Storing lobs in the database has been changed. It is now faster.

h2/src/main/org/h2/store/LobStorage.java

@@ -51,11 +51,13 @@ public class LobStorage {
 
     private static final int BLOCK_LENGTH = 20000;
     private static final boolean HASH = true;
-    private static final long UNIQUE = 0xffff;
+    // each entry needs 16 bytes (2 longs)
+    private static final int HASH_CACHE_SIZE = 8 * 1024;
     private Connection conn;
     private HashMap<String, PreparedStatement> prepared = New.hashMap();
     private long nextBlock;
     private CompressTool compress = CompressTool.getInstance();
+    private long[] hashBlocks = new long[HASH_CACHE_SIZE * 2];
 
     private final DataHandler handler;
     private boolean init;
@@ -83,14 +85,11 @@ public class LobStorage {
             stat.execute("CREATE TABLE IF NOT EXISTS " + LOBS + "(ID BIGINT PRIMARY KEY, BYTE_COUNT BIGINT, TABLE INT) HIDDEN");
             stat.execute("CREATE TABLE IF NOT EXISTS " + LOB_MAP + "(LOB BIGINT, SEQ INT, BLOCK BIGINT, PRIMARY KEY(LOB, SEQ)) HIDDEN");
             stat.execute("CREATE INDEX IF NOT EXISTS INFORMATION_SCHEMA.INDEX_LOB_MAP_DATA_LOB ON " + LOB_MAP + "(BLOCK, LOB)");
-            stat.execute("CREATE TABLE IF NOT EXISTS " + LOB_DATA + "(BLOCK BIGINT PRIMARY KEY, COMPRESSED INT, DATA BINARY) HIDDEN");
+            stat.execute("CREATE TABLE IF NOT EXISTS " + LOB_DATA + "(BLOCK BIGINT PRIMARY KEY, COMPRESSED INT, HASH INT, DATA BINARY) HIDDEN");
             ResultSet rs;
             rs = stat.executeQuery("SELECT MAX(BLOCK) FROM " + LOB_DATA);
             rs.next();
             nextBlock = rs.getLong(1) + 1;
-            if (HASH) {
-                nextBlock = Math.max(UNIQUE + 1, nextBlock);
-            }
         } catch (SQLException e) {
             throw DbException.convert(e);
         }
@@ -405,31 +404,44 @@ public class LobStorage {
         if (compressAlgorithm != null) {
             b = compress.compress(b, compressAlgorithm);
         }
+        int hash = Arrays.hashCode(b);
         if (HASH) {
-            block = Arrays.hashCode(b) & UNIQUE;
+            block = 0;
+            int index = hash & (HASH_CACHE_SIZE - 1);
+            long oldHash = hashBlocks[index];
+int hashTableAddWhenReading;
+int hashTableRemoveWhenDeleting;
+            if (oldHash == hash) {
+                long old = hashBlocks[index + HASH_CACHE_SIZE];
                 PreparedStatement prep = prepare(
                         "SELECT COMPRESSED, DATA FROM " + LOB_DATA +
                         " WHERE BLOCK = ?");
-            prep.setLong(1, block);
+                prep.setLong(1, old);
                 ResultSet rs = prep.executeQuery();
                 if (rs.next()) {
                     boolean compressed = rs.getInt(1) != 0;
                     byte[] compare = rs.getBytes(2);
                     if (Arrays.equals(b, compare) && compressed == (compressAlgorithm != null)) {
                         blockExists = true;
-                } else {
-                    block = nextBlock++;
+                        block = old;
                     }
                 }
+            }
+            if (!blockExists) {
+                block = nextBlock++;
+            }
+            hashBlocks[index] = hash;
+            hashBlocks[index + HASH_CACHE_SIZE] = block;
         } else {
             block = nextBlock++;
         }
         if (!blockExists) {
             PreparedStatement prep = prepare(
-                    "INSERT INTO " + LOB_DATA + "(BLOCK, COMPRESSED, DATA) VALUES(?, ?, ?)");
+                    "INSERT INTO " + LOB_DATA + "(BLOCK, COMPRESSED, HASH, DATA) VALUES(?, ?, ?, ?)");
             prep.setLong(1, block);
             prep.setInt(2, compressAlgorithm == null ? 0 : 1);
-            prep.setBytes(3, b);
+            prep.setInt(3, hash);
+            prep.setBytes(4, b);
             prep.execute();
         }
         PreparedStatement prep = prepare(

h2/src/test/org/h2/test/db/TestLob.java

@@ -44,6 +44,7 @@ public class TestLob extends TestBase {
      * @param a ignored
      */
     public static void main(String... a) throws Exception {
+        System.setProperty("h2.lobInDatabase", "true");
         TestBase.createCaller().init().test();
     }