presto-orc/src/main/java/io/prestosql/orc/writer/StructColumnWriter.java/StructColumnWriter/getColumnEncodings
class StructColumnWriter:    @Override
    public Map<OrcColumnId, ColumnEncoding> getColumnEncodings()
    {
        ImmutableMap.Builder<OrcColumnId, ColumnEncoding> encodings = ImmutableMap.builder();
        encodings.put(columnId, COLUMN_ENCODING);
        structFields.stream()
                .map(ColumnWriter::getColumnEncodings)
                .forEach(encodings::putAll);
        return encodings.build();
    }