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
Don't allow the referencing key column from NULL TO NOT NULL
when
1) Foreign key constraint type is ON UPDATE SET NULL
2) Foreign key constraint type is ON DELETE SET NULL
3) Foreign key constraint type is UPDATE CASCADE and referenced
column declared as NULL
Don't allow the referenced key column from NOT NULL to NULL
when foreign key constraint type is UPDATE CASCADE
and referencing key columns doesn't allow NULL values
get_foreign_key_info(): InnoDB sends the information about
nullability of the foreign key fields and referenced key fields.
fk_check_column_changes(): Enforce the above rules for COPY
algorithm
innobase_check_foreign_drop_col(): Checks whether the dropped
column exists in existing foreign key relation
innobase_check_foreign_low() : Enforce the above rules for
INPLACE algorithm
dict_foreign_t::check_fk_constraint_valid(): This is used
by CREATE TABLE statement to check nullability for foreign
key relation.
