typedef int (*bt_compare_fcn)(const DBT *, const DBT *);
Set the Btree key comparison function.
This comparison function must return an integer less than, equal to,
or greater than zero if the first key argument is considered to be
respectively less than, equal to, or greater than the second key argument.
The same comparison method must be used on a given tree every time it
The data and size fields of the Dbt are the only
fields that may be used for the purposes of this comparison.
If no comparison function is specified, the keys are compared lexically,
with shorter keys collating before longer keys.