Solr query results using *

Question

I want to provide for partial matching, so I am tacking on * to the end of search queries. What I've noticed is that a search query of gatorade will return 12 results whereas gatorade* returns 7. So * seems to be 1 or many as opposed to 0 or many ... how can I achieve this? Am I going about partial matching in Solr all wrong? Thanks.

Answer 1

From what I've read the wildcards only matched words with additional characters after the search term. "Gatorade*" would match Gatorades but not Gatorade itself. It appears there's been an update to Solr in version 3.6 that takes this into account by using the 'multiterm' field type instead of the 'text' field.

A better description is here:

http://bensch.be/the-solr-wildcard-problem-and-multiterm-solution

Answer 2

My guess is the missing matches are "Gatorade" (with a capital 'G'), and you have a lowercase filter on your field. The idea is that you have filters in your schema.xml that preprocess the input data, but wildcard queries do not use them; see this about how Solr deals with wildcard queries:

http://solr.pl/en/2010/12/20/wildcard-queries-and-how-solr-handles-them/ ("Solr and wildcard handling").

Answer 3

Another alternative is to use NGrams and TokenFilterFactories, specifically the EdgeNGramFilterFactory. .

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: Docum Docume Document Documents

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).

Answer 4

If you want a query to return all documents that match either a stemmed form of gatorade or words that begin with gatorade, you'll need to construct the query yourself: +(gatorade gatorade*). You could alternatively extend the SolrParser to do this, but that's more work.

Answer 5

First, I think Solr wildcards are better summarized by "0 or many" than "1 or many". I doubt that's the source of your problem. (For example, see the javadocs for WildcardQuery.)

Second, are you using stemming, because my first guess is that you're dealing with a stemming issue. Solr wildcards can behave kind of oddly with stemming. This is because wildcard expansion is based by searching through the list of terms stored in the inverted index; these terms are going to be in stemmed form (perhaps something like "gatorad"), rather than the words from the original source text (perhaps "gatorade" or "gatorades").

For example, suppose you have a stemmer that maps both "gatorade" and "gatorades" to the stem "gatorad". This means your inverted index will not contain either "gatorade" or "gatorades", only "gatorad". If you then issue the query gatorade*, Solr will walk the term index looking for all the stems beginning with "gatorade". But there are no such stems, so you won't get any matches. Similarly, if you searched gatorades*, Solr will look for all stems beginning with "gatorades". But there are no such stems, so you won't get any matches.

Third, for optimal help, I'd suggest posting some more information, in particular:

• Some particular query URLs you are submitting to Solr
• An excerpt from your schema.xml file. In particular, include A) the field elements for the fields you are having trouble with, and B) the field type definitions corresponding to those fields

Answer 6

so what I was looking for is to make the search term for 'gatorade' -> 'gatorade OR gatorade*' which will give me all the matches i'm looking for.