'derived_merge':
- if the flag is off then all derived tables are materialized
- if the flag is on then mergeable derived tables are merged
'derived_with_keys':
- if the flag is off then no keys are created for derived tables
- if the flag is on then for any derived table a key to access
the derived table may be created.
Now by default both flags are on.
Later the default values for the flags will be off to comply with
the current behaviour of mysql-5.1.
Uncommented previously commented out test case from parts.partition_repair_myisam
after having added an explicit requirement to materialize the derived
table used in the test case.
When this flag is 'off' the size of the used join buffer
is taken directly from the system variable 'join_buffer_size'.
When this flag is 'on' then the size of the buffer depends
on the estimated number of rows in the partial join whose
records are to be stored in the buffer.
By default this flag is set 'on'.
- Let "mysqld --help --verbose" list all optimizer options
- Make it possible to add new @@optimizer_switch flags w/o causing .result
changes all over the testsuite:
= Remove "select @@optimizer_switch" from tests that do not need all switches
= Move @@optimizer_switch-specific tests to t/optimizer_switch.test
