Plus or minus sign using Apache Solr When I enable Apache solr, everything works perfectly fine except for the following scenario.

When I do a keyword search using character - (minus symbol), or +, I get the error: 


  The Apache Solr search engine is not available. Please contact your site administrator.


Do you know why this happens?
You need to be using Apache Solr 3.1 and have the edismax plugin enabled to allow for these boolean operator queries. You should see this in your Solr logs as 'an unknown query type' error. This should be an option in the ApacheSolr Drupal module since this patch but if not (or if you're running Apache Solr 1.4.x) you can check out this ticket on the solr forum for instructions on how to patch your solr and solrconfig.xml to allow for edismax queries.