PageLog

java.lang.Object
- org.h2.pagestore.PageLog

```
public class PageLog
extends java.lang.Object
```
Transaction log mechanism. The stream contains a list of records. The data format for a record is:
- type (0: no-op, 1: undo, 2: commit, ...)
- data
The transaction log is split into sections. A checkpoint starts a new section.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`ADD` Add a record to a table.
`static int`	`CHECKPOINT` Perform a checkpoint.
`static int`	`COMMIT` A commit entry of a session.
`static int`	`FREE_LOG` Free a log page.
`static int`	`NOOP` No operation.
`static int`	`PREPARE_COMMIT` A prepare commit entry for a session.
`static int`	`REMOVE` Remove a record from a table.
`static int`	`ROLLBACK` Roll back a prepared transaction.
`static int`	`TRUNCATE` Truncate a table.
`static int`	`UNDO` An undo log entry.

Method Summary

Methods
Modifier and Type Method and Description

static Row readRow(RowFactory rowFactory, DataReader in, Data data)
Read a row from an input stream.
- Methods inherited from class java.lang.Object
  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods
Modifier and Type	Method and Description
`static Row`	`readRow(RowFactory rowFactory, DataReader in, Data data)` Read a row from an input stream.

- Field Detail
  - NOOP
```
public static final int NOOP
```
    No operation.
    
    See Also:
    Constant Field Values
  - UNDO
```
public static final int UNDO
```
    An undo log entry. Format: page id: varInt, size, page. Size 0 means uncompressed, size 1 means empty page, otherwise the size is the number of compressed bytes.
    
    See Also:
    Constant Field Values
  - COMMIT
```
public static final int COMMIT
```
    A commit entry of a session. Format: session id: varInt.
    
    See Also:
    Constant Field Values
  - PREPARE_COMMIT
```
public static final int PREPARE_COMMIT
```
    A prepare commit entry for a session. Format: session id: varInt, transaction name: string.
    
    See Also:
    Constant Field Values
  - ROLLBACK
```
public static final int ROLLBACK
```
    Roll back a prepared transaction. Format: session id: varInt.
    
    See Also:
    Constant Field Values
  - ADD
```
public static final int ADD
```
    Add a record to a table. Format: session id: varInt, table id: varInt, row.
    
    See Also:
    Constant Field Values
  - REMOVE
```
public static final int REMOVE
```
    Remove a record from a table. Format: session id: varInt, table id: varInt, row.
    
    See Also:
    Constant Field Values
  - TRUNCATE
```
public static final int TRUNCATE
```
    Truncate a table. Format: session id: varInt, table id: varInt.
    
    See Also:
    Constant Field Values
  - CHECKPOINT
```
public static final int CHECKPOINT
```
    Perform a checkpoint. The log section id is incremented. Format: -
    
    See Also:
    Constant Field Values
  - FREE_LOG
```
public static final int FREE_LOG
```
    Free a log page. Format: count: varInt, page ids: varInt
    
    See Also:
    Constant Field Values
- Method Detail
  - readRow
```
public static Row readRow(RowFactory rowFactory,
          DataReader in,
          Data data)
                   throws java.io.IOException
```
    Read a row from an input stream.
    
    Parameters:
    rowFactory - the row factory
    in - the input stream
    data - a temporary buffer
    
    Returns:
    the row
    
    Throws:
    
    java.io.IOException

Class PageLog

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NOOP

UNDO

COMMIT

PREPARE_COMMIT

ROLLBACK

ADD

REMOVE

TRUNCATE

CHECKPOINT

FREE_LOG

Method Detail

readRow