> Does anyone have a feeling on whether
LUCENE-565 will improve performance?
Probably not much, if at all. Deletions happen after a segment flush, which is slightly less efficient (more indexreaders that need to be opened), but does get deletions in the index faster (meaning they are more likely to be "squeezed" out by a subsequent segment merge).
One small advantage to
LUCENE-565 is that overwriting is atomic... you can't crash and see duplicates.
The patch has been changed around multiple times, and it would now be necessary to include a lucene package in solr to get access to package-protected stuff that would allow efficient delete-by-query.