Robert Stewart wrote:
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.
Perhaps you could do this using FilterIndexReader implementation, i.e. wrap your original index within this filter and then invoke IndexWriter.addIndexes(IndexReader[]). If you override FilterIndexReader.document(int, FieldSelector), which retrieves the stored fields of a document, then you can change the values of stored fields only, just before they are added to the new index. Note that this works ONLY for non-indexed fields that are stored (i.e. Store.YES, Index.NO) - if a field is both stored and indexed then you need to modify the postings too, which requires overriding other methods.
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