Lucene and Solr’s CheckIndex to the Rescue! by Rafał Kuć.
From the post:
While using Lucene and Solr we are used to a very high reliability. However, there may come a day when Solr will inform us that our index is corrupted, and we need to do something about it. Is the only way to repair the index to restore it from the backup or do full indexation? No – there is hope in the form of CheckIndex tool.
What is CheckIndex ?
CheckIndex is a tool available in the Lucene library, which allows you to check the files and create new segments that do not contain problematic entries. This means that this tool, with little loss of data is able to repair a broken index, and thus save us from having to restore the index from the backup (of course if we have it) or do the full indexing of all documents that were stored in Solr.
The question about when the last backup was run at the end of the article isn’t meant to be funny.
When I was training to be a NetWare sysadmin, more than a little while ago, one of the manuals advised that the #1 reason for sysadmins being fired was failure to maintain proper backups. I suspect that is probably still the case. Or at least I hope it is. There really is no excuse for failing to maintain proper backups.