Re: Equiv. to where in(ids)

[Robert Pohl]

Michael,

Thanks for clarification!

//Rob

Michael Garski wrote:

Rob,

It looks like you want to do a full text search of names, but with
results restricted to an arbitrary subset of the full corpus with the
subset containing a person's friends based on a match on user id.  Is
that a correct assessment?

There are a few ways to achieve this -

* BooleanQuery Approach
Use two clauses: one forthe 'DisplayName' field to match the text,
another with a BooleanQuery that is an OR of all of the potential user
ids.  This is fairly simple to construct, but if you have more than a
handful of user ids it will perform poorly.

One thing to note is that I would advise against a leading wildcard as
it is very heavy and will cause you to walk over _all_ of the terms in
the field - trailing wild card has a similar effect depending on how
many terms match the wild card.

* Terms Filter Approach
There is a filter in the Java contrib section called TermsFilter (under
contrib\queries\) which creates a filter from a list of terms.  There is
not an equivalent in the Lucene.Net contrib yet, however creating a .Net
version is fairly simple.  I've done something similar to that to
implement a similar use case, and the filter is used to filter the
results to just the user ids that match those in your criteria.  This is
fairly performant when coupled with an index schema with at least two
fields - one for the display name and the other for the user id - plus
any other data you may need to search.

Michael

-----Original Message-----

From: Robert Pohl [mailto:robba...@gmail.com] Sent: Tuesday, December 15, 2009 10:48 AM

To: lucene-net-user@incubator.apache.org
Subject: Equiv. to where in(ids)

Hi,

I'm constructing a query where I want to search for members that are
your friends (in a social network).
And I'm not sure how construct the search that look for a member name
which need to have an ID that is A or B or C.

I would do that in SQL like this:
select *from members where username like '%rob%' and ID in(select Id
from friends)

The problem:

The problem is that the query must match ALL ids. I want it to match ANY
id.

My code:

            String[] fields = searchQuery.Split(' ');

            QueryParser qp = new QueryParser("DisplayName", new
StandardAnalyzer());

            BooleanQuery query = new BooleanQuery();
            foreach (string s in fields)
            {
                query.Add(qp.Parse(s), BooleanClause.Occur.SHOULD);
            }

            if(memberIds != null) // List<int> with friend id's
            {
                foreach (int id in memberIds)
                {
                    QueryParser qp2 = new QueryParser("Id", new
StandardAnalyzer());
                    Query q2 = qp2.Parse(id.ToString());
                    qp2.SetDefaultOperator(QueryParser.Operator.OR);
                    BooleanClause bc = new BooleanClause(q2,
BooleanClause.Occur.MUST);
                    query.Add(bc);
                }


Thanks,
Rob