add an option to control size of compress later cache in the nioMemLZF filesystem

h2/src/docsrc/html/advanced.html

@@ -1589,7 +1589,10 @@ The following file systems are included:
 </li><li><code>memFS:</code> in-memory file system (slower than mem; experimental; mainly used for testing the database engine itself).
 </li><li><code>memLZF:</code> compressing in-memory file system (slower than memFS but uses less memory; experimental; mainly used for testing the database engine itself).
 </li><li><code>nioMemFS:</code> stores data outside of the VM's heap - useful for large memory DBs without incurring GC costs.
-</li><li><code>nioMemLZF:</code> stores compressed data outside of the VM's heap - useful for large memory DBs without incurring GC costs.
+</li>
+<li>
+    <code>nioMemLZF:</code> stores compressed data outside of the VM's heap - useful for large memory DBs without incurring GC costs.
+    <p>use "nioMemLZF:12:" to tweak the % of blocks that are stored uncompressed. If you size this to your working set correctly, compressed storage is roughly the same performance as uncompressed. The default value is 1%.
 </li></ul>
 <p>
 As an example, to use the the <code>nio</code> file system, use the following database URL:

h2/src/docsrc/html/changelog.html

@@ -21,6 +21,10 @@ Change Log
 
 <h2>Next Version (unreleased)</h2>
 <ul>
+<li>The "nioMemLZF" filesystem now supports an extra option "nioMemLZF:12:" to tweak the size of the compress later cache.
+</li>
+<li>Various multi-threading fixes and optimisations to the "nioMemLZF" filesystem.
+</li>
 <li><strong>[API CHANGE]</strong> #439: the JDBC type of TIMESTAMP WITH TIME ZONE
 changed from Types.OTHER (1111) to Types.TIMESTAMP_WITH_TIMEZONE (2014)
 </li>

h2/src/main/org/h2/store/fs/FilePathNioMem.java

@@ -33,6 +33,7 @@ public class FilePathNioMem extends FilePath {
 
     private static final TreeMap<String, FileNioMemData> MEMORY_FILES =
             new TreeMap<String, FileNioMemData>();
+    float compressLaterCachePercent = 1;
 
     @Override
     public FilePathNioMem getPath(String path) {
@@ -184,14 +185,14 @@ public class FilePathNioMem extends FilePath {
         synchronized (MEMORY_FILES) {
             FileNioMemData m = MEMORY_FILES.get(name);
             if (m == null) {
-                m = new FileNioMemData(name, compressed());
+                m = new FileNioMemData(name, compressed(), compressLaterCachePercent);
                 MEMORY_FILES.put(name, m);
             }
             return m;
         }
     }
 
-    private boolean isRoot() {
+    protected boolean isRoot() {
         return name.equals(getScheme() + ":");
     }
 
@@ -204,7 +205,7 @@ public class FilePathNioMem extends FilePath {
      */
     protected static String getCanonicalPath(String fileName) {
         fileName = fileName.replace('\\', '/');
-        int idx = fileName.indexOf(':') + 1;
+        int idx = fileName.lastIndexOf(':') + 1;
         if (fileName.length() > idx && fileName.charAt(idx) != '/') {
             fileName = fileName.substring(0, idx) + "/" + fileName.substring(idx);
         }
@@ -219,7 +220,7 @@ public class FilePathNioMem extends FilePath {
     /**
      * Whether the file should be compressed.
      *
-     * @return if it should be compressed.
+     * @return true if it should be compressed.
      */
     boolean compressed() {
         return false;
@@ -239,11 +240,25 @@ class FilePathNioMemLZF extends FilePathNioMem {
 
     @Override
     public FilePathNioMem getPath(String path) {
-        FilePathNioMemLZF p = new FilePathNioMemLZF();
+        if (!path.startsWith(getScheme())) {
+            throw new IllegalArgumentException(path +
+                    " doesn't start with " + getScheme());
+        }
+        int idx1 = path.indexOf(":");
+        int idx2 = path.lastIndexOf(":");
+        final FilePathNioMemLZF p = new FilePathNioMemLZF();
+        if (idx1 != -1 && idx1 != idx2) {
+            p.compressLaterCachePercent = Float.parseFloat(path.substring(idx1 + 1, idx2));
+        }
         p.name = getCanonicalPath(path);
         return p;
     }
 
+    @Override
+    protected boolean isRoot() {
+        return name.lastIndexOf(":") == name.length() - 1;
+    }
+
     @Override
     public String getScheme() {
         return "nioMemLZF";
@@ -396,7 +411,7 @@ class FileNioMem extends FileBase {
  */
 class FileNioMemData {
 
-    private static final int CACHE_SIZE = 8;
+    private static final int CACHE_MIN_SIZE = 8;
     private static final int BLOCK_SIZE_SHIFT = 16;
 
     private static final int BLOCK_SIZE = 1 << BLOCK_SIZE_SHIFT;
@@ -418,11 +433,12 @@ class FileNioMemData {
     };
 
     private final CompressLaterCache<CompressItem, CompressItem> compressLaterCache =
-        new CompressLaterCache<CompressItem, CompressItem>(CACHE_SIZE);
+        new CompressLaterCache<CompressItem, CompressItem>(CACHE_MIN_SIZE);
 
     private String name;
     private final int nameHashCode;
     private final boolean compress;
+    private final float compressLaterCachePercent;
     private long length;
     private AtomicReference<ByteBuffer>[] buffers;
     private long lastModified;
@@ -440,10 +456,11 @@ class FileNioMemData {
     }
 
     @SuppressWarnings("unchecked")
-    FileNioMemData(String name, boolean compress) {
+    FileNioMemData(String name, boolean compress, float compressLaterCachePercent) {
         this.name = name;
         this.nameHashCode = name.hashCode();
         this.compress = compress;
+        this.compressLaterCachePercent = compressLaterCachePercent;
         buffers = new AtomicReference[0];
         lastModified = System.currentTimeMillis();
     }
@@ -491,7 +508,7 @@ class FileNioMemData {
     static class CompressLaterCache<K, V> extends LinkedHashMap<K, V> {
 
         private static final long serialVersionUID = 1L;
-        private final int size;
+        private int size;
 
         CompressLaterCache(int size) {
             super(size, (float) 0.75, true);
@@ -507,6 +524,10 @@ class FileNioMemData {
             c.data.compressPage(c.page);
             return true;
         }
+
+        public void setCacheSize(int size) {
+            this.size = size;
+        }
     }
 
     /**
@@ -650,6 +671,7 @@ class FileNioMemData {
             }
             buffers = newBuffers;
         }
+        compressLaterCache.setCacheSize(Math.max(CACHE_MIN_SIZE, (int)(blocks * compressLaterCachePercent / 100)));
     }
 
     /**

h2/src/test/org/h2/test/unit/TestFileSystem.java

@@ -23,7 +23,6 @@ import java.util.List;
 import java.util.Random;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipOutputStream;
-
 import org.h2.dev.fs.FilePathZip2;
 import org.h2.message.DbException;
 import org.h2.mvstore.DataUtils;
@@ -86,6 +85,7 @@ public class TestFileSystem extends TestBase {
         testFileSystem("memLZF:");
         testFileSystem("nioMemFS:");
         testFileSystem("nioMemLZF:");
+        testFileSystem("nioMemLZF:12:"); // 12% compressLaterCache
         testFileSystem("rec:memFS:");
         testUserHome();
         try {