How do I sort Lucene results by field value using a HitCollector?

Question

I'm using the following code to execute a query in Lucene.Net

var collector = new GroupingHitCollector(searcher.GetIndexReader());
searcher.Search(myQuery, collector);
resultsCount = collector.Hits.Count;

How do I sort these search results based on a field?

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Update

Thanks for your answer. I had tried using TopFieldDocCollector but I got an error saying, "value is too small or too large" when i passed 5000 as numHits argument value. Please suggest a valid value to pass.

Solution

The search.Searcher.search method will accept a search.Sort parameter, which can be constructed as simply as:

new Sort("my_sort_field")

However, there are some limitations on which fields can be sorted on - they need to be indexed but not tokenized, and the values convertible to Strings, Floats or Integers.

Lucene in Action covers all of the details, as well as sorting by multiple fields and so on.

Comments

[James Brady]

...and not tokenized - beat me to it :)

[Ed.]

thanks for your answer......... I had tried using TopFieldDocCollector but i got an error saying "value is too small or too large" when i passed 5000 as numHits argument value...please suggest a valid value to pass...

[Hakanai]

"No user in an interactive application is going to want to see that many" is a bit presumptuous. Users scream and complain even when we truncate to 200,000 for legitimate technical reasons...

[Scott Simontis]

@janwen According to the docs for Lucene, it is not required that the value be stored, only indexed