cache disk blocks in an LRU cache

Improves read access by factor 4 for small trees.

block-storage/src/test/java/org/lucares/pdb/map/PersistentMapDiskNodeTest.java

@@ -1,10 +1,12 @@
 package org.lucares.pdb.map;
 
+import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.ThreadLocalRandom;
 
+import org.lucares.pdb.diskstorage.DiskBlock;
 import org.lucares.pdb.map.NodeEntry.ValueType;
 import org.testng.Assert;
 import org.testng.annotations.Test;
@@ -21,11 +23,13 @@ public class PersistentMapDiskNodeTest {
 		entries.add(newNode(ValueType.VALUE_INLINE, "key4___", "value4----"));
 
 		final long nodeOffset = ThreadLocalRandom.current().nextInt();
-		final PersistentMapDiskNode node = new PersistentMapDiskNode(nodeOffset, entries);
+		final PersistentMapDiskNode node = new PersistentMapDiskNode(nodeOffset, entries, null);
 
 		final byte[] buffer = node.serialize();
 
-		final PersistentMapDiskNode actualNode = PersistentMapDiskNode.parse(nodeOffset, buffer);
+		final ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
+		final PersistentMapDiskNode actualNode = PersistentMapDiskNode.parse(nodeOffset,
+				new DiskBlock(nodeOffset, byteBuffer));
 
 		Assert.assertEquals(actualNode.getEntries(), entries);
 	}

block-storage/src/test/java/org/lucares/pdb/map/PersistentMapTest.java

@@ -57,6 +57,7 @@ public class PersistentMapTest {
 		}
 	}
 
+	@Test(invocationCount = 1)
 	public void testManyValues() throws Exception {
 		final Path file = dataDirectory.resolve("map.db");
 		final var insertedValues = new HashMap<String, String>();
@@ -118,7 +119,7 @@ public class PersistentMapTest {
 		}
 	}
 
-	@Test
+	@Test(invocationCount = 1)
 	public void testManySmallValues() throws Exception {
 		final Path file = dataDirectory.resolve("map.db");
 		final var insertedValues = new HashMap<Long, Long>();
@@ -267,4 +268,64 @@ public class PersistentMapTest {
 		}
 	}
 
+	@Test(invocationCount = 1)
+	public void testLotsOfValues() throws Exception {
+		final Path file = dataDirectory.resolve("map.db");
+		final var insertedValues = new HashMap<Long, Long>();
+
+		final SecureRandom rnd = new SecureRandom();
+		rnd.setSeed(1);
+
+		try (final PersistentMap<Long, Long> map = new PersistentMap<>(file, PersistentMap.LONG_CODER,
+				PersistentMap.LONG_CODER)) {
+
+			for (int i = 0; i < 1_000; i++) {
+
+				final Long key = (long) (rnd.nextGaussian() * Integer.MAX_VALUE);
+				final Long value = (long) (rnd.nextGaussian() * Integer.MAX_VALUE);
+
+				if (insertedValues.containsKey(key)) {
+					continue;
+				}
+
+				Assert.assertNull(map.putValue(key, value));
+
+				insertedValues.put(key, value);
+
+				final boolean failEarly = false;
+				if (failEarly) {
+					for (final var entry : insertedValues.entrySet()) {
+						final Long actualValue = map.getValue(entry.getKey());
+
+						if (!Objects.equals(actualValue, entry.getValue())) {
+							map.print();
+						}
+
+						Assert.assertEquals(actualValue, entry.getValue(),
+								"value for key " + entry.getKey() + " in the " + i + "th iteration");
+					}
+				}
+			}
+		}
+
+		try (final PersistentMap<Long, Long> map = new PersistentMap<>(file, PersistentMap.LONG_CODER,
+				PersistentMap.LONG_CODER)) {
+			final AtomicInteger counter = new AtomicInteger();
+			final AtomicInteger maxDepth = new AtomicInteger();
+			map.visitNodeEntriesPreOrder((node, parentNode, nodeEntry, depth) -> {
+				counter.addAndGet(nodeEntry.isInnerNode() ? 1 : 0);
+				maxDepth.set(Math.max(maxDepth.get(), depth));
+			});
+
+			final long start = System.nanoTime();
+			for (final var entry : insertedValues.entrySet()) {
+				final Long actualValue = map.getValue(entry.getKey());
+				Assert.assertEquals(actualValue, entry.getValue(),
+						"value for key " + entry.getKey() + " after all iterations");
+			}
+			System.out.println("nodes=" + counter.get() + ", depth=" + maxDepth.get() + ": "
+					+ (System.nanoTime() - start) / 1_000_000.0 + "ms");
+		}
+	}
+
 }