[#MDEV-12568] Add Type_handler::subquery_type_allows

    switch (outer->cmp_type()) {

    case STRING_RESULT:

      if (!(outer->collation.collation == inner->collation.collation))

        DBUG_RETURN(FALSE);

      // Materialization does not work with BLOB columns

      if (inner->field_type() == MYSQL_TYPE_BLOB ||

          inner->field_type() == MYSQL_TYPE_GEOMETRY)

        DBUG_RETURN(FALSE);

/*

        Materialization also is unable to work when create_tmp_table() will

        create a blob column because item->max_length is too big.

        The following check is copied from Item::make_string_field():

*/

      if (inner->too_big_for_varchar())

        DBUG_RETURN(FALSE);

      break;

    case TIME_RESULT:

      if (mysql_type_to_time_type(outer->field_type()) !=

          mysql_type_to_time_type(inner->field_type()))

        DBUG_RETURN(FALSE);

    default:

      /* suitable for materialization */

      break;

It's not friendly for new data types. It uses a switch on cmp_type() and uses mysql_type_to_time_type(outer->field_type()).

virtual enum_mysql_timestamp_type mysql_timestamp_type() const;

virtual bool subquery_type_allows_materialization(const Item *inner, const Item *outer) const;

2. Split the above code into virtual implementations for corresponding type handlers.

3. Replace calls mysql_type_to_time_type(field_type()) to type_handler()->mysql_timestamp_type()

[MDEV-12568] Add Type_handler::subquery_type_allows_materialization() Created: 2017-04-23 Updated: 2017-04-24 Resolved: 2017-04-24
Status:	Closed
Project:	MariaDB Server
Component/s:	Optimizer
Fix Version/s:	10.3.1