Migrate data from Solr 3

Question

I'm thinking about migrating from Solr 3 to Solrcloud or Elasticsearch and was wondering if is it possible to import data indexed with Solr 3.x to Solrcloud (solr 4) and/or Elasticsearch?

They're all lucene based, but since they have different behaviors I'm not really sure that it will work.

Has anyone ever done this? How it going? Related issues?

Answer 1

Regarding importing data from solr to elasticsearch you can take a look at the elasticsearch mock solr plugin. It adds a new solr-alike endpoint to elasticsearch, so that you can use the indexer that you've written for solr (if you have one) to index documents in elasticsearch.

Also, I've been working on an elasticsearch solr river which would allow to import data from solr to elasticsearch through the solrj library. The only limitation is that it can import only the fields that you configured as stored in solr. I should be able to make it public pretty soon, just a matter of days. I'll update my answer as soon as it's available.

Regarding the upgrade of Solr from 3.x to 4.0, not a big deal. The index format has changed, but Solr will take care of upgrading the index. That happens automatically once you start Solr with your old index. But after that the index cannot be read anymore by a previous Solr/lucene version. If you have a master/slave setup you should upgrade the slaves first, otherwise the index on the master would be replicated to the slaves which cannot read it yet.

UPDATE
Regarding the river that I mentioned: I made it public, you can download it from my github profile: https://github.com/javanna/elasticsearch-river-solr.