Add support for aggregation of type expression

[saketbairoliya2]

Getting above error when trying to use aggregation of type expression

[jbguerraz]

Hello @saketbairoliya2
Adding an aggregator is pretty straigth-forward, take a look here: https://github.com/grafadruid/go-druid/tree/master/builder/aggregation
basically add a case here https://github.com/grafadruid/go-druid/blob/master/builder/aggregation/aggregation.go#L40
and then provide the structure for expression like here for instance https://github.com/grafadruid/go-druid/blob/master/builder/aggregation/string_last.go
I didn't find any expression aggregator here https://druid.apache.org/docs/latest/querying/aggregations.html nor here https://druid.apache.org/docs/latest/development/extensions.html could you please point me to the aggregator documentation ?
Thank you!

[jbguerraz]

@saketbairoliya2 any news on that ? since I didn't find that aggregator, maybe we can close it ?

[AngryShamrock]

@jbguerraz This aggregation type doesn't seem to be documented, but it does exist. I've seen it generated by EXPLAIN PLAN FOR when using Druid SQL

Here's the list of properties it accepts, from the druid github