presto-hive/src/main/java/io/prestosql/plugin/hive/rcfile/RcFilePageSource.java/RcFilePageSource/createBlock
class RcFilePageSource:    private Block createBlock(int currentPageSize, int fieldId)
    {
        int hiveColumnIndex = hiveColumnIndexes[fieldId];

        return new LazyBlock(
                currentPageSize,
                new RcFileBlockLoader(hiveColumnIndex));
    }