I've seen uniqueKey customized in a SolrCloud setting recently. I thought I recalled some discussion or issues/limitations with this. I've seen a regret of making it customizable[1], and I concur with the sentiment. Does anyone recall a custom uniqueKey posing problems? My search in JIRA didn't find much.
[1] https://issues.apache.org/jira/browse/SOLR-6822?focusedCommentId=14234868&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14234868 ~ David Smiley Apache Lucene/Solr Search Developer http://www.linkedin.com/in/davidwsmiley
