@Override
  public int size() {
    // must call getValuesSet() to get the correct size -- expensive.
    // this size must reflect the dropping of null values (invalid entries),
    // (but NOT the dropping of duplicates)
    return values.size();
  }
Getter for property modifiable. Since a QRegion as a collection represents an unmodifiable
facade on the values of this region, return false.

@return Value of property modifiable.
geode-core/src/main/java/org/apache/geode/cache/query/internal/QRegion.java