default_tmp_storage_engine
variable was introduced
in 5.6.3, allowing the configuration of the default engine for
temporary tables. This seems to be in the direction, as I
commented before, of making MyISAM an optional engine. In 5.7,
a separate tablespace is being created to hold
those tables in order to reduce its performance penalty
(those tables do not need to be redone if the server crashes, so
extra writes are avoided).
However, I have seen many people assuming that because
default_tmp_storage_engine
has the value “InnoDB”,
all temporary tables are created in InnoDB format in
5.6. This is not true: first, because implicit
temporary tables are still being created in memory using …