With Alfresco 5.0, when modifying permissions on a node in a site, it happens that Solr4 indexes this node several times. It is because records primary key in Solr4 are composed with 3 values, and when changing permissions, one of this values changes. Then Solr doesn’t find an existing record for the modified node so it creates a new record.

On the following picture, I used the faceted search to perform a simple research with the keyword « bonner ». It says « 2 results found » but only one is shown. Then, if I go in the node browser and search « cm\:name:bonner » (as an fts-alfresco or lucene query) I find 2 folders « Bonner 2015 » at the same location.

This issue has been reported and a fix is explained here :
issues.alfresco.com/jira/browse/MNT-13767

The solution is to perform the FIX action in Solr4 by calling the following URL :
localhost:8080/solr4/admin/cores?action=FIX
or
localhost:8443/solr4/admin/cores?action=FIX with ssl and performing a full Solr reindexing like explained on this page :
docs.alfresco.com/5.0/tasks/solr-reindex.html