On May 10, 2004, at 11:02 PM, Glen Stampoultzis wrote:
Hi... I have a query screen where most of the fields search a regular
database but one field searches for text in the body of the document. You
could say the database holds metadata about the documents. Effectively this
means I have two separate queries going on - a lucene query and a database
query. These results need to be combined.
Anyone have any strategies for dealing with this? I'm wondering whether
it's better to replicate searchable fields in the lucene index. This means
being very careful that updates get done in two places so it is not ideal.
Beyond what the other responses on this thread have been, another option is to use a custom Filter which can narrow a Lucene query down based on external criteria. Wrap that with the caching filter wrapper if things don't change and this could be highly efficient for successive searches.
In CVS HEAD, there is a new FilteredQuery which could leverage any custom Filter you create and allow you to constrain a query clause by DB criteria.
I built a proof-of-concept one for the book, which looks like this:
public interface SpecialsAccessor {
String[] isbns();
}public class SpecialsFilter extends Filter {
private SpecialsAccessor accessor; public SpecialsFilter(SpecialsAccessor accessor) {
this.accessor = accessor;
} public BitSet bits(IndexReader reader) throws IOException {
BitSet bits = new BitSet(reader.maxDoc());String[] isbns = accessor.isbns();
int[] docs = new int[1];
int[] freqs = new int[1]; for (int i = 0; i < isbns.length; i++) {
String isbn = isbns[i];
if (isbn != null) {
TermDocs termDocs =
reader.termDocs(new Term("isbn", isbn));
int count = termDocs.read(docs, freqs);
if (count == 1) {
bits.set(docs[0]); }
}
}return bits; }
public String toString() {
return "SpecialsFilter";
}
}The implementation of SpecialsAccessor is left as an exercise for the reader :) (I implemented a Mock version as an example). Consider adapting something like this for your DB access, then wrap with the caching wrapper.
Erik
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