Merge pull request #1229 from katzyn/undolog

Create UndoLog only when necessary and remove outdated code

h2/src/main/org/h2/command/Command.java

@@ -290,7 +290,7 @@ public abstract class Command implements CommandInterface {
                     if (s.getErrorCode() == ErrorCode.DEADLOCK_1) {
                         session.rollback();
                     } else {
-                        session.rollbackTo(rollback, false);
+                        session.rollbackTo(rollback);
                     }
                 } catch (Throwable nested) {
                     e.addSuppressed(nested);

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

@@ -130,12 +130,6 @@ public class DbSettings extends SettingsBase {
      */
     public final boolean functionsInSchema = get("FUNCTIONS_IN_SCHEMA", true);
 
-    /**
-     * Database setting <code>LARGE_TRANSACTIONS</code> (default: true).<br />
-     * Support very large transactions
-     */
-    public final boolean largeTransactions = get("LARGE_TRANSACTIONS", true);
-
     /**
      * Database setting <code>LOB_TIMEOUT</code> (default: 300000,
      * which means 5 minutes).<br />

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

@@ -85,7 +85,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
     private final User user;
     private final int id;
     private final ArrayList<Table> locks = Utils.newSmallArrayList();
-    private final UndoLog undoLog;
+    private UndoLog undoLog;
     private boolean autoCommit = true;
     private Random random;
     private int lockTimeout;
@@ -168,7 +168,6 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
         this.database = database;
         this.queryTimeout = database.getSettings().maxQueryTimeout;
         this.queryCacheSize = database.getSettings().queryCacheSize;
-        this.undoLog = new UndoLog(this);
         this.user = user;
         this.id = id;
         this.lockTimeout = database.getLockTimeout();
@@ -691,7 +690,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
             database.commit(this);
         }
         removeTemporaryLobs(true);
-        if (undoLog.size() > 0) {
+        if (undoLog != null && undoLog.size() > 0) {
             undoLog.clear();
         }
         if (!ddl) {
@@ -761,9 +760,9 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
         checkCommitRollback();
         currentTransactionName = null;
         transactionStart = null;
-        boolean needCommit = undoLog.size() > 0 || transaction != null;
-        if(needCommit) {
-            rollbackTo(null, false);
+        boolean needCommit = undoLog != null && undoLog.size() > 0 || transaction != null;
+        if (needCommit) {
+            rollbackTo(null);
         }
         if (!locks.isEmpty() || needCommit) {
             database.commit(this);
@@ -780,14 +779,15 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
      * Partially roll back the current transaction.
      *
      * @param savepoint the savepoint to which should be rolled back
-     * @param trimToSize if the list should be trimmed
      */
-    public void rollbackTo(Savepoint savepoint, boolean trimToSize) {
+    public void rollbackTo(Savepoint savepoint) {
         int index = savepoint == null ? 0 : savepoint.logIndex;
+        if (undoLog != null) {
             while (undoLog.size() > index) {
                 UndoLogRecord entry = undoLog.getLast();
                 entry.undo(this);
-            undoLog.removeLast(trimToSize);
+                undoLog.removeLast();
+            }
         }
         if (transaction != null) {
             if (savepoint == null) {
@@ -818,7 +818,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
 
     @Override
     public boolean hasPendingTransaction() {
-        return undoLog.size() > 0;
+        return undoLog != null && undoLog.size() > 0;
     }
 
     /**
@@ -828,7 +828,9 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
      */
     public Savepoint setSavepoint() {
         Savepoint sp = new Savepoint();
+        if (undoLog != null) {
             sp.logIndex = undoLog.size();
+        }
         if (database.getMvStore() != null) {
             sp.transactionSavepoint = getStatementSavepoint();
         }
@@ -856,7 +858,9 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
 
                 removeTemporaryLobs(false);
                 cleanTempTables(true);
+                if (undoLog != null) {
                     undoLog.clear();
+                }
                 // Table#removeChildrenAndResources can take the meta lock,
                 // and we need to unlock before we call removeSession(), which might
                 // want to take the meta lock using the system session.
@@ -910,6 +914,9 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
                     }
                 }
             }
+            if (undoLog == null) {
+                undoLog = new UndoLog(database);
+            }
             undoLog.add(log);
         }
     }
@@ -942,7 +949,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
 
     private void unlockAll() {
         if (SysProperties.CHECK) {
-            if (undoLog.size() > 0) {
+            if (undoLog != null && undoLog.size() > 0) {
                 DbException.throwInternalError();
             }
         }
@@ -1085,12 +1092,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
         if (savepoints == null) {
             savepoints = database.newStringMap();
         }
-        Savepoint sp = new Savepoint();
-        sp.logIndex = undoLog.size();
-        if (database.getMvStore() != null) {
-            sp.transactionSavepoint = getStatementSavepoint();
-        }
-        savepoints.put(name, sp);
+        savepoints.put(name, setSavepoint());
     }
 
