Given an existing index, is there any way to update the value of a particular
field across all documents, without deleting/re-indexing documents? For
instance, if I have a date field, and I need to offset all dates based on
change to stored time zone (subtract 12 hours from each value). The sort order
of field values would not change, and the postings should not need to change,
only values of fields. I do not believe there is any API to do it, but is
there some lower level way to do it (modifying files manually)? I only ask
because I have a large index and I don't want to re-index all documents.
