FlushedScan (Apache Derby V10.14 Internals)

java.lang.Object
- org.apache.derby.impl.store.raw.log.FlushedScan

All Implemented Interfaces:: LogScan, StreamLogScan

public class FlushedScan
extends java.lang.Object
implements StreamLogScan

Scan the the log which is implemented by a series of log files.n This log scan knows how to move across log file if it is positioned at the boundary of a log file and needs to getNextRecord.

        4 bytes - length of user data, i.e. N
        8 bytes - long representing log instant
        N bytes of supplied data
        4 bytes - length of user data, i.e. N

Field Summary

Fields
Modifier and Type	Field	Description
`(package private) long`	`currentInstant`
`(package private) long`	`currentLogFileFirstUnflushedPosition`
`(package private) long`	`currentLogFileNumber`
`(package private) long`	`firstUnflushed`
`(package private) long`	`firstUnflushedFileNumber`
`(package private) long`	`firstUnflushedFilePosition`
`(package private) static int`	`LOG_REC_LEN_BYTE_LENGTH`
`(package private) LogToFile`	`logFactory`
`(package private) int`	`nextRecordLength`	The length of the next record.
`(package private) boolean`	`open`
`(package private) boolean`	`readNextRecordLength`	Flag to indicate that the length of the next log record has been read by currentLogFileHasUnflushedRecord.
`private StorageRandomAccessFile`	`scan`

Constructor Summary

Constructors
Constructor Description

FlushedScan