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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