Experimental feature to support very large transactions.

h2/src/main/org/h2/engine/UndoLog.java

@@ -7,10 +7,12 @@
 package org.h2.engine;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import org.h2.constant.SysProperties;
 import org.h2.message.DbException;
 import org.h2.store.Data;
 import org.h2.store.FileStore;
+import org.h2.table.Table;
 import org.h2.util.New;
 
 /**
@@ -24,6 +26,7 @@ public class UndoLog {
     private Data rowBuff;
     private int memoryUndo;
     private int storedEntries;
+    private HashMap<Integer, Table> tables;
 
     /**
      * Create a new undo log for the given session.
@@ -73,16 +76,22 @@ public class UndoLog {
     public UndoLogRecord getLast() {
         int i = records.size() - 1;
         if (SysProperties.LARGE_TRANSACTIONS) {
+            int test;
             if (i <= 0 && storedEntries > 0) {
                 int last = storedEntriesPos.size() - 1;
                 long pos = storedEntriesPos.get(last);
                 storedEntriesPos.remove(last);
                 long end = file.length();
-                while (pos < end) {
-                    int test;
-//                    UndoLogRecord e = new UndoLogRecord(null, 0, null);
-
+                int bufferLength = (int) (end - pos);
+                Data buff = Data.create(database, bufferLength);
+                seek(pos);
+                file.readFully(buff.getBytes(), 0, bufferLength);
+                while (buff.length() < bufferLength) {
+                    UndoLogRecord e = UndoLogRecord.loadFromBuffer(buff, this);
+                    records.add(e);
+                    memoryUndo++;
                 }
+                file.setLength(pos);
             }
         }
         UndoLogRecord entry = records.get(i);
@@ -144,6 +153,26 @@ public class UndoLog {
             memoryUndo++;
         }
         if (memoryUndo > database.getMaxMemoryUndo() && database.isPersistent() && !database.isMultiVersion()) {
+            if (SysProperties.LARGE_TRANSACTIONS) {
+                int todo;
+                if (file == null) {
+                    String fileName = database.createTempFile();
+                    file = database.openFile(fileName, "rw", false);
+                    file.setLength(FileStore.HEADER_LENGTH);
+                }
+                Data buff = Data.create(database, SysProperties.PAGE_SIZE);
+                for (int i = 0; i < records.size(); i++) {
+                    UndoLogRecord r = records.get(i);
+                    buff.checkCapacity(SysProperties.PAGE_SIZE);
+                    r.append(buff, this);
+                }
+                storedEntriesPos.add(file.getFilePointer());
+                file.write(buff.getBytes(), 0, buff.length());
+                memoryUndo = 0;
+                records.clear();
+                file.autoDelete();
+                return;
+            }
             if (file == null) {
                 String fileName = database.createTempFile();
                 file = database.openFile(fileName, "rw", false);
@@ -163,9 +192,24 @@ public class UndoLog {
 
     private void saveIfPossible(UndoLogRecord r, Data buff) {
         if (!r.isStored() && r.canStore()) {
-            r.save(buff, file);
+            r.save(buff, file, this);
             memoryUndo--;
         }
     }
 
+    int getTableId(Table table) {
+        int id = table.getId();
+        if (tables == null) {
+            tables = New.hashMap();
+        }
+        if (tables.get(id) == null) {
+            tables.put(id, table);
+        }
+        return id;
+    }
+    
+    Table getTable(int id) {
+        return tables.get(id);
+    }
+
 }

h2/src/main/org/h2/engine/UndoLogRecord.java

@@ -13,7 +13,6 @@ import org.h2.message.DbException;
 import org.h2.result.Row;
 import org.h2.store.Data;
 import org.h2.store.FileStore;
-import org.h2.table.RegularTable;
 import org.h2.table.Table;
 import org.h2.value.Value;
 
@@ -69,13 +68,12 @@ public class UndoLogRecord {
      * @return if it can be stored
      */
     boolean canStore() {
-        if (table.getUniqueIndex() != null) {
-            return true;
-        }
         if (SysProperties.LARGE_TRANSACTIONS) {
-            if (table instanceof RegularTable) {
+            // actually the method is not called in this case
             return true;
         }
+        if (table.getUniqueIndex() != null) {
+            return true;
         }
         return false;
     }
@@ -136,18 +134,18 @@ public class UndoLogRecord {
     }
 
