Out of curiosity and for education purposes, is the Collector approach I
proposed wrong/inefficient? Or less efficient than the matches() API?
I'm thinking, if you want to both match/rank documents and as a side effect
know which fields matched, the Collector will perform better than
Weight.matches(), but I could be wrong.
Shai
On Mon, Jun 27, 2022 at 11:57 AM Dawid Weiss <dawid.we...@gmail.com> wrote:
> The matches API is awesome. Use it. You can also get a rough glimpse
> into a superset of fields potentially matching the query via:
>
> query.visit(
> new QueryVisitor() {
> @Override
> public boolean acceptField(String field) {
> affectedFields.add(field);
> return false;
> }
> });
>
>
> https://lucene.apache.org/core/9_2_0/core/org/apache/lucene/search/Query.html#visit(org.apache.lucene.search.QueryVisitor)
>
> I'd go with the Matches API though.
>
> Dawid
>
> On Mon, Jun 27, 2022 at 10:48 AM Alan Woodward <romseyg...@gmail.com>
> wrote:
> >
> > The Matches API will give you this information - it’s still likely to be
> fairly slow, but it’s a lot easier to use than trying to parse Explain
> output.
> >
> > Query q = ….;
> > Weight w = searcher.createWeight(searcher.rewrite(query),
> ScoreMode.COMPLETE_NO_SCORES, 1.0f);
> >
> > Matches m = w.matches(context, doc);
> > List<String> matchingFields = new ArrayList();
> > for (String field : m) {
> > matchingFields.add(field);
> > }
> >
> > Bear in mind that `matches` doesn’t maintain any state between calls, so
> calling it for every matching document is likely to be slow; for those
> cases Shai’s suggestion of using a Collector and examining low-level
> scorers will perform better, but it won’t work for every query type.
> >
> >
> > > On 25 Jun 2022, at 04:14, Yichen Sun <yiche...@bu.edu> wrote:
> > >
> > > Hello!
> > >
> > > I’m a MSCS student from BU and learning to use Lucene. Recently I try
> to output matched fields by one query. For example, for one document, there
> are 10 fields and 2 of them match the query. I want to get the name of
> these fields.
> > >
> > > I have tried using explain() method and getting description then
> regex. However it cost so much time.
> > >
> > > I wonder what is the efficient way to get the matched fields. Would
> you please offer some help? Thank you so much!
> > >
> > > Best regards,
> > > Yichen Sun
> >
> >
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