Flush on byte size

src/main/java/com/tomfran/lsm/memtable/Memtable.java

@@ -8,21 +8,14 @@
 public class Memtable implements Iterable<ByteArrayPair> {
 
     SkipList list;
+    long byteSize;
 
     /**
      * Initialize a Memtable with default list size.
      */
     public Memtable() {
         list = new SkipList();
-    }
-
-    /**
-     * Initialize a Memtable with an expected number of elements.
-     *
-     * @param numElements the expected max size of the underlying list.
-     */
-    public Memtable(int numElements) {
-        list = new SkipList(numElements);
+        byteSize = 0L;
     }
 
     /**
@@ -32,6 +25,7 @@ public Memtable(int numElements) {
      */
     public void add(ByteArrayPair item) {
         list.add(item);
+        byteSize += item.size();
     }
 
     /**
@@ -54,12 +48,12 @@ public void remove(byte[] key) {
     }
 
     /**
-     * Get size of the underlying list.
+     * Return the size in bytes of the skiplist.
      *
-     * @return the list size.
+     * @return bytes indicating size of underlying list.
      */
-    public int size() {
-        return list.size();
+    public long byteSize() {
+        return byteSize;
     }
 
     /**

src/main/java/com/tomfran/lsm/memtable/SkipList.java

@@ -14,7 +14,7 @@
  */
 public class SkipList implements Iterable<ByteArrayPair> {
 
-    static final int DEFAULT_ELEMENTS = 1 << 16;
+    static final int DEFAULT_ELEMENTS = 1 << 20;
 
     final Node sentinel;
 

src/main/java/com/tomfran/lsm/tree/LSMTree.java

@@ -25,7 +25,7 @@
  */
 public class LSMTree {
 
-    static final int DEFAULT_MEMTABLE_MAX_SIZE = 1 << 10;
+    static final long DEFAULT_MEMTABLE_MAX__BYTE_SIZE = 1024 * 1024 * 256;
     static final int DEFAULT_TABLE_LEVEL_MAX_SIZE = 5;
     static final int DEFAULT_SSTABLE_SAMPLE_SIZE = 1 << 10;
     static final String DEFAULT_DATA_DIRECTORY = "LSM-data";
@@ -34,7 +34,7 @@ public class LSMTree {
     final Object immutableMemtablesLock = new Object();
     final Object tableLock = new Object();
 
-    final int mutableMemtableMaxSize;
+    final long mutableMemtableMaxSize;
     final int tableLevelMaxSize;
     final String dataDir;
 
@@ -48,22 +48,22 @@ public class LSMTree {
      * Creates a new LSMTree with a default memtable size and data directory.
      */
     public LSMTree() {
-        this(DEFAULT_MEMTABLE_MAX_SIZE, DEFAULT_TABLE_LEVEL_MAX_SIZE, DEFAULT_DATA_DIRECTORY);
+        this(DEFAULT_MEMTABLE_MAX__BYTE_SIZE, DEFAULT_TABLE_LEVEL_MAX_SIZE, DEFAULT_DATA_DIRECTORY);
     }
 
     /**
      * Creates a new LSMTree with a memtable size and data directory.
      *
-     * @param mutableMemtableMaxSize The maximum size of the memtable before it is flushed to disk.
+     * @param mutableMemtableMaxByteSize The maximum size of the memtable before it is flushed to disk.
      * @param dataDir                The directory to store the data in.
      */
-    public LSMTree(int mutableMemtableMaxSize, int tableLevelMaxSize, String dataDir) {
-        this.mutableMemtableMaxSize = mutableMemtableMaxSize;
+    public LSMTree(long mutableMemtableMaxByteSize, int tableLevelMaxSize, String dataDir) {
+        this.mutableMemtableMaxSize = mutableMemtableMaxByteSize;
         this.tableLevelMaxSize = tableLevelMaxSize;
         this.dataDir = dataDir;
         createDataDir();
 
-        mutableMemtable = new Memtable(mutableMemtableMaxSize);
+        mutableMemtable = new Memtable();
         immutableMemtables = new LinkedList<>();
         tables = new ObjectArrayList<>();
         tables.add(new LinkedList<>());
@@ -132,18 +132,18 @@ public byte[] get(byte[] key) {
     /**
      * Stop the background threads.
      */
-    public void stop() throws InterruptedException {
+    public void stop() {
         memtableFlusher.shutdownNow();
         tableCompactor.shutdownNow();
     }
 
     private void checkMemtableSize() {
-        if (mutableMemtable.size() <= mutableMemtableMaxSize)
+        if (mutableMemtable.byteSize() <= mutableMemtableMaxSize)
             return;
 
         synchronized (immutableMemtablesLock) {
             immutableMemtables.addFirst(mutableMemtable);
-            mutableMemtable = new Memtable(mutableMemtableMaxSize);
+            mutableMemtable = new Memtable();
             memtableFlusher.execute(this::flushLastMemtable);
         }
     }

src/main/java/com/tomfran/lsm/types/ByteArrayPair.java

@@ -6,6 +6,10 @@
 
 public record ByteArrayPair(byte[] key, byte[] value) implements Comparable<ByteArrayPair> {
 
+    public int size() {
+        return key.length + value.length;
+    }
+
     @Override
     public int hashCode() {
         return Arrays.hashCode(key);

src/test/java/com/tomfran/lsm/TestUtils.java

@@ -20,6 +20,13 @@ public static ByteArrayPair getRandomPair() {
         );
     }
 
+    public static ByteArrayPair getRandomPair(int keyLen, int valueLen) {
+        return new ByteArrayPair(
+                getRandomByteArray(keyLen),
+                getRandomByteArray(valueLen)
+        );
+    }
+
     public static byte[] getRandomByteArray(int length) {
         byte[] bytes = new byte[length];
         rn.nextBytes(bytes);

src/test/java/com/tomfran/lsm/tree/LSMTreeTest.java

@@ -20,11 +20,11 @@ class LSMTreeTest {
     public void writeFlush() throws InterruptedException {
         LSMTree tree = new LSMTree(maxSize, levelSize, tempDirectory + "/test1");
 
-        IntStream.range(0, maxSize + 2).forEach(i -> tree.add(getRandomPair()));
+        IntStream.range(0, 10).forEach(i -> tree.add(getRandomPair(2, 2)));
 
         Thread.sleep(500);
 
-        assert tree.mutableMemtable.size() >= 1 : "mutable memtable size is " + tree.mutableMemtable.size();
+        assert tree.mutableMemtable.byteSize() >= 1 : "mutable memtable size is " + tree.mutableMemtable.byteSize();
         assert !tree.tables.get(0).isEmpty() : "table is null";
 
         tree.stop();
@@ -36,8 +36,8 @@ public void writeFlow() throws InterruptedException {
 
         Object2ObjectArrayMap<byte[], byte[]> items = new Object2ObjectArrayMap<>();
 
-        IntStream.range(0, 10 * maxSize).forEach(i -> {
-            var it = getRandomPair();
+        IntStream.range(0, 10).forEach(i -> {
+            var it = getRandomPair(2, 2);
             tree.add(it);
             items.put(it.key(), it.value());
         });