Method join_cache_allowed

sql/json_table.h:234–242

  table_map used_tables() const { return m_json->used_tables(); }
  bool join_cache_allowed() const
  {
    /*
      Can use join cache when we have an outside reference.
      If there's dependency on any other table or randomness,
      cannot use it.
    */
    return !(used_tables() & ~OUTER_REF_TABLE_BIT);
  }
  void get_estimates(ha_rows *out_rows,
                     double *scan_time, double *startup_cost);