Lucene Solr using complex filters

Question

I am currently having a problem with specifying filters for Lucene/Solr. Every solution I come up with breaks other solutions. Let me start with an example. Assume that we have the following 5 documents:

• doc1 = [type:Car, sold:false, owner:John]
• doc2 = [type:Bike, productID:1, owner:Brian]
• doc3 = [type:Car, sold:true, owner:Mike]
• doc4 = [type:Bike, productID:2, owner:Josh]
• doc5 = [type:Car, sold:false, owner:John]

So I need to construct the following filter queries:

1. Give me all documents of type:Car which has sold:false only and if it is a type that is different that Car, include in the result. So basically I want docs 1, 2, 4, 5 the only document I don't want is doc3 because it is has sold:true. To put it more precisely:

   for each document d in solr/lucene
   if d.type == Car {
       if d.sold == false, then add to result
       else ignore
   }
   else {
       add to result
   }
   return result
   

2. Filter in all documents that are of (type:Car and sold:false) or (type:Bike and productID:1). So for this I will get 1,2,5.

3. Get all documents that if the type:Car then get only with sold:false, otherwise get me documents from owners John, Brian, Josh. So for this query I should get 1, 2, 4, 5.

Note: You don't know all the types in the documents. Here it is obvious because of the small number of documents.

So my solutions were:

1. (-type:Car) OR ((type:Car) AND (sold:false). This works fine and as expected.
2. ((-type:Car) OR ((type:Car) AND (sold:false)) AND ((-type:Bike) OR ((type:Bike) AND (productID:1))). This solution does not work.
3. ((owner:John) OR (owner:Brian) OR (owner:Josh)) AND ((-type:Car) OR ((type:Car) AND (sold:false)). This does not work, I can make it work if I do I do this: ((owner:John) OR (owner:Brian) OR (owner:Josh)) AND ((version:* OR (-type:Car)) OR ((type:Car) AND (sold:false)). I don't understand how this works, because logically it should work, but Solr/Lucene somehow does something.

Answer 1

Okay, to get anything but a sold car, you could use -(type:Car sold:true).

This can be incorporated into the other queries, but you'll need to be careful with lonely negative queries like this. Lucene doesn't handle them well, generally speaking, and Solr has some odd gotchas as well. Particularly, A -B reads more like "get all A but forbid B" rather than "get all A and anything but B". Similar problem with A or -B, see this question for more.

To get around that, you'll need to surround the negative with an extra set of parentheses, to ensure it is understood by Solr to be a standalone negative query, like: (-(type:Car AND sold:true))

So:

1. -(type:Car AND sold:true) (This doesn't get the result you stated, but as per my comment, I don't really understand your stated results)

2. (type:Bike AND productID:1) (-(type:Car AND sold:true)) (You actually wrote this in the description of the problem!)

3. (-(type:Car AND sold:false)) owner:(John Brian Josh)

Answer 2

My advice is to use programmatic Lucene (that is, directly in Java using the Java Lucene API) rather than issuing text queries which will be interpreted. This will give you much more fine-grained control.

What you're going to want to do is construct a Lucene Filter Object using the QueryWrapperFilter API. A QueryWrapperFilter is a filter which takes a Lucene Query, and filters out any documents which do not match that query.

In order to use QueryWrapperFilter, you'll need to construct a Query which matches the terms you're interested in. The best way to do this is to use TermQuery:

TermQuery tq = new TermQuery(new Term("fieldname", "value"));

As you might have guessed, you'll want to replace "fieldname" with the name of a field, and "value" with a desired value. For example, from your example in the OP, you might want to do something like new Term("type", "Car").

This only matches a single term. You're going to need multiple TermQueries, and a way to combine them to create a single, larger query. The best way to do this is with BooleanQuery:

BooleanQuery bq = new BooleanQuery();
bq.add(tq, BooleanQuery.Occur.MUST);

You can call bq.add as many times as you want - once for each TermQuery that you have. The second argument specifies how strict the query is. It can specify that a sub-query MUST appear, SHOULD appear, or should NOT appear (these are the three values of the BooleanQuery.Occur enum).

After you've added each of the sub-queries, this BooleanQuery represents the full query which will match only the documents you ask for. However, it's still not a filter. We now need to feed it to QueryWrapperFilter, which will give us back a filter object:

QueryWrapperFilter qwf = new QueryWrapperFilter(bq);

That should do it. Then if you want to run queries over only the documents allowed through by that filter, you just take your new query (call it q) and your filter, and create a FilteredQuery:

FilteredQuery fq = new FilteredQuery(q, qwf);