Question

We use Lucene.NET to implement a full text search on a clients website. The search itself works already but we now want to implement a modification.

Currently all terms get appended a * which leads Lucene to perform what I would classify as a StartsWith search.

In the future we would like to have a search that performs something like a Contains rather than a StartsWith.

We use

• Lucene.Net 2.9.2.2
• StandardAnalyzer
• default QueryParser

Samples:

(Title:Orch*) matches: Orchestra

but:

(Title:rch*) does not match: Orchestra

We want the first and the second one to both match Orchestra.

Basically I want the exact opposite of what was asked in this question, I’m not sure why for this person Lucene performed a Contains and rather than a StartsWith by default:
Why is this Lucene query a "contains" instead of a "startsWith"?

How can we make this happen?
I have the feeling it has something to do with the Analyzer but I’m not sure.

Answer 1

First off, I assume you’re using StandardAnalyzer, or something similar. Your linked question fail to understand that you search for terms, and his case a* will match “Fleet Africa” because it’s tokenized into “fleet” and “africa”.

You need to call QueryParser.SetAllowLeadingWildcard(true) to be able to write queries like field:*value*. Are you actually changing the string that’s passed to QueryParser?

You could parse the query as usual, and then implement a QueryVisitor that rewrites all TermQuery into WildcardQuery. That way you still support phrase searches.

I see no good things in rewriting queries into prefix- or wildcard-queries. There is very little shared between an orc, or a chest, and an Orchestra, but both words will match. Instead, hook up your customer with an analyzer that supports stemming, synonyms, and provide a spell correction feature to fix simple searching mistakes.