Function fk_prepare_copy_alter_table

sql/sql_table.cc:9849–10101

*/

static bool fk_prepare_copy_alter_table(THD *thd, TABLE *table,
                                        Alter_info *alter_info,
                                        Alter_table_ctx *alter_ctx)
{
  List <FOREIGN_KEY_INFO> fk_parent_key_list;
  List <FOREIGN_KEY_INFO> fk_child_key_list;
  FOREIGN_KEY_INFO *f_key;

  DBUG_ENTER("fk_prepare_copy_alter_table");

  table->file->get_parent_foreign_key_list(thd, &fk_parent_key_list);

  /* OOM when building list. */
  if (unlikely(thd->is_error()))
    DBUG_RETURN(true);

  /*
    Remove from the list all foreign keys in which table participates as
    parent which are to be dropped by this ALTER TABLE. This is possible
    when a foreign key has the same table as child and parent.
  */
  List_iterator<FOREIGN_KEY_INFO> fk_parent_key_it(fk_parent_key_list);
  List<FOREIGN_KEY_INFO> keys_to_remove;

  while ((f_key= fk_parent_key_it++))
  {
    Alter_drop *drop;
    List_iterator_fast<Alter_drop> drop_it(alter_info->drop_list);

    while ((drop= drop_it++))
    {
      /*
        InnoDB treats foreign key names in case-insensitive fashion.
        So we do it here too. For database and table name type of
        comparison used depends on lower-case-table-names setting.
        For l_c_t_n = 0 we use case-sensitive comparison, for
        l_c_t_n > 0 modes case-insensitive comparison is used.
      */
      if ((drop->type == Alter_drop::FOREIGN_KEY) &&
          drop->name.streq(*f_key->foreign_id) &&
          table->s->db.streq(*f_key->foreign_db) &&
          table->s->table_name.streq(*f_key->foreign_table))
      {
        keys_to_remove.push_back(f_key);
        break;
      }
    }
  }

  IF_DBUG(uint removed= 0,);
  /* Remove the identified keys */
  List_iterator<FOREIGN_KEY_INFO> remove_it(keys_to_remove);
  while ((f_key = remove_it++))
  {
    fk_parent_key_it.rewind();
    while (FOREIGN_KEY_INFO *fk= fk_parent_key_it++)
    {
      if (fk == f_key)