Phrase query in Lucene 6.2.0 - mongodb

Question

I have a document like this:
{
"_id" : ObjectId("586b723b4b9a835db416fa26"),
"name" : "test",
"countries" : {
"country" : [
{
"name" : "russia iraq"
},
{
"name" : "USA china"
}
]
}
}
In MongoDB I am trying to retrieve it using phrase query(Lucene 6.2.0). My code looks as folllows:
StandardAnalyzer analyzer = new StandardAnalyzer();
// 1. create the index
Directory index = new RAMDirectory();
IndexWriterConfig config = new IndexWriterConfig(analyzer);
try {
IndexWriter w = new IndexWriter(index, config);
MongoClient client = new MongoClient("localhost", 27017);
DB database = client.getDB("test123");
DBCollection coll = database.getCollection("test1");
//MongoCollection<org.bson.Document> collection = database.getCollection("test1");
DBCursor cursor = coll.find();
System.out.println(cursor);
while (cursor.hasNext()) {
BasicDBObject obj = (BasicDBObject) cursor.next();
Document doc = new Document();
BasicDBObject f = (BasicDBObject) (obj.get("countries"));
List<BasicDBObject> dts = (List<BasicDBObject>)(f.get("country"));
doc.add(new TextField("id",obj.get("_id").toString().toLowerCase(), Field.Store.YES));
doc.add(new StringField("name",obj.get("name").toString(), Field.Store.YES));
doc.add(new StringField("countries",f.toString(), Field.Store.YES));
for(BasicDBObject d : dts){
doc.add(new StringField("country",d.get("name").toString(), Field.Store.YES));
//
}
w.addDocument(doc);
}
w.close();
and my search goes like :
PhraseQuery query = new PhraseQuery("country", "iraq russia" );
// 3. search
int hitsPerPage = 10;
IndexReader reader = DirectoryReader.open(index);
IndexSearcher searcher = new IndexSearcher(reader);
TopDocs docs = searcher.search(query, hitsPerPage);
ScoreDoc[] hits = docs.scoreDocs;
// 4. display results
System.out.println("Found " + hits.length + " hits.");
for(int j=0;j<hits.length;++j) {
int docId = hits[j].doc;
Document d = searcher.doc(docId);
System.out.println(d);
}
reader.close();
}
catch (Exception e) {
e.printStackTrace();
}
I am getting zero hits for this query. Can anyone tell what I am doing wrong?
jars used:
lucene-queries4.2.0
lucene-queryparser-6.2.1
lucene-analyzers-common-6.2.0

Answer 1

i made certain changes which goes like:
Query query = new PhraseQuery.Builder()
.add(new Term("country", "iraq"))
.add(new Term("country", "russia"))
.setSlop(2)
.build();
and also i changed the type of feild while indexing :
for(BasicDBObject d : dts){
doc.add(newTextField("country",d.get("name").toString(), Field.Store.YES));
}
But can anyone tell me the difference between StringFeild and TextFeild while indexing?

Answer 2

Firstly, never mix Lucene versions. All your jars should be the same version. Upgrade lucene-queries to 6.2.1. In practice you might or might not run into trouble mixing up 6.2.0 and 6.2.1, but you definitely should upgrade lucene-analyzers-common as well.
PhraseQuery doesn't analyze for you, you have to add terms to it separately. In your example, "iraq russia" is treated as a single terms, rather than two separate (analyzed) terms.
It should look something like this:
Query query = new PhraseQuery.Builder()
.add(new Term("country", "iraq"))
.add(new Term("country", "russia"))
.build();
If you want something that will analyze for you, you can use the QueryParser:
QueryParser parser = new QueryParser("country", new StandardAnalyzer())
Query query = queryparser.parse("\"iraq russia\"");