CODEWITHSUNDEEP
javaluceneupgrade
Vegeta
Vegeta

Reputation: 135

Lucene IndexReader upgrade

I'm trying to upgrade Lucene in my application from version 3.5.0 to 5.0.0. The application has this code:

IndexReader indexReader=IndexReader.open(index);
String[] fields = indexReader.getFieldNames(FieldOption.ALL).toArray(new String[0]);

I need the fieldNames so I use them in a MultiFieldQueryParser. How can I make the change to version 5.0.0 ?

Upvotes: 2

Views: 147

Answers (1)

femtoRgon
femtoRgon

Reputation: 33351

You can get field information from the reader using the LeafReader.getFieldInfos() method, and in turn, you can get the field name from FieldInfo.name:

public static String[] getFieldNames(IndexReader reader) {
    List<String> fieldNames = new ArrayList<String>();
    //For a simple reader over only one index, reader.leaves() should only  return one LeafReaderContext
    for (LeafReaderContext readerCtx : reader.leaves()) {
        FieldInfos fields = readerCtx.reader().getFieldInfos();
        for (FieldInfo field : fields) {
            //Check whether the field is indexed and searchable, perhaps?
            fieldNames.add(field.name);
        }
    }
    return fieldNames.toArray(new String[fieldNames.size()]); 
}

Note: It might worth considering using a catch-all field that contains all the content you want to search for, instead. This is a common, and quite useful, pattern (e.g. Elasticsearch does this by default, with their _all field)

Going that route, you can expect the index to become a bit larger, but it makes it simpler to use, and performance should be improved.

Upvotes: 2

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