public FieldInvertedIndex(DataSchema schema) {
this.schema = schema;
for (String field : schema.getColumns()) {
final Map<String, Set<Integer>> e =
new TreeMap<String, Set<Integer>>(); // using tree map is important for range queries
fields.add(e);
}
}
// add fields on index
public void addDocument(String... fields) {
for (int i = 0; i < fields.length; i++) {
final DataType type = schema.getType(i);
String field = fields[i];
final Map<String, Set<Integer>> stringSetMap = this.fields.get(i);
if (type == DataType.DateYear) { // reformat field value for date year
field = field.split("-")[0];
}
Set<Integer> integers = stringSetMap.get(field);
if (integers == null) {
integers = new TreeSet<>();
}
integers.add(docPosition);
stringSetMap.put(field, integers);
}
docPosition++;
}