1 files changed, 65 insertions, 25 deletions

diff --git a/container-search/src/main/java/com/yahoo/prelude/searcher/FieldCollapsingSearcher.java b/container-search/src/main/java/com/yahoo/prelude/searcher/FieldCollapsingSearcher.java
index 708c6de1212..0559bd808bc 100644
--- a/container-search/src/main/java/com/yahoo/prelude/searcher/FieldCollapsingSearcher.java
+++ b/container-search/src/main/java/com/yahoo/prelude/searcher/FieldCollapsingSearcher.java
@@ -6,18 +6,20 @@ import com.yahoo.component.chain.dependencies.After;
 import com.yahoo.component.chain.dependencies.Before;
 import com.yahoo.container.QrSearchersConfig;
 import com.yahoo.prelude.fastsearch.FastHit;
+import com.yahoo.processing.request.CompoundName;
 import com.yahoo.search.Query;
 import com.yahoo.search.Result;
 import com.yahoo.search.Searcher;
-import com.yahoo.processing.request.CompoundName;
+import com.yahoo.search.query.Properties;
 import com.yahoo.search.result.Hit;
 import com.yahoo.search.searchchain.Execution;
 import com.yahoo.search.searchchain.PhaseNames;
 
+import java.util.Arrays;
 import java.util.Map;
 
 /**
- * A searcher which does parametrized collapsing.
+ * A searcher which does parameterized collapsing.
  *
  * @author Steinar Knutsen
  */
@@ -30,12 +32,16 @@ public class FieldCollapsingSearcher extends Searcher {
     private static final CompoundName collapsesize = CompoundName.from("collapsesize");
     private static final CompoundName collapseSummaryName = CompoundName.from("collapse.summary");
 
+    /** Separator used for the fieldnames in collapsefield */
+    private static final String separator = ",";
+
     /** Maximum number of queries to send next searcher */
     private static final int maxQueries = 4;
 
     /**
      * The max number of hits that will be preserved per unique
-     * value of the collapsing parameter.
+     * value of the collapsing parameter,
+     * if no field-specific value is configured.
      */
     private int defaultCollapseSize;
 
@@ -85,11 +91,14 @@ public class FieldCollapsingSearcher extends Searcher {
      */
     @Override
     public Result search(com.yahoo.search.Query query, Execution execution) {
-        String collapseField = query.properties().getString(collapsefield);
+        String collapseFieldParam = query.properties().getString(collapsefield);
+
+        if (collapseFieldParam == null) return execution.search(query);
+
+        String[] collapseFields = collapseFieldParam.split(separator);
 
-        if (collapseField == null) return execution.search(query);
+        int globalCollapseSize = query.properties().getInteger(collapsesize, defaultCollapseSize);
 
-        int collapseSize = query.properties().getInteger(collapsesize, defaultCollapseSize);
         query.properties().set(collapse, "0");
 
         int hitsToRequest = query.getHits() != 0 ? (int) Math.ceil((query.getOffset() + query.getHits() + 1) * extraFactor) : 0;
@@ -103,12 +112,15 @@ public class FieldCollapsingSearcher extends Searcher {
         String collapseSummary = query.properties().getString(collapseSummaryName);
         String summaryClass = (collapseSummary == null)
                               ? query.getPresentation().getSummary() : collapseSummary;
-        query.trace("Collapsing by '" + collapseField + "' using summary '" + collapseSummary + "'", 2);
+        query.trace("Collapsing by '" + Arrays.toString(collapseFields) + "' using summary '" + collapseSummary + "'", 2);
 
         do {
             resultSource = search(query.clone(), execution, nextOffset, hitsToRequest);
             fill(resultSource, summaryClass, execution);
-            collapse(result, knownCollapses, resultSource, collapseField, collapseSize);
+
+            collapse(result, knownCollapses, resultSource,
+                collapseFields, query.properties(), globalCollapseSize
+            );
 
             hitsAfterCollapse = result.getHitCount();
             if (resultSource.getTotalHitCount() < (hitsToRequest + nextOffset)) {
@@ -143,35 +155,63 @@ public class FieldCollapsingSearcher extends Searcher {
 
     /**
      * Collapse logic. Preserves only maxHitsPerField hits
-     * for each unique value of the collapsing parameter.
+     * for each unique value of the collapsing parameters.
+     * Uses collapsefields sequentially.
      */
-    private void collapse(Result result, Map<String, Integer> knownCollapses,
-                          Result resultSource, String collapseField, int collapseSize) {
+    private void collapse(Result result, Map<String, Integer> knownCollapses, Result resultSource,
+                          String[] collapseFields, Properties queryProperties, int globalCollapseSize) {
+
         for (Hit unknownHit : resultSource.hits()) {
             if (!(unknownHit instanceof FastHit hit)) {
                 result.hits().add(unknownHit);
                 continue;
             }
-            Object peek = hit.getField(collapseField);
-            String collapseId = peek != null ? peek.toString() : null;
-            if (collapseId == null) {
-                result.hits().add(hit);
-                continue;
-            }
 
-            if (knownCollapses.containsKey(collapseId)) {
-                int numHitsThisField = knownCollapses.get(collapseId);
+            boolean addHit = true;
 
-                if (numHitsThisField < collapseSize) {
-                    result.hits().add(hit);
-                    ++numHitsThisField;
-                    knownCollapses.put(collapseId, numHitsThisField);
+            for (String collapseField : collapseFields) {
+
+                Object peek = hit.getField(collapseField);
+                String collapseId = peek != null ? peek.toString() : null;
+                if (collapseId == null) {
+                    continue;
+                }
+
+                // prepending the fieldname is necessary to distinguish between values in the different collapsefields
+                // @ cannot occur in fieldnames
+                String collapseKey = collapseField + "@" + collapseId;
+
+                if (knownCollapses.containsKey(collapseKey)) {
+                    int numHitsThisField = knownCollapses.get(collapseKey);
+                    int collapseSize = getCollapseSize(queryProperties, collapseField, globalCollapseSize);
+
+                    if (numHitsThisField < collapseSize) {
+                        ++numHitsThisField;
+                        knownCollapses.put(collapseKey, numHitsThisField);
+                    } else {
+                        addHit = false;
+                        // immediate return, so that following collapseFields do not record the fieldvalues of this hit
+                        // needed for sequential collapsing, otherwise later collapsefields would remove too many hits
+                        break;
+                    }
+                } else {
+                    knownCollapses.put(collapseKey, 1);
                 }
-            } else {
-                knownCollapses.put(collapseId, 1);
+            }
+
+            if (addHit) {
                 result.hits().add(hit);
             }
         }
     }
 
+    private int getCollapseSize(Properties properties, String fieldName, int globalCollapseSize) {
+        Integer fieldCollapseSize = properties.getInteger(collapsesize.append(fieldName));
+
+        if (fieldCollapseSize != null) {
+            return fieldCollapseSize;
+        }
+
+        return globalCollapseSize;
+    }
 }