Fix livelock situation in QueryProcessor

[simantics/platform.git] / bundles / org.simantics.db.layer0 / src / org / simantics / db / layer0 / adapter / impl / EntityInstances.java

diff --git a/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/adapter/impl/EntityInstances.java b/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/adapter/impl/EntityInstances.java
index 93903fb9b2d4371e01f521eca67c55cc925d33bf..ffbec2f5e01ca88222926bb1c03848ed940d692a 100644 (file)
--- a/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/adapter/impl/EntityInstances.java
+++ b/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/adapter/impl/EntityInstances.java
@@ -185,15 +185,17 @@ public class EntityInstances implements Instances {
        CollectionSupport coll = graph.getService(CollectionSupport.class);
        
        THashSet<Resource> visited = new THashSet<>();
-       List<Resource> rec = findRec(graph, index, filter, visited);
+       List<Resource> rec_ = findRec(graph, index, filter, visited);
+       // We must not modify rec_!
+       List<Resource> rec = rec_;
        for(Resource global : Layer0Utils.listGlobalOntologies(graph)) {
                if(!visited.add(global)) continue;
                List<Resource> rs = graph.syncRequest(new QueryIndex(global, type, filter), TransientCacheListener.<List<Resource>>instance());
-               if(rec.isEmpty() && !rs.isEmpty()) {
-                       // TODO: rec could be an immutable empty list
-                       rec = new ArrayList<Resource>();
+               if(!rs.isEmpty()) {
+                   if(rec == rec_)
+                       rec = new ArrayList<>(rec);
+                rec.addAll(rs);
                }
-               rec.addAll(rs);
        }
        Collection<Resource> result = coll.asSortedList(rec);
        return result;