Hi again, I think I can understand how to write the descriptor in the packages: org.apache.asterix.runtime.aggregates.std and org.apache.asterix.runtime.aggregates.scalar. But I am not sure I understand how to write the descriptor in the package: org.apache.asterix.runtime.aggregates.serializable.std because it requires setting a state in the init function that doesn't seem to have a pattern in the other descriptors. Also I don't seem to understand the reasons for implementing each of these descriptors for the aggregate functions.
On 17 July 2017 at 16:56, Riyafa Abdul Hameed <[email protected]> wrote: > Hi all, > > I meant any explanation on the implementation of aggregate functions in > AsterixDB would be highly appreciated. > > Thank you. > Yours sincerely, > Riyafa > > On 16 July 2017 at 08:01, Riyafa Abdul Hameed <[email protected]> wrote: > >> Dear all, >> >> I am trying to create aggregate functions and I see there are more than >> one function descriptors for one single function. >> For example the function array_count(collection) has the following >> descriptors: >> >> >> - ScalarCountAggregateDescriptor >> - SerializableCountAggregateDescriptor >> - CountAggregateDescriptor >> >> I am not sure I understand the difference between each of this. Can you >> please provide and example or point me to a documentation entry to learn >> how to properly implement aggregate functions? >> >> The function I am trying to implement is ST_Extent. >> <https://postgis.net/docs/manual-1.4/ST_Extent.html> >> >> Thank you. >> >> Yours sincerely, >> >> Riyafa >> > > > > -- > Riyafa Abdul Hameed > Undergraduate, University of Moratuwa > > Email: [email protected] > Website: https://riyafa.wordpress.com/ <http://riyafa.wordpress.com/> > <http://facebook.com/riyafa.ahf> <http://lk.linkedin.com/in/riyafa> > <http://twitter.com/Riyafa1> >
