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diff --git a/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/wrapper/SingleFunctionalOrNullProcedure.java b/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/wrapper/SingleFunctionalOrNullProcedure.java
new file mode 100644
index 000000000..e593dafb3
--- /dev/null
+++ b/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/wrapper/SingleFunctionalOrNullProcedure.java
@@ -0,0 +1,76 @@
+/*******************************************************************************
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management
+ * in Industry THTH ry.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     VTT Technical Research Centre of Finland - initial API and implementation
+ *******************************************************************************/
+package org.simantics.db.common.procedure.single.wrapper;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.simantics.db.AsyncReadGraph;
+import org.simantics.db.common.procedure.adapter.AsyncMultiProcedureAdapter;
+import org.simantics.db.exception.ManyObjectsForFunctionalRelationException;
+import org.simantics.db.procedure.AsyncProcedure;
+
+final public class SingleFunctionalOrNullProcedure<Result> extends AsyncMultiProcedureAdapter<Result> {
+    
+	final String location;
+	final AsyncProcedure<Result> procedure;
+    final AtomicBoolean found = new AtomicBoolean(false);
+    final AtomicBoolean guard = new AtomicBoolean(false);
+    final AtomicBoolean exception = new AtomicBoolean(false);
+    
+    public SingleFunctionalOrNullProcedure(String location, AsyncProcedure<Result> procedure) {
+        
+    	this.location = location;
+        this.procedure = procedure;
+        
+    }
+    
+    @Override
+    public void execute(AsyncReadGraph graph, Result result) {
+        
+        assert(!guard.get());
+
+        if(found.compareAndSet(false, true)) {
+            procedure.execute(graph, result);
+        } else {
+            if(exception.compareAndSet(false, true)) {
+                procedure.exception(graph, new ManyObjectsForFunctionalRelationException(location + " -> " + procedure));
+            }
+        }
+        
+    }
+	
+    @Override
+    public void finished(AsyncReadGraph graph) {
+
+        assert(!guard.get());
+        
+        guard.set(true);
+        
+        if(found.compareAndSet(false, true)) {
+            procedure.execute(graph, null);
+        }
+        
+    }
+    
+    @Override
+    public void exception(AsyncReadGraph graph, Throwable t) {
+        
+        procedure.exception(graph, t);
+        
+    }
+    
+    @Override
+    public String toString() {
+        return "SingleFunctionalOrNullProcedure -> " + procedure;
+    }
+
+}