Let's make this an insertion-ordered set so that all logically identical queries get assigned table abbreviations in the same order. This is mostly cosmetic, but has no significant cost.

src/java/com/samskivert/depot/impl/DepotTypes.java

@@ -61,7 +61,7 @@ public class DepotTypes
         PersistenceContext ctx, Collection<? extends QueryClause> clauses)
         throws DatabaseException
     {
-        Set<Class<? extends PersistentRecord>> classSet = Sets.newHashSet();
+        Set<Class<? extends PersistentRecord>> classSet = Sets.newLinkedHashSet();
         for (QueryClause clause : clauses) {
             if (clause != null) {
                 clause.addClasses(classSet);