     /**
-     * Save the row in the file using a buffer.
+     * Append the row to the buffer.
      *
      * @param buff the buffer
-     * @param file the file
+     * @param log the undo log
      */
-    void save(Data buff, FileStore file) {
-        buff.reset();
+    void append(Data buff, UndoLog log) {
+        int p = buff.length();
         buff.writeInt(0);
         buff.writeInt(operation);
         buff.writeByte(row.isDeleted() ? (byte) 1 : (byte) 0);
         if (SysProperties.LARGE_TRANSACTIONS) {
-            int table;
+            buff.writeInt(log.getTableId(table));
         }
         buff.writeLong(row.getKey());
         buff.writeInt(row.getSessionId());
@@ -158,13 +156,34 @@ public class UndoLogRecord {
             buff.writeValue(v);
         }
         buff.fillAligned();
-        buff.setInt(0, buff.length() / Constants.FILE_BLOCK_SIZE);
+        buff.setInt(p, buff.length() / Constants.FILE_BLOCK_SIZE);
+    }
+    
+    /**
+     * Save the row in the file using a buffer.
+     *
+     * @param buff the buffer
+     * @param file the file
+     * @param log the undo log
+     */
+    void save(Data buff, FileStore file, UndoLog log) {
+        buff.reset();
+        append(buff, log);
         filePos = (int) (file.getFilePointer() / Constants.FILE_BLOCK_SIZE);
         file.write(buff.getBytes(), 0, buff.length());
         row = null;
         state = STORED;
     }
     
+    static UndoLogRecord loadFromBuffer(Data buff, UndoLog log) {
+        UndoLogRecord rec = new UndoLogRecord(null, (short) 0, null);
+        int pos = buff.length();
+        int len = buff.readInt() * Constants.FILE_BLOCK_SIZE;
+        rec.load(buff, log);
+        buff.setPos(pos + len);
+        return rec;
+    }
+
     /**
      * Load an undo log record row using a buffer.
      *
@@ -182,6 +201,10 @@ public class UndoLogRecord {
         if (len - min > 0) {
             file.readFully(buff.getBytes(), min, len - min);
         }
+        load(buff, log);
+    }
+    
+    private void load(Data buff, UndoLog log) {
         int op = buff.readInt();
         if (SysProperties.CHECK) {
             if (operation != op) {
@@ -190,7 +213,7 @@ public class UndoLogRecord {
         }
         boolean deleted = buff.readByte() == 1;
         if (SysProperties.LARGE_TRANSACTIONS) {
-            int table;
+            table = log.getTable(buff.readInt());
         }
         long key = buff.readLong();
         int sessionId = buff.readInt();

h2/src/test/org/h2/test/todo/TestUndoLogMemory.java

@@ -21,6 +21,8 @@ public class TestUndoLogMemory {
      * @param args ignored
      */
     public static void main(String... args) throws Exception {
+        System.setProperty("h2.largeTransactions", "true");
+        
         // -Xmx1m -XX:+HeapDumpOnOutOfMemoryError
         DeleteDbFiles.execute("data", "test", true);
         Connection conn = DriverManager.getConnection("jdbc:h2:data/test");
@@ -33,20 +35,21 @@ public class TestUndoLogMemory {
         stat.execute("create table test(id int)");
         stat.execute("insert into test select x from system_range(1, 100000)");
 
-        // stat.execute("create table test(id int primary key)");
+        stat.execute("drop table test");
+        stat.execute("create table test(id int primary key)");
 
         // INSERT problem
-        // stat.execute(
-        //     "insert into test select x from system_range(1, 400000)");
+        stat.execute(
+            "insert into test select x from system_range(1, 400000)");
+        stat.execute("delete from test");
 
         // DELETE problem
-        // stat.execute(
-        //    "insert into test select x from system_range(1, 50000)");
-        // stat.execute(
-        //     "insert into test select x from system_range(50001, 100000)");
-        // stat.execute(
-        //     "insert into test select x from system_range(100001, 150000)");
-
+        stat.execute(
+            "insert into test select x from system_range(1, 50000)");
+        stat.execute(
+             "insert into test select x from system_range(50001, 100000)");
+        stat.execute(
+            "insert into test select x from system_range(100001, 150000)");
         stat.execute("delete from test");
 
         conn.close();