Prevent duplication of Solr query highlight fields parameters

That was caused by concurrent modifications (with addHighlightField()
function) to the same SolrQuery instance when requesting Solr on remote
peers in p2p search.

source/net/yacy/peers/Protocol.java

@@ -74,7 +74,6 @@ import org.apache.solr.common.SolrInputDocument;
 
 import net.yacy.migration;
 import net.yacy.cora.date.GenericFormatter;
-import net.yacy.cora.document.analysis.Classification;
 import net.yacy.cora.document.analysis.Classification.ContentDomain;
 import net.yacy.cora.document.encoding.ASCII;
 import net.yacy.cora.document.encoding.UTF8;
@@ -1021,8 +1020,6 @@ public final class Protocol {
         }
     }
 
-    private final static CollectionSchema[] snippetFields = new CollectionSchema[]{CollectionSchema.description_txt, CollectionSchema.h4_txt, CollectionSchema.h3_txt, CollectionSchema.h2_txt, CollectionSchema.h1_txt, CollectionSchema.text_t};
-    
     /**
      * A task dedicated to requesting a Solr instance
      */
@@ -1199,19 +1196,6 @@ public final class Protocol {
         solrQuery.setStart(offset);
         solrQuery.setRows(count);
         
-        // set highlighting query attributes
-        if (event.query.contentdom == Classification.ContentDomain.TEXT || event.query.contentdom == Classification.ContentDomain.ALL) {
-            solrQuery.setHighlight(true);
-            solrQuery.setHighlightFragsize(SearchEvent.SNIPPET_MAX_LENGTH);
-            //solrQuery.setHighlightRequireFieldMatch();
-            solrQuery.setHighlightSimplePost("</b>");
-            solrQuery.setHighlightSimplePre("<b>");
-            solrQuery.setHighlightSnippets(5);
-            for (CollectionSchema field: snippetFields) solrQuery.addHighlightField(field.getSolrFieldName());
-            //System.out.println("*** debug-query-highligh ***:" + ConcurrentLog.stackTrace());
-        } else {
-            solrQuery.setHighlight(false);
-        }
         boolean localsearch = target == null || target.equals(event.peers.mySeed());
         Map<String, ReversibleScoreMap<String>> facets = new HashMap<String, ReversibleScoreMap<String>>(event.query.facetfields.size());
         Map<String, LinkedHashSet<String>> snippets = new HashMap<String, LinkedHashSet<String>>(); // this will be a list of urlhash-snippet entries
@@ -1322,15 +1306,15 @@ public final class Protocol {
             }
             
             // evaluate snippets
-            Map<String, Map<String, List<String>>> rawsnippets = rsp[0].getHighlighting(); // a map from the urlhash to a map with key=field and value = list of snippets
+            final Map<String, Map<String, List<String>>> rawsnippets = rsp[0].getHighlighting(); // a map from the urlhash to a map with key=field and value = list of snippets
             if (rawsnippets != null) {
-                nextsnippet: for (Map.Entry<String, Map<String, List<String>>> re: rawsnippets.entrySet()) {
-                    Map<String, List<String>> rs = re.getValue();
-                    for (CollectionSchema field: snippetFields) {
-                        if (rs.containsKey(field.getSolrFieldName())) {
-                            List<String> s = rs.get(field.getSolrFieldName());
+                nextsnippet: for (final Map.Entry<String, Map<String, List<String>>> re: rawsnippets.entrySet()) {
+                    final Map<String, List<String>> rs = re.getValue();
+                    for (final String field: solrQuery.getHighlightFields()) {
+                        if (rs.containsKey(field)) {
+                            final List<String> s = rs.get(field);
                             if (s.size() > 0) {
-                                LinkedHashSet<String> ls = new LinkedHashSet<String>();
+                                final LinkedHashSet<String> ls = new LinkedHashSet<String>();
                                 ls.addAll(s);
                                 snippets.put(re.getKey(), ls);
                                 continue nextsnippet;

source/net/yacy/search/query/QueryParams.java

@@ -115,6 +115,9 @@ public final class QueryParams {
         //missing: namespace
     }
     
+    /** List of Solr fields used to extract text snippets when requesting the Solr index */
+    private final static CollectionSchema[] SOLR_SNIPPET_FIELDS = new CollectionSchema[]{CollectionSchema.description_txt, CollectionSchema.h4_txt, CollectionSchema.h3_txt, CollectionSchema.h2_txt, CollectionSchema.h1_txt, CollectionSchema.text_t};
+    
     public static final Bitfield empty_constraint    = new Bitfield(4, "AAAAAA");
     public static final Pattern catchall_pattern = Pattern.compile(".*");
 
@@ -635,6 +638,21 @@ public final class QueryParams {
         if (bq.length() > 0) params.setParam(DisMaxParams.BQ, bq.split("[\\r\\n]+")); // split on any sequence consisting of CR and/or LF
         if (bf.length() > 0) params.setParam("boost", bf); // a boost function extension, see http://wiki.apache.org/solr/ExtendedDisMax#bf_.28Boost_Function.2C_additive.29
         
+        // set highlighting query attributes
+        if (this.contentdom == Classification.ContentDomain.TEXT || this.contentdom == Classification.ContentDomain.ALL) {
+        	params.setHighlight(true);
+        	params.setHighlightFragsize(SearchEvent.SNIPPET_MAX_LENGTH);
+            //params.setHighlightRequireFieldMatch();
+        	params.setHighlightSimplePost("</b>");
+        	params.setHighlightSimplePre("<b>");
+        	params.setHighlightSnippets(5);
+            for (final CollectionSchema field: SOLR_SNIPPET_FIELDS) {
+            	params.addHighlightField(field.getSolrFieldName());
+            }
+        } else {
+            params.setHighlight(false);
+        }
+        
         // prepare result
         ConcurrentLog.info("Protocol", "SOLR QUERY: " + params.toString());
         this.cachedQuery = params;