presto-main/src/main/java/io/prestosql/operator/index/IndexLoader.java/IndexLoader/getIndexedDataForKeys
class IndexLoader:    public IndexedData getIndexedDataForKeys(int position, Page indexPage)
    {
        // Normalize the indexBlocks so that they only encompass the unloaded positions
        int totalPositions = indexPage.getPositionCount();
        int remainingPositions = totalPositions - position;
        return getIndexedDataForKeys(indexPage.getRegion(position, remainingPositions));
    }