presto-orc/src/main/java/io/prestosql/orc/reader/StructColumnReader.java/StructColumnReader/startStripe
class StructColumnReader:    @Override
    public void startStripe(ZoneId timeZone, InputStreamSources dictionaryStreamSources, ColumnMetadata<ColumnEncoding> encoding)
            throws IOException
    {
        presentStreamSource = missingStreamSource(BooleanInputStream.class);

        readOffset = 0;
        nextBatchSize = 0;

        presentStream = null;

        rowGroupOpen = false;

        for (ColumnReader structField : structFields.values()) {
            structField.startStripe(timeZone, dictionaryStreamSources, encoding);
        }
    }