parameters. With some parameters it may be true,
for others not. The validity of conversion to inner join is checked
only once and it happens only for the first call of procedure.
So if the parameters in the first call allowed the conversion it
was done and next calls used the transformed query though there
could be calls whose parameters made the conversion invalid.
Fixed by cheking whether the constant disjunct in the ON expression
originally contained an SP parameter. If so the expression is not
considered as null-rejected. For this check a new item's attribute
was intruduced: Item::with_param. It is calculated for each item
by fix fields() functions.
Also moved the call of optimize_constant_subqueries() in
JOIN::optimize after the call of simplify_joins(). The reason
for this is that after the optimization introduced by the patch
for mdev-4817 simplify_joins() can use the results of execution
of non-expensive constant subqueries and this is not valid.
We assume all around the code that null_value==true is in sync
with NULL value returned by val_str()/val_decimal().
Item_sum_sum::val_decimal() erroneously returned a non-NULL value together
with null_value set to true. Fixing to return NULL instead.
- Moving Item_xxx_field declarations after Item_sum_xxx declarations,
so Item_xxx_field constructors can be defined directly in item_sum.h
rather than item_sum.cc. This removes some duplicate code, e.g.
initialization of the following members at constructor time:
name, decimals, max_length, unsigned_flag, field, maybe_null.
- Adding Item_sum_field as a common parent for Item_avg_field and
Item_variance_field
- Deriving Item_sum_field directly from Item rather that Item_result_field,
as Item_sum_field descendants do not need anything from Item_result_field.
- Removing hybrid infrastructure from Item_avg_field,
adding Item_avg_field_decimal and Item_avg_field_double instead,
as desired result type is already known at constructor time
(not only at fix_fields time). This simplifies the code.
- Changing Item_avg_field_decimal::val_int() to call val_int_from_decimal()
instead of doing { return (longlong) rint(val_real()); }
This is the fix itself.
The problem was that GROUP BY code created Item_field objects
that referred to fields in the temp. tables used for GROUP BY.
Item_ref and set_items_ref_array() call caused pointers to temp.
table fields to occur in many places.
This patch introduces Item_temptable_field, which can handle
item->print() calls made after the underlying table is freed.
removing IMPOSSIBLE_RESULT from Item_result, as it's not
needed any more. The fact that an Item is not in a comparison
context is now always designated by IDENTITY_SUBST in Subst_constraint.
Previously IMPOSSIBLE_RESULT and IDENTITY_SUBST co-existed but
actually meant the same thing.
- Part 4: Removing calls to sql_alloc() and sql_calloc()
Other things:
- Added current_thd in some places to make it clear that it's called (easier to remove later)
- Move memory allocation from Item_func_case::fix_length_and_dec() to Item_func_case::fix_fields()
- Added mem_root to some new calls
- Fixed some wrong UNINIT_VAR() calls
- Fixed a bug in generate_partition_syntax() in case of errors
- Added mem_root to argument to new thread_info
- Simplified my_parse_error() call in sql_yacc.yy
- Part 3: Adding mem_root to push_back() and push_front()
Other things:
- Added THD as an argument to some partition functions.
- Added memory overflow checking for XML tag's in read_xml()
- Added mem_root to all calls to new Item
- Added private method operator new(size_t size) to Item to ensure that
we always use a mem_root when creating an item.
This saves use once call to current_thd per Item creation
Added mandatory thd parameter to Item (and all derivative classes) constructor.
Added thd parameter to all routines that may create items.
Also removed "current_thd" from Item::Item. This reduced number of
pthread_getspecific() calls from 290 to 177 per OLTP RO transaction.
Correct fix for this bug.
The problem was that Item_func_group_concat() was calling
setup_order(), passing args as the second argument,
ref_pointer_array. While ref_pointer_array should have free
space at the end, as setup_order() can append elements to it.
In this particular case args[] elements were overwritten when
setup_order() was pushing new elements into ref_pointer_array.
execution of PS
GROUP_CONCAT() with ORDER BY column position may crash server on PS reexecution.
The problem was that arguments array of GROUP_CONCAT() was adjusted to point to
temporary elements (resolved ORDER BY fields) during first execution.
This patch expands rev. 08763096cb to restore original arguments array as well.
- Changed ER(ER_...) to ER_THD(thd, ER_...) when thd was known or if there was many calls to current_thd in the same function.
- Changed ER(ER_..) to ER_THD_OR_DEFAULT(current_thd, ER...) in some places where current_thd is not necessary defined.
- Removing calls to current_thd when we have access to thd
Part of this is optimization (not calling current_thd when not needed),
but part is bug fixing for error condition when current_thd is not defined
(For example on startup and end of mysqld)
Notable renames done as otherwise a lot of functions would have to be changed:
- In JOIN structure renamed:
examined_rows -> join_examined_rows
record_count -> join_record_count
- In Field, renamed new_field() to make_new_field()
Other things:
- Added DBUG_ASSERT(thd == tmp_thd) in Item_singlerow_subselect() just to be safe.
- Removed old 'tab' prefix in JOIN_TAB::save_explain_data() and use members directly
- Added 'thd' as argument to a few functions to avoid calling current_thd.