     /**
@@ -1109,7 +1111,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
         if (savepoint == null) {
             throw DbException.get(ErrorCode.SAVEPOINT_IS_INVALID_1, name);
         }
-        rollbackTo(savepoint, false);
+        rollbackTo(savepoint);
     }
 
     /**
@@ -1619,7 +1621,7 @@ public class Session extends SessionWithState implements TransactionStore.Rollba
         if (!database.isPersistent()) {
             return ValueNull.INSTANCE;
         }
-        if (undoLog.size() == 0) {
+        if (undoLog == null || undoLog.size() == 0) {
             return ValueNull.INSTANCE;
         }
         return ValueString.get(firstUncommittedLog + "-" + firstUncommittedPos +

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

@@ -8,7 +8,6 @@ package org.h2.engine;
 import java.util.ArrayList;
 import java.util.HashMap;
 
-import org.h2.message.DbException;
 import org.h2.store.Data;
 import org.h2.store.FileStore;
 import org.h2.table.Table;
@@ -27,16 +26,14 @@ public class UndoLog {
     private int memoryUndo;
     private int storedEntries;
     private HashMap<Integer, Table> tables;
-    private final boolean largeTransactions;
 
     /**
      * Create a new undo log for the given session.
      *
-     * @param session the session
+     * @param database the database
      */
-    UndoLog(Session session) {
-        this.database = session.getDatabase();
-        largeTransactions = database.getSettings().largeTransactions;
+    UndoLog(Database database) {
+        this.database = database;
     }
 
     /**
@@ -45,14 +42,8 @@ public class UndoLog {
      * @return the number of rows
      */
     int size() {
-        if (largeTransactions) {
         return storedEntries + records.size();
     }
-        if (SysProperties.CHECK && memoryUndo > records.size()) {
-            DbException.throwInternalError();
-        }
-        return records.size();
-    }
 
     /**
      * Clear the undo log. This method is called after the transaction is
@@ -77,7 +68,6 @@ public class UndoLog {
      */
     public UndoLogRecord getLast() {
         int i = records.size() - 1;
-        if (largeTransactions) {
         if (i < 0 && storedEntries > 0) {
             int last = storedEntriesPos.size() - 1;
             long pos = storedEntriesPos.remove(last);
@@ -96,7 +86,6 @@ public class UndoLog {
             file.seek(pos);
         }
         i = records.size() - 1;
-        }
         UndoLogRecord entry = records.get(i);
         if (entry.isStored()) {
             int start = Math.max(0, i - database.getMaxMemoryUndo() / 2);
@@ -131,18 +120,13 @@ public class UndoLog {
 
     /**
      * Remove the last record from the list of operations.
-     *
-     * @param trimToSize if the undo array should shrink to conserve memory
      */
-    void removeLast(boolean trimToSize) {
+    void removeLast() {
         int i = records.size() - 1;
         UndoLogRecord r = records.remove(i);
         if (!r.isStored()) {
             memoryUndo--;
         }
-        if (trimToSize && i > 1024 && (i & 1023) == 0) {
-            records.trimToSize();
-        }
     }
 
     /**
@@ -152,7 +136,6 @@ public class UndoLog {
      */
     void add(UndoLogRecord entry) {
         records.add(entry);
-        if (largeTransactions) {
         memoryUndo++;
         if (memoryUndo > database.getMaxMemoryUndo() &&
                 database.isPersistent() &&
@@ -179,36 +162,6 @@ public class UndoLog {
             records.clear();
             file.autoDelete();
         }
-        } else {
-            if (!entry.isStored()) {
-                memoryUndo++;
-            }
-            if (memoryUndo > database.getMaxMemoryUndo() &&
-                    database.isPersistent() &&
-                    !database.isMVStore()) {
-                if (file == null) {
-                    String fileName = database.createTempFile();
-                    file = database.openFile(fileName, "rw", false);
-                    file.setCheckedWriting(false);
-                    file.seek(FileStore.HEADER_LENGTH);
-                    rowBuff = Data.create(database, Constants.DEFAULT_PAGE_SIZE);
-                    Data buff = rowBuff;
-                    for (UndoLogRecord r : records) {
-                        saveIfPossible(r, buff);
-                    }
-                } else {
-                    saveIfPossible(entry, rowBuff);
-                }
-                file.autoDelete();
-            }
-        }
-    }
-
-    private void saveIfPossible(UndoLogRecord r, Data buff) {
-        if (!r.isStored() && r.canStore()) {
-            r.save(buff, file, this);
-            memoryUndo--;
-        }
     }
 
