Solr reindex after schema change

Question

I need to change the datatype of one field from "int" to "long" because some of the values exceed the upper limit of 32-bit signed integer. I might also need to add and drop some fields in the future. Will my index be updated automatically after uploading the new schema.xml? If no, how should I go about re-indexing?

The Solr FAQ suggests that I remove the data via an update command that deletes all data. However, my team is using Cassandra as the primary database and it seems that Cassandra and Solr are tightly coupled (i.e. whatever you do in your Solr index will directly affect the Cassandra data). In our case, deleting the data in Solr results to the deletion of the underlying Cassandra row. What is the best approach to deal with this? The Cassandra table (and Solr core) contains more than 2 billion rows so creating a duplicate core and swapping the two afterwards is not practical.

Note: We are using Datastax Enterprise 4.0. I'm not sure if the behavior I described above is the true for the open-source Solr

Answer 1

You need to reindex the Solr data. Unfortunately, since you are changing the type of a field, you need to delete the old index data for Solr first, and then reindex from the Cassandra data.

See page 109 of the PDF for the DSE 4.0 doc for instructions for Full Reindex from the Solr Admin UI, or page 126 for Solr reload and full reindex from the command line (curl command) - using the reindex=true and deleteAll=true parameters.