Deduplication of search result with custom with custom sort

[Dmitry Emets]

Hi,
I need to deduplicate search results by specific field and I have no idea
how to implement this properly.
I have tried grouping with setGroupDocsLimit(1) and it gives me expected
results, but has not very good performance.
I think that I need something like DiversifiedTopDocsCollector, but
suitable for collecting TopFieldDocs.
Is there any possibility to achieve deduplication with existing lucene
components, or do I need to implement my own DiversifiedTopFieldsCollector?