Profiling: the jar file can now be installed as an agent using java -javaagent:h2*.jar

h2/src/main/META-INF/MANIFEST.MF

@@ -13,3 +13,4 @@ Bundle-Vendor: H2 Group
 Bundle-Version: ${version}
 DynamicImport-Package: *
 Export-Package: org.h2,org.h2.api,org.h2.fulltext,org.h2.jdbcx,org.h2.tools,org.h2.util
+Premain-Class: org.h2.util.Profiler

h2/src/test/org/h2/test/utils/MemoryFootprint.java

+/*
+ * Copyright 2004-2010 H2 Group. Multiple-Licensed under the H2 License,
+ * Version 1.0, and under the Eclipse Public License, Version 1.0
+ * (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.test.utils;
+
+import java.io.IOException;
+import java.lang.instrument.Instrumentation;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import org.h2.engine.Constants;
+import org.h2.result.Row;
+import org.h2.store.Data;
+import org.h2.util.Profiler;
+import org.h2.value.Value;
+
+/**
+ * Calculate the memory footprint of various objects.
+ */
+public class MemoryFootprint {
+
+    /**
+     * Run just this test.
+     *
+     * @param a ignored
+     */
+    public static void main(String... a) throws IOException {
+        // System.getProperties().store(System.out, "");
+        print("Object", new Object());
+        print("Timestamp", new java.sql.Timestamp(0));
+        print("Date", new java.sql.Date(0));
+        print("Time", new java.sql.Time(0));
+        print("BigDecimal", new BigDecimal("0"));
+        print("BigInteger", new BigInteger("0"));
+        print("String", new String("Hello"));
+        print("Data", Data.create(null, 10));
+        print("Row", new Row(new Value[0], 0));
+        System.out.println();
+        for (int i = 1; i < 128; i += i) {
+
+            System.out.println(getArraySize(1, i) + " bytes per p1[]");
+            print("boolean[" + i +"]", new boolean[i]);
+
+            System.out.println(getArraySize(2, i) + " bytes per p2[]");
+            print("char[" + i +"]", new char[i]);
+            print("short[" + i +"]", new short[i]);
+
+            System.out.println(getArraySize(4, i) + " bytes per p4[]");
+            print("int[" + i +"]", new int[i]);
+            print("float[" + i +"]", new float[i]);
+
+            System.out.println(getArraySize(8, i) + " bytes per p8[]");
+            print("long[" + i +"]", new long[i]);
+            print("double[" + i +"]", new double[i]);
+
+            System.out.println(getArraySize(Constants.MEMORY_POINTER, i) + " bytes per obj[]");
+            print("Object[" + i +"]", new Object[i]);
+
+            System.out.println();
+        }
+    }
+
+    private static int getArraySize(int type, int length) {
+        return ((Constants.MEMORY_OBJECT + length * type) + 7) / 8 * 8;
+    }
+
+    private static void print(String type, Object o) {
+        System.out.println(getObjectSize(o) + " bytes per " + type);
+    }
+
+    /**
+     * Get the number of bytes required for the given object.
+     * This method only works if the agent is set.
+     *
+     * @param o the object
+     * @return the number of bytes required
+     */
+    public static long getObjectSize(Object o) {
+        Instrumentation inst = Profiler.getInstrumentation();
+        return inst == null ? 0 : inst.getObjectSize(o);
+    }
+
+}