On 8/7/2013 3:33 AM, Daniel Collins wrote:
I had been running a Solr 4.3.0 index, which I upgraded to 4.4.0 (but
hadn't changed LuceneVersion, so it was still using the LUCENE_43 codec).
I then had to back-out and return to a 4.3 system, and got an error when it
tried to read the index.
Now, it was only a dev system, so not a problem, and normally I would use
restore a backup anyway, but shouldn't this work? If I haven't changed the
codec, then Solr 4.4 should be using the same code as 4.3, so the data
should be compatible, no?
Using an index from a newer version is never guaranteed, and usually
will NOT work. The luceneMatchVersion setting doesn't typically affect
index format, it usually affects how analysis and query parser
components work - so you can tell Solr to use buggy behavior from an
earlier release.
Unless you actually change aspects of the codec (postings format,
docvalues format, etc), Solr uses the Lucene codec defaults, which can
(and usually does) change from release to release.
Looking through the Lucene 4.4 CHANGES.txt file (not the Solr file),
LUCENE-4936 looks like a change to the DocValues format. I can't tell
from the description whether LUCENE-5035 is a format change or a change
in how Lucene handles sorting in memory. The evidence I can find
suggests that the format is still called Lucene42DocValuesFormat, but
apparently it doesn't work the same.
Thanks,
Shawn
