presto-orc/src/main/java/io/prestosql/orc/DictionaryCompressionOptimizer.java/DictionaryColumnManager/tryConvertToDirect
class DictionaryColumnManager:        OptionalInt tryConvertToDirect(int maxDirectBytes)
        {
            OptionalInt directBytes = dictionaryColumn.tryConvertToDirect(maxDirectBytes);
            if (directBytes.isPresent()) {
                directEncoded = true;
            }
            return directBytes;
        }