Because the default build configuration of the server will remain
at -DWITH_INNODB_AHI=ON, we want to test the instrumentation.
We make and revert the test adjustments in separate commits on purpose,
so that this commit can be easily reverted later if the default
build configuration is changed to -DWITH_INNODB_AHI=OFF.
The InnoDB adaptive hash index is sometimes degrading the performance of
InnoDB, and it is sometimes disabled to get more consistent performance.
We should have a compile-time option to disable the adaptive hash index.
Let us introduce two options:
OPTION(WITH_INNODB_AHI "Include innodb_adaptive_hash_index" ON)
OPTION(WITH_INNODB_ROOT_GUESS "Cache index root block descriptors" ON)
where WITH_INNODB_AHI always implies WITH_INNODB_ROOT_GUESS.
As part of this change, the misleadingly named function
trx_search_latch_release_if_reserved(trx) will be replaced with the macro
trx_assert_no_search_latch(trx) that will be empty unless
BTR_CUR_HASH_ADAPT is defined (cmake -DWITH_INNODB_AHI=ON).
We will also remove the unused column
INFORMATION_SCHEMA.INNODB_TRX.TRX_ADAPTIVE_HASH_TIMEOUT.
In MariaDB Server 10.1, it used to reflect the value of
trx_t::search_latch_timeout which could be adjusted during
row_search_for_mysql(). In 10.2, there is no such field.
Other than the removal of the unused column TRX_ADAPTIVE_HASH_TIMEOUT,
this is an almost non-functional change to the server when using the
default build options.
Some tests are adjusted so that they will work with both
-DWITH_INNODB_AHI=ON and -DWITH_INNODB_AHI=OFF. The test
innodb.innodb_monitor has been renamed to innodb.monitor
in order to track MySQL 5.7, and the duplicate tests
sys_vars.innodb_monitor_* are removed.
