Lucene – Wildcards in phrases

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Problem :

I am currently attempting to use Lucene to search data populated in an index.

I can match on exact phrases by enclosing it in brackets (i.e. “Processing Documents”), but cannot get Lucene to find that phrase by doing any sort of “Processing Document*”.

The obvious difference being the wildcard at the end.

I am currently attempting to use Luke to view and search the index. (it drops the asterisk at the end of the phrase when parsing)

Adding the quotes around the data seems to be the main culprit as searching for document* will work, but “document*” does not

Any assistance would be greatly appreciated

Solution :

Lucene 2.9 has ComplexPhraseQueryParser which can handle wildcards in phrases.

What you’re looking for is FuzzyQuery which allows one to search for results with similar words based on Levenshtein distance. Alternatively you may also want to consider using slop of PhraseQuery (also available in MultiPhraseQuery) if the order of words isn’t significant.

Not only does the QueryParser not support wildcards in phrases, PhraseQuery itself only supports Terms. MultiPhraseQuery comes closer, but as its summary says, you still need to enumerate the IndexReader.terms yourself to match the wildcard.

It seems that the default QueryParser cannot handle this. You can probably create a custom QueryParser for wildcards in phrases. If your example is representative, stemming may solve your problem. Please read the documentation for PorterStemFilter to see whether it fits.

Another alternative is to use NGrams and specifically the EdgeNGram.

This will create indexes for ngrams or parts of words.
Documents, with a min ngram size of 5 and max ngram size of 8, would index:

There is a bit of a tradeoff for index size and time.
One of the Solr books quotes as a rough guide:
Indexing takes 10 times longer
Uses 5 times more disk space
Creates 6 times more distinct terms.

However, the EdgeNGram will do better than that.

You do need to make sure that you don’t submit wildcard character in your queries.
As you aren’t doing a wildcard search, you are matching a search term on ngrams(parts of words).

I was also looking for the same thing and what i found is PrefixQuery gives u a combination of some thing like this “Processing Document*”.But the thing is your field which you are searching for should be untokenized and store it in lowercase (reason for so since it is untokenized indexer wont save your field values in lowercase) for this to work.Here is code for PrefixQuery which worked for me :-

List<SearchResult> results = new List<SearchResult>();
Lucene.Net.Store.Directory searchDir = FSDirectory.GetDirectory(this._indexLocation, false);
IndexSearcher searcher = new IndexSearcher( searchDir );
Hits hits;

BooleanQuery query = new BooleanQuery();
query.Add(new PrefixQuery(new Term(FILE_NAME_KEY, keyWords.ToLower())), BooleanClause.Occur.MUST);
hits = searcher.Search(query);
this.FillResults(hits, results);

Use a SpanNearQuery with a slop of 0.

Unfortunately there’s no SpanWildcardQuery in Lucene.Net. Either you’ll need to use SpanMultiTermQueryWrapper, or with little effort you can convert the java version to C#.

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