Question

I have created the following document:

var document = new Document();
document.Add(new Field("category", "foo", Field.Store.YES, Field.Index.NOT_ANALYZED));
...

I have approx 10M documents which belong to 8 distinct categories. I would like to get all distinct categories (get all documents and read a value of category field) by executing search query. Is that feasible?

Another approach is to create a list of categories at index rebuild and to write these values in database.

Any help would be greatly appreciated!

Answer 1

Check out the IndexReader.Terms() method.

If you give it an empty Term for a field, it will return a TermEnum containing all the terms for that field.

TermEnum terms = indexReader.Terms(new Term("category"));
// enumerate the terms