The search query service trims the search results according to the rights of the user who issues the query.
The problem I have is content query search (SharePoint Search Service 14: FullTextSqlQuery) works fine for local Administrator users but returns zero results for all other local SharePoint 2010 users (AD is not involved). These users can access and view all documents so there does not appear to be any security issues within SharePoint. However, the log file shows the search results are all security trimmed out of the final result; the log does not contain any explicit error messages. So there appears to be an inconsistency between SharePoint and the search index with respect to access permissions.
Can anyone suggest how to diagnose the problem?