Search your beans with Lucene — Suggest

We have seen so far how to run a search query on whatever field you mapped. Anyone used to a search engine already knows the next step: autocomplete, so the index can help you find the right query.

Autocomplete lives in its own artefact:

<dependency>
  <groupId>org.apache.lucene</groupId>
  <artifactId>lucene-suggest</artifactId>
  <version>10.5.1</version>
</dependency>

A second Directory

AnalyzingInfixSuggester is not an IndexSearcher on the track index. It is a dictionary with its own Directory. Use the same analyzer as before so prefixes match how titles were tokenized:

Directory suggestionDirectory = new ByteBuffersDirectory();
AnalyzingInfixSuggester suggester = new AnalyzingInfixSuggester(
        suggestionDirectory, analyzer);
suggester.build(new TrackSuggestionInputIterator(tracks.values()));

Keep it next to the track writer, behind the same write lock as rebuild / upsert. Incremental delete on an infix suggester is awkward; for a few thousand beans, rebuild the dictionary after every mutation.

Type “club”

List<Lookup.LookupResult> matches =
        suggester.lookup("club", Set.of(), 10, true, true);
Lookup.LookupResult match = matches.get(0);
String text = match.key.toString();              
// "Club House"
String field = match.payload.utf8ToString();     
// "genre"
String highlight = match.highlightKey.toString(); 
// "<b>Club</b> House"

This means that the first suggestion is Club House coming from the genre field and could be presented to the user as:

Club House.

Filter with the suggestion

Selecting Club House (field = "genre") could then call your backend search API: /tracks?genre=Club House and update the UI to reflect the selected filter chip.

If you want suggestions to respect the current filter set, change the call:

List<Track> scoped = search.filter(corpus, "", filters, mustNots);
List<TrackSuggestion> hits = index.suggest(prefix, scoped);

filter(..., "", filters, mustNots) applies the chips already on, with an empty query string. suggest(prefix, scoped) then looks up only inside that subset — so club cannot propose a genre that those chips already excluded.