- add canonical field only if requested by solr schema

- remove canonical url from in/outbound urls if present

source/net/yacy/search/index/SolrConfiguration.java

@@ -195,9 +195,6 @@ public class SolrConfiguration extends ConfigurationSet implements Serializable
 
             addSolr(solrdoc, SolrField.htags_i, h);
 
-            // canonical tag
-            if (html.getCanonical() != null) addSolr(solrdoc, SolrField.canonical_s, html.getCanonical().toNormalform(false, false));
-
             // noindex and nofollow attributes
             // from HTML (meta-tag in HTML header: robots)
             // and HTTP header (x-robots property)
@@ -343,6 +340,16 @@ public class SolrConfiguration extends ConfigurationSet implements Serializable
                 if (iframes.length > 0) addSolr(solrdoc, SolrField.iframes_txt, iframes);
             }
 
+            // canonical tag
+            if (isEmpty() || contains(SolrField.canonical_s.name())) {
+                final MultiProtocolURI canonical = html.getCanonical();
+                if (canonical != null) {
+                    inboundLinks.remove(canonical);
+                    ouboundLinks.remove(canonical);
+                    addSolr(solrdoc, SolrField.canonical_s, canonical.toNormalform(false, false));
+                }
+            }
+
             // flash embedded
             if (isEmpty() || contains(SolrField.flash_b.name())) {
                 MultiProtocolURI[] flashURLs = html.getFlash();