MDEV-30932 UBSAN: negation of -X cannot be represented in type ..
'long long int'; cast to an unsigned type to negate this value ..
to itself in Item_func_mul::int_op and Item_func_round::int_op
Problems:
The code in multiple places in the following methods:
- Item_func_mul::int_op()
- longlong Item_func_int_div::val_int()
- Item_func_mod::int_op()
- Item_func_round::int_op()
did not properly check for corner values LONGLONG_MIN
and (LONGLONG_MAX+1) before doing negation.
This cuased UBSAN to complain about undefined behaviour.
Fix summary:
- Adding helper classes ULonglong, ULonglong_null, ULonglong_hybrid
(in addition to their signed couterparts in sql/sql_type_int.h).
- Moving the code performing multiplication of ulonglong numbers
from Item_func_mul::int_op() to ULonglong_hybrid::ullmul().
- Moving the code responsible for extracting absolute values
from negative numbers to Longlong::abs().
It makes sure to perform negation without undefinite behavior:
LONGLONG_MIN is handled in a special way.
- Moving negation related code to ULonglong::operator-().
It makes sure to perform negation without undefinite behavior:
(LONGLONG_MAX + 1) is handled in a special way.
- Moving signed<=>unsigned conversion code to
Longlong_hybrid::val_int() and ULonglong_hybrid::val_int().
- Reusing old and new sql_type_int.h classes in multiple
places in Item_func_xxx::int_op().
Fix details (explain how sql_type_int.h classes are reused):
- Instead of straight negation of negative "longlong" arguments
*before* performing unsigned multiplication,
Item_func_mul::int_op() now calls ULonglong_null::ullmul()
using Longlong_hybrid_null::abs() to pass arguments.
This fixes undefined behavior N1.
- Instead of straight negation of "ulonglong" result
*after* performing unsigned multiplication,
Item_func_mul::int_op() now calls ULonglong_hybrid::val_int(),
which recursively calls ULonglong::operator-().
This fixes undefined behavior N2.
- Removing duplicate negating code from Item_func_mod::int_op().
Using ULonglong_hybrid::val_int() instead.
This fixes undefinite behavior N3.
- Removing literal "longlong" negation from Item_func_round::int_op().
Using Longlong::abs() instead, which correctly handler LONGLONG_MIN.
This fixes undefinite behavior N4.
- Removing the duplicate (negation related) code from
Item_func_int_div::val_int(). Reusing class ULonglong_hybrid.
There were no undefinite behavior in here.
However, this change allowed to reveal a bug in
"-9223372036854775808 DIV 1".
The removed negation code appeared to be incorrect when
negating +9223372036854775808. It returned the "out of range" error.
ULonglong_hybrid::operator-() now handles all values correctly
and returns +9223372036854775808 as a negation for -9223372036854775808.
Re-recording wrong results for
SELECT -9223372036854775808 DIV 1;
Now instead of "out of range", it returns -9223372036854775808,
which is the smallest possible value for the expression data type
(signed) BIGINT.
- Removing "no UBSAN" branch from Item_func_splus::int_opt()
and Item_func_minus::int_opt(), as it made UBSAN happy but
in RelWithDebInfo some MTR tests started to fail.
MDEV-31086 MODIFY COLUMN can break FK constraints, and lead to unrestorable dumps
- When foreign_key_check is disabled, allowing to modify the
column which is part of foreign key constraint can lead to
refusal of TRUNCATE TABLE, OPTIMIZE TABLE later. So it make
sense to block the column modify operation when foreign key
is involved irrespective of foreign_key_check variable.
Correct way to modify the charset of the column when fk is involved:
SET foreign_key_checks=OFF;
ALTER TABLE child DROP FOREIGN KEY fk, MODIFY m VARCHAR(200) CHARSET utf8mb4;
ALTER TABLE parent MODIFY m VARCHAR(200) CHARSET utf8mb4;
ALTER TABLE child ADD CONSTRAINT FOREIGN KEY (m) REFERENCES PARENT(m);
SET foreign_key_checks=ON;
fk_check_column_changes(): Remove the FOREIGN_KEY_CHECKS while
checking the column change for foreign key constraint. This
is the partial revert of commit 5f1f2fc0e443f098af24d21f7d1ec1a8166a4030
and it changes the behaviour of copy alter algorithm
ha_innobase::prepare_inplace_alter_table(): Find the modified
column and check whether it is part of existing and newly
added foreign key constraint.
MDEV-29447 MDEV-26285 MDEV-31338 Refactor spider_db_mbase_util::open_item_func
spider_db_mbase_util::open_item_func() is a monster function.
It is difficult to maintain while it is expected that we need to
modify it when a new SQL function or a new func_type is added.
We split the function into two distinct functions: one handles the
case of str != NULL and the other handles the case of str == NULL.
This refactoring was done in a conservative way because we do not
have comprehensive tests on the function.
It also fixes MDEV-29447 and MDEV-31338 where field items that are
arguments of a func item may be used before created / initialised.
Note this commit is adapted from a patch by Nayuta for MDEV-26285.
