Before MySQL 4.0.18, user-specified constraint names were ignored.
Starting with MySQL 4.0.18, the specified constraint name was
prepended with the schema name and '/'. Now we are transforming
into a format where the constraint name is prepended with the
dict_table_t::name and the impossible UTF-8 sequence 0xff.
Generated constraint names will be ASCII decimal numbers.
On upgrade, old FOREIGN KEY constraint names will be displayed
without any schema name prefix. They will be updated to the new
format on DDL operations.
dict_foreign_t::sql_id(): Return the SQL constraint name
without any schemaname/tablename\377 or schemaname/ prefix.
row_rename_table_for_mysql(), dict_table_rename_in_cache():
Simplify the logic: Just rename constraints to the new format.
dict_table_get_foreign_id(): Replaces dict_table_get_highest_foreign_id().
innobase_get_foreign_key_info(): Let my_error() refer to erroneous
anonymous constraints as "(null)".
row_delete_constraint(): Try to drop all 3 constraint name variants.
Reviewed by: Thirunarayanan Balathandayuthapani
Tested by: Matthias Leich
Problem:
If we add a referential integrity constraint with a duplicate
name, an error occurs. The foreign key object would not have
been added to the dictionary cache. In the error path, there
is an attempt to remove this foreign key object. Since this
object is not there, the search returns a NULL result.
De-referencing the null object results in this crash.
Solution:
If the search to the foreign key object failed, then don't
attempt to access it.
rb#9309 approved by Marko.
