Adding ICU collation based sorting for facets

[jprante]

Hi,

I have implemented an ICU term facet that allows sorting the term entries by ICU collation rules. It is useful for linguistic applications. An example for german phonebook sorting is included.

Cheers, Jörg

[jprante]

I wonder how I can implement ICU collation based facets using the aggregation framework of upcoming 1.0.

Is it still planned to add collation-key based comparators for string terms in the new aggregation framework?

See also comment
elastic/elasticsearch#3300 (comment)

Right now, only simple comparators are implemented, like org.elasticsearch.search.aggregations.bucket.terms.Terms.Order.TERM_ASC and org.elasticsearch.search.aggregations.bucket.terms.Terms.Order.TERM_DESC

How can I extend them?

[dadoonet]

@jpountz Do you think you can answer @jprante and if this is something we would like to have in elasticsearch 2.x?

Jörg, I'm closing this PR as it won't be merged. If you plan to do something around aggs, please open a PR agains elasticsearch repo which now holds this plugin.

Thanks!