We need Key to export a Key.Expression which we can use inside the SQL for a

KeySet so that the "where" keyword is not repeated every time we bind a key.

src/java/com/samskivert/jdbc/depot/BindVisitor.java

@@ -71,7 +71,7 @@ public class BindVisitor implements ExpressionVisitor
         // nothing needed
     }
 
-    public void visit (Key<? extends PersistentRecord> key)
+    public void visit (Key<? extends PersistentRecord>.Expression key)
     {
         for (Comparable<?> value : key.getValues()) {
             if (value != null) {

src/java/com/samskivert/jdbc/depot/BuildVisitor.java

@@ -94,9 +94,8 @@ public abstract class BuildVisitor implements ExpressionVisitor
         where.getWhereExpression().accept(this);
     }
 
-    public void visit (Key<? extends PersistentRecord> key)
+    public void visit (Key<? extends PersistentRecord>.Expression key)
     {
-        _builder.append(" where ");
         Class<? extends PersistentRecord> pClass = key.getPersistentClass();
         String[] keyFields = KeyUtil.getKeyFields(pClass);
         List<Comparable<?>> values = key.getValues();

src/java/com/samskivert/jdbc/depot/Key.java

@@ -41,6 +41,24 @@ import com.samskivert.util.StringUtil;
 public class Key<T extends PersistentRecord> extends WhereClause
     implements SQLExpression, CacheKey, ValidatingCacheInvalidator, Serializable
 {
+    /** Handles the matching of the key columns to its bound values. This is needed so that we can
+     * combine a buncy of keys into a {@link KeySet}. */
+    public class Expression implements SQLExpression
+    {
+        public Class<T> getPersistentClass () {
+            return Key.this.getPersistentClass();
+        }
+        public List<Comparable<?>> getValues () {
+            return Key.this.getValues();
+        }
+        public void accept (ExpressionVisitor builder) {
+            builder.visit(this);
+        }
+        public void addClasses (Collection<Class<? extends PersistentRecord>> classSet) {
+            classSet.add(getPersistentClass());
+        }
+    }
+
     /**
      * Constructs a new single-column {@code Key} with the given value.
      */
@@ -130,7 +148,7 @@ public class Key<T extends PersistentRecord> extends WhereClause
     // from WhereClause
     public SQLExpression getWhereExpression ()
     {
-        throw new UnsupportedOperationException("Key is bound specially.");
+        return new Expression();
     }
 
     // from SQLExpression

src/java/com/samskivert/jdbc/depot/KeySet.java

@@ -72,7 +72,7 @@ public class KeySet<T extends PersistentRecord> extends WhereClause
             SQLExpression[] keyArray = new SQLExpression[keys.size()];
             int ii = 0;
             for (Key<T> key : keys) {
-                keyArray[ii++] = key;
+                keyArray[ii++] = key.getWhereExpression();
             }
             _condition = new Logic.Or(keyArray);
         }

src/java/com/samskivert/jdbc/depot/expression/ExpressionVisitor.java

@@ -69,7 +69,7 @@ public interface ExpressionVisitor
     public void visit (LiteralExp literalExp);
     public void visit (ValueExp valueExp);
     public void visit (WhereClause where);
-    public void visit (Key<? extends PersistentRecord> key);
+    public void visit (Key<? extends PersistentRecord>.Expression key);
     public void visit (MultiKey<? extends PersistentRecord> key);
     public void visit (Exists<? extends PersistentRecord> exists);
     public void visit (SelectClause<? extends PersistentRecord> selectClause);