diff -r 2c3cc4b01880 -r c16ac7a2eba4 src/jdk.jfr/share/classes/jdk/jfr/internal/consumer/ConstantLookup.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.jfr/share/classes/jdk/jfr/internal/consumer/ConstantLookup.java	Wed Oct 30 19:43:52 2019 +0100
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.jfr.internal.consumer;
+
+import jdk.jfr.internal.Type;
+
+final class ConstantLookup {
+    private final Type type;
+    private ConstantMap current;
+    private ConstantMap previous = ConstantMap.EMPTY;
+
+    ConstantLookup(ConstantMap current, Type type) {
+        this.current = current;
+        this.type = type;
+    }
+
+    public Type getType() {
+        return type;
+    }
+
+    public ConstantMap getLatestPool() {
+        return current;
+    }
+
+    public void newPool() {
+        previous = current;
+        current = new ConstantMap(current.factory, current.name);
+    }
+
+    public Object getPreviousResolved(long key) {
+        return previous.getResolved(key);
+    }
+
+    public Object getCurrentResolved(long key) {
+        return current.getResolved(key);
+    }
+
+    public Object getCurrent(long key) {
+        return current.get(key);
+    }
+}