Thank you Shawn. This was detailed and very helpful. Skand.
On May 7, 2013, at 5:54 PM, Shawn Heisey <s...@elyograg.org> wrote: > On 5/7/2013 3:11 PM, Skand Gupta wrote: >> We have a fairly large (in the order of 10s of TB) indices built using Solr >> 3.5. We are considering migrating to Solr 4.3 and was wondering what the >> policy is on maintaining backward compatibility of the indices? Will 4.3 >> work with my 3.5 indexes? Because of the large data size, I would ideally >> like to move new data to 4.3 and gradually re-index all the 3.5 indices. > > Solr 4.x will read 3.x indexes with no problem. When Solr 5.x comes out, it > will read 4.x indexes, but it will not read 3.x indexes. > > If the 4.x server does any updates on a 3.x index, it will write new segments > in the new format, and if existing segments get merged, they will be in the > new format. > > If you do an optimize in that situation, which would take forever with > terabytes of data, Solr would convert the index format. Reindexing is MUCH > better, but you've already stated that as a goal, so I won't mention any more > about that. > > Due to advances and bugfixes, you might see some unusual behavior until you > reindex. This happens due to changes in the way analyzers and query parsers > work as compared to the way things worked on 3.5 when you built the index. > The more complicated your analyzer chains are in your schema, the more likely > you are to run into this. > > One thing that might be of immediate concern - in 4.0 and later, the forward > slash is a special query character and must be escaped with a backslash. It > is safe to send this escaped character to 3.5 as well. The utility method in > SolrJ for escaping queries (ClientUtils#escapeQueryChars) has been updated to > include the foward slash in newer SolrJ versions. > > Thanks, > Shawn >
