presto-orc/src/main/java/io/prestosql/orc/writer/SliceDictionaryColumnWriter.java/SliceDictionaryColumnWriter/getColumnEncodings
class SliceDictionaryColumnWriter:    @Override
    public Map<OrcColumnId, ColumnEncoding> getColumnEncodings()
    {
        checkState(closed);
        if (directEncoded) {
            return directColumnWriter.getColumnEncodings();
        }
        return ImmutableMap.of(columnId, columnEncoding);
    }