如何在Lucene.NET中搜索Field.Index.NOT_ANALYZED字段？

Question

I am new to Lucene.NET. I am adding fields as

Field.Index.NOT_ANALYZED

in a Lucene document. There is one default field which is added in document as

Field.Index.ANALYZED

I have no difficulty in searching the default field; but when I search on a specific field then Lucene returns 0 document. However if I change,

Field.Index.NOT_ANALYZED

to

Field.Index.ANALYZED

then things work properly. I think there is something to do with Analyzer. Can any body guide me on how to search a Field.Index.NOT_ANALYZED field?

Here is how I am creating the query parser:

QueryParser parser = 
    new QueryParser(
        Version.LUCENE_30, 
        "content", 
        new StandardAnalyzer(Version.LUCENE_30));

Answer 1

ANALYZED just means that the value is passed through an Analyzer before being indexed, while NOT_ANALYZED means that the value will be indexed as-is. The later means that a value like "hello world" will be indexed as just exactly that, the string "hello world". However, the syntax for the QueryParser class parses spaces as a term-separator, creating two terms "hello" and "world".

You will be able to match the field if you created a var q = new TermQuery(new Term(field, "hello world")) instead of calling var q = queryParser.Parse(field, "hello world") .

Answer 2

The issue seems to be using search values that do not match literally the values currently indexed; in other words, trying to match document containing hello world with a search for Hello World . Since all your fields are marker as NOT_ANALYZED Lucene is not processing (using an analyzer/tokenizer) the terms; it is simply indexing as they are passed, storing a string like hello world as hello world . For a search to return a match on that document, the search term needs to be exactly

hello world 

and not , Hello World or hello world. or Hello . All of these searches will return zero matches. For Lucene, it would be like trying to search for the number 3 , and get a match for 2 or 4 (as illogical as it might sound).

This is why the use of NOT_ANALYZED is only recommended for ID-type fields where you want the search to return an exact match, not a list of related/similar field values.

The advantage of using ANALYZED is that the search becomes more intuitive and friendly. Indexing a value like hello world will break the term down into tokens (to provide for partial matches like hello or world or even ello ) and stored in all-lowercase to avoid mismatches due to different casing (like Hello World or hELLO ).