prevent overwrite of crawled or received full documents by (newer) metadata

To protect rich index data (full resource) from overwriting by metadata gathered during remote search,
the newly introduced "firstSeen" index is used to differentiate between full-resource-doc and metadata,
as a "firstSeen" entry is only added on store's of full-resource-docs (during crawl or remote search).

source/net/yacy/peers/Protocol.java

@@ -746,7 +746,11 @@ public final class Protocol {
         if (event.addResultsToLocalIndex) {
             for (URIMetadataNode entry : storeDocs) {
                 try {
+                    // firstSseen is set on access (crawl/index) to full resource,
+                    // on existing firstSeen prevent that metadata overwrite this rich data (this can be the case if crawldata has older loaddate as metadata)
+                    if (!event.query.getSegment().firstSeen().has(entry.hash())) { // TODO: cleanup firstSeen on document deletion from index
                         event.query.getSegment().fulltext().putMetadata(entry);
+                    }
                 } catch (final IOException e) {
                     ConcurrentLog.logException(e);
                 }
@@ -1111,14 +1115,14 @@ public final class Protocol {
 
             // passed all checks, store url
             if (!localsearch) {
-                event.query.getSegment().setFirstSeenTime(urlEntry.hash(), Math.min(urlEntry.moddate().getTime(), System.currentTimeMillis()));
-                
                 // put the remote documents to the local index. We must convert the solr document to a solr input document:
                 if (event.addResultsToLocalIndex) {
                     final SolrInputDocument sid = event.query.getSegment().fulltext().getDefaultConfiguration().toSolrInputDocument(doc);
 
                     // the input document stays untouched because it contains top-level cloned objects
-                    if (event.addResultsToLocalIndex) docs.add(sid);
+                    docs.add(sid);
+                    // will be stored to index, and is a full solr document, can be added to firstseen
+                    event.query.getSegment().setFirstSeenTime(urlEntry.hash(), Math.min(urlEntry.moddate().getTime(), System.currentTimeMillis()));
                 }
 
                 // after this conversion we can remove the largest and not used field text_t and synonyms_sxt from the document