Let's have another go at this

d2rq-self-joins2.patch

diff --git a/src/de/fuberlin/wiwiss/d2rq/engine/TripleRelationJoiner.java b/src/de/fuberlin/wiwiss/d2rq/engine/TripleRelationJoiner.java
index e9efd77..3211078 100644
--- a/src/de/fuberlin/wiwiss/d2rq/engine/TripleRelationJoiner.java
+++ b/src/de/fuberlin/wiwiss/d2rq/engine/TripleRelationJoiner.java
@@ -67,9 +67,20 @@ class TripleRelationJoiner {
                        Set<String> attributeNames)
        {
                Map<String,List<String>> uniqueKeys = database.getUniqueKeyColumns(originalName);
-               if (uniqueKeys == null) return false;
+               if (uniqueKeys != null) {
                for (List<String> indexColumns: uniqueKeys.values()) {
-                       if (attributeNames.containsAll(indexColumns)) return true;
+                               if (attributeNames.containsAll(indexColumns)) {
+                                       return true;
+                               }
+                       }
+               }
+               List<Attribute> primaryKeys = database.schemaInspector().primaryKeyColumns(originalName);
+               if (primaryKeys != null) {
+                       for (Attribute attr: primaryKeys) {
+                               if (!attributeNames.contains(attr.attributeName()))
+                                       return false;
+                       }
+                       return true;
                }
                return false;
        }
@@ -163,17 +174,17 @@ class TripleRelationJoiner {
                                        names.add(t.getObject().getName());
        
                                for (String name: names) {
-                                       NodeMaker n = (NodeMaker) nodeSets.toMap().get(name);
+                                       Var nameVar = Var.alloc(name);
+                                       NodeMaker n = (NodeMaker) nodeSets.toMap().get(nameVar);
                                        if (n != null/* && n instanceof TypedNodeMaker*/) {
-
                                                AttributeSet attributes = AttributeSet.createFrom(n);
                                                /*
                                                 * If we would set an alias to this table...
                                                 */
                                                if (attributes != null) {
-                                                       RelationName originalName = ((AliasMap)nodeSets.relationAliases().get(name)).origina
+                                                       AliasMap amap = (AliasMap)(nodeSets.relationAliases().get(nameVar));
+                                                       RelationName originalName = amap.originalOf(attributes.relationName);
                                                        if (r.baseRelation().aliases().hasAlias(originalName)) { 
-
                                                                /*
                                                                 * ... and indexes are in place to guarantee uniqueness of the attribute com
                                                                 */