The SQL layer never acquires metadata locks (MDL) on the tables
that the tables that DML statement accesses is modifying.
However, the storage engine must access the parent table in order to
ensure that the child table will not refer to a non-existing record
in the parent table.
During certain DDL operations, the InnoDB table metadata (dict_table_t)
may be be freed and rebuilt. This would cause a race condition with
a concurrent INSERT that is attempting to report a FOREIGN KEY violation.
We work around the insufficient MDL during DML by acquiring exclusive
InnoDB table locks on all child tables during DDL. To avoid deadlocks,
we will follow the following order of acquisition:
1. tables whose REFERENCES clauses point to the current table
2. the current table that is being subjected to DDL
3. mysql.innodb_table_stats
4. mysql.innodb_index_stats
5. the InnoDB dictionary tables (SYS_TABLES and so on)
6. exclusive dict_sys.latch
Buffer overflow in ib_push_warning() fixed by using vsnprintf().
InnoDB parser was obsoleted by MDEV-16417.
Thanks to Nikita Malyavin for review and suggestion.
The reason for the failure is that
thd->mdl_context.release_transactional_locks()
was called after commit & rollback even in cases where the current
transaction is still active.
For 10.2, 10.3 and 10.4 the fix is simple:
- Replace all calls to thd->mdl_context.release_transactional_locks() with
thd->release_transactional_locks(). The thd function will only call
the mdl_context function if there are no active transactional locks.
In 10.6 we will better fix where we will change the return value for
some trans_xxx() functions to indicate if transaction did close the
transaction or not. This will avoid the need of the indirect call.
Other things:
- trans_xa_commit() and trans_xa_rollback() will automatically
call release_transactional_locks() if the transaction is closed.
- We can't do that for the other functions as the caller of many of these
are doing additional work (like close_thread_tables) before calling
release_transactional_locks().
- Added missing abort_result_set() and missing DBUG_RETURN in
select_create::send_eof()
- Fixed wrong indentation in injector::transaction::commit()
Marking of deletion of row in fts index happens twice in
self-referential foreign key relation. So while performing
referential checks of foreign key, InnoDB can avoid updating
of fts index if the foreign key has self-referential relationship.
Reviewed-by: Marko Mäkelä
- During insertion of clustered inde, InnoDB does the check for
foreign key constraints. It rebuild the tuple based on foreign
column names when there is no foreign index. While rebuilding,
InnoDB should ignore the dropped columns.
dict_foreign_qualify_index(): Reject corrupted or garbage indexes.
For index stubs that are created on virtual columns, no
dict_field_t::col would be assign. Instead, the entire table
definition would be reloaded on a successful operation.
Problem:
=======
InnoDB drops the column which has foreign key relations on it. So it
tries to load the foreign key during rename process of copy algorithm
even though the foreign_key_check is disabled.
Solution:
========
During alter copy algorithm, InnoDB ignores the error while loading
the foreign key constraint if foreign key check is disabled. It
should throw the warning about failure of the foreign key constraint
when foreign key check is disabled.
CHECK constraint is checked by check_expression() which walks its
items and gets into Item_field::check_vcol_func_processor() to check
for conformity with foreign key list.
WITHOUT OVERLAPS is checked for same conformity in
mysql_prepare_create_table().
Long uniques are already impossible with InnoDB foreign keys. See
ER_CANT_CREATE_TABLE in test case.
2 accompanying bugs fixed (test main.constraints failed):
1. check->name.str lived on SP execute mem_root while "check" obj
itself lives on SP main mem_root. On second SP execute check->name.str
had garbage data. Fixed by allocating from thd->stmt_arena->mem_root
which is SP main mem_root.
2. CHECK_CONSTRAINT_IF_NOT_EXISTS value was mixed with
VCOL_FIELD_REF. VCOL_FIELD_REF is assigned in check_expression() and
then detected as CHECK_CONSTRAINT_IF_NOT_EXISTS in
handle_if_exists_options().
Existing cases for MDEV-16932 in main.constraints cover both fixes.
FOREIGN_KEY_CHECKS is disabled
- Referenced index can be null While renaming the referenced column name.
In that case, rename the referenced column name in dict_foreign_t and
find the equivalent referenced index.
In main.index_merge_myisam we remove the test that was added in
commit a2d24def8c because
it duplicates the test case that was added in
commit 5af12e4635.
FOREIGN_KEY_CHECKS is disabled
- dict_foreign_find_index() can return NULL if InnoDB already dropped
the foreign index when FOREIGN_KEY_CHECKS is disabled.
