MySQL 5.7 supports only one shared temporary tablespace.
MariaDB 10.2 does not support any other shared InnoDB tablespaces than the two predefined tablespaces: the persistent InnoDB system tablespace (default file name ibdata1) and the temporary tablespace (default file name ibtmp1).
InnoDB is unnecessarily allocating a tablespace ID for the predefined temporary tablespace on every startup, and it is in several places testing whether a tablespace ID matches this dynamically generated ID.
We should use a compile-time constant to reduce code size and to avoid unnecessary updates to the DICT_HDR page at every startup.
Using a hard-coded tablespace ID will also make it easier to remove the TEMPORARY flag from FSP_SPACE_FLAGS in