/**
* Prepare a document reconstructor.
*
* @param reader IndexReader to read from.
* @param fieldNames if non-null or not empty, data will be collected only from these fields,
* otherwise data will be collected from all fields
* @param numTerms total number of terms in the index, or -1 if unknown (will be calculated)
* @throws Exception
*/
public DocReconstructor(IndexReader reader, String[] fieldNames, int numTerms) throws Exception {
if (reader == null) {
throw new Exception("IndexReader cannot be null.");
}
this.reader = reader;
if (fieldNames == null || fieldNames.length == 0) {
// collect fieldNames
this.fieldNames = (String[]) reader.getFieldNames(FieldOption.ALL).toArray(new String[0]);
} else {
this.fieldNames = fieldNames;
}
if (numTerms == -1) {
Fields fields = MultiFields.getFields(reader);
numTerms = 0;
FieldsEnum fe = fields.iterator();
String fld = null;
while ((fld = fe.next()) != null) {
TermsEnum te = fe.terms();
while (te.next() != null) {
numTerms++;
}
}
this.numTerms = numTerms;
}
deleted = MultiFields.getDeletedDocs(reader);
}
