Add a uniqueMsLevels method which can be used to implement more
efficient (backend-specific) implementations to get the unique MS levels from
a data set. The default implementation uses unique(msLevel(object)), which
can however be very slow, because it requires retrieving all MS levels from
the backend. Database-backed backends could use dedicated SQL queries to speed
that up.
Use the uniqueMsLevels function by default in all methods that have a
msLevels. parameter.
uniqueMsLevels
method which can be used to implement more efficient (backend-specific) implementations to get the unique MS levels from a data set. The default implementation usesunique(msLevel(object))
, which can however be very slow, because it requires retrieving all MS levels from the backend. Database-backed backends could use dedicated SQL queries to speed that up.uniqueMsLevels
function by default in all methods that have amsLevels.
parameter.