Reindexing in Solr

Terminology

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1. Use the dataimport handler with SolrEntityProcessor.
2. Export the data using Solr queries, then reimport it after making sure it's in the correct format. You could use XML or CSV for this. This is not a trivial process. There is no process or program available from the Solr project for doing this. Here are some possible ideas:
   1. http://grokbase.com/t/lucene/solr-user/134p562kxs/export-index-and-re-index-xml
   2. http://www.jason-palmer.com/2011/05/how-to-reindex-a-solr-database/
   3. Recent versions of Solr have added a new export capability – the /export handler. This might prove useful.

Alternatives when a traditional reindex isn't possible

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This is the approach used by the Smithsonian a large and very well-known library organization for their Solr installation, because getting access to the source databases for the individual entities within the organization is very difficult. This way they can reindex the online Solr at any time without having to get special permission from all those entities. When they index new content, it goes into a copy of Solr configured for storage only, not in-depth searching. Their main Solr instance uses SolrEntityProcessor to import from the intermediate Solr servers, so they can always reindex.

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