Toggling compression for stored fields

[Vitaly Funstein]

Is it possible to have a mix of compressed and uncompressed documents
within a single index? That is, can I load an index created with Lucene 4.0
into 4.1 and defer the decision of whether or not to use
CompressingStoredFieldsFormat until a later time, or even go back and forth
between compressed and uncompressed codecs, if needed? I thought at first
the answer would be an unequivocal "no", but then how would one migrate
data from 4.0 to 4.1 without a full reindex?