     /**

h2/src/main/org/h2/table/Table.java

@@ -515,7 +515,7 @@ public abstract class Table extends SchemaObjectBase {
             } catch (DbException e) {
                 if (e.getErrorCode() == ErrorCode.CONCURRENT_UPDATE_1
                         || e.getErrorCode() == ErrorCode.ROW_NOT_FOUND_WHEN_DELETING_1) {
-                    session.rollbackTo(rollback, false);
+                    session.rollbackTo(rollback);
                     session.startStatementWithinTransaction();
                     rollback = session.setSavepoint();
                 }
@@ -534,7 +534,7 @@ public abstract class Table extends SchemaObjectBase {
                 addRow(session, n);
             } catch (DbException e) {
                 if (e.getErrorCode() == ErrorCode.CONCURRENT_UPDATE_1) {
-                    session.rollbackTo(rollback, false);
+                    session.rollbackTo(rollback);
                     session.startStatementWithinTransaction();
                     rollback = session.setSavepoint();
                 }

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

-/*
- * Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
- * and the EPL 1.0 (http://h2database.com/html/license.html).
- * Initial Developer: H2 Group
- */
-package org.h2.test.todo;
-
-import java.sql.Connection;
-import java.sql.DriverManager;
-import java.sql.PreparedStatement;
-import java.sql.SQLException;
-import java.sql.Statement;
-import org.h2.tools.DeleteDbFiles;
-
-/**
- * A test to reproduce out of memory using a large operation.
- */
-public class TestUndoLogMemory {
-
-    /**
-     * Run just this test.
-     *
-     * @param args ignored
-     */
-    public static void main(String... args) throws Exception {
-        TestUndoLogMemory.test(10, "null");
-        TestUndoLogMemory.test(100, "space(100000)");
-        // new TestUndoLogMemory().test(100000, "null");
-        // new TestUndoLogMemory().test(1000, "space(100000)");
-    }
-
-    private static void test(int count, String defaultValue) throws SQLException {
-
-        // -Xmx1m -XX:+HeapDumpOnOutOfMemoryError
-        DeleteDbFiles.execute("data", "test", true);
-        Connection conn = DriverManager.getConnection(
-                "jdbc:h2:data/test;large_transactions=true");
-        Statement stat = conn.createStatement();
-        stat.execute("set cache_size 32");
-        stat.execute("SET max_operation_memory 100");
-        stat.execute("SET max_memory_undo 100");
-        conn.setAutoCommit(false);
-
-        // also a problem: tables without unique index
-        System.out.println("create--- " + count + " " + defaultValue);
-        stat.execute("create table test(id int, name varchar default " +
-                defaultValue + " )");
-        System.out.println("insert---");
-        stat.execute("insert into test(id) select x from system_range(1, " +
-                count + ")");
-        System.out.println("rollback---");
-        conn.rollback();
-
-        System.out.println("drop---");
-        stat.execute("drop table test");
-        System.out.println("create---");
-        stat.execute("create table test" +
-                "(id int primary key, name varchar default " +
-                defaultValue + " )");
-
-        // INSERT problem
-        System.out.println("insert---");
-        stat.execute(
-            "insert into test(id) select x from system_range(1, "+count+")");
-        System.out.println("delete---");
-        stat.execute("delete from test");
-
-        // DELETE problem
-        System.out.println("insert---");
-        PreparedStatement prep = conn.prepareStatement(
-                "insert into test(id) values(?)");
-        for (int i = 0; i < count; i++) {
-            prep.setInt(1, i);
-            prep.execute();
-        }
-        System.out.println("delete---");
-        stat.execute("delete from test");
-
-        System.out.println("close---");
-        conn.close();
-    }
-
-}