Change separator in FieldCollapsingSearcher

_ can occur in fieldnames, @ cannot

1 files changed, 2 insertions, 1 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 5d848bb2ad5..31542cb194d 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
@@ -182,7 +182,8 @@ public class FieldCollapsingSearcher extends Searcher {
             }
 
             // prepending the fieldname is necessary to distinguish between values in the different collapsefields
-            String collapseKey = collapseField + "_" + collapseId;
+            // @ cannot occur in fieldnames
+            String collapseKey = collapseField + "@" + collapseId;
 
             if (knownCollapses.containsKey(collapseKey)) {
                 int numHitsThisField = knownCollapses.get(collapseKey);