enhanced exists()-method for solr; should reduce a lot of IO during DHT

target selection

source/net/yacy/cora/federate/solr/connector/AbstractSolrConnector.java

@@ -62,10 +62,6 @@ public abstract class AbstractSolrConnector implements SolrConnector {
     public boolean exists(final String fieldName, final String key) throws IOException {
         if (fieldName == null) return false;
         try {
-            if (fieldName.equals(YaCySchema.id.getSolrFieldName())) {
-                final SolrDocument doc = getById(key, fieldName);
-                return doc != null;
-            }
             long count = getQueryCount(fieldName + ":\"" + key + "\"");
             return count > 0;
         } catch (final Throwable e) {

source/net/yacy/cora/federate/solr/connector/SolrServerConnector.java

@@ -324,7 +324,7 @@ public abstract class SolrServerConnector extends AbstractSolrConnector implemen
         params.setRows(0);
         params.setStart(0);
         params.setFacet(false);
-        params.setFields(YaCySchema.id.getSolrFieldName());
+        //params.setFields(YaCySchema.id.getSolrFieldName());
 
         // query the server
         QueryResponse rsp = query(params);