code: protected function findPrimaryKeys($table)
      {
          $result = [];
          foreach ($this->findTableConstraints($table, 'PRIMARY KEY') as $row) {
              $result[] = $row['field_name'];
          }
          $table->primaryKey = $result;
      }
docs: Collects the primary key column details for the given table.
  @param TableSchema $table the table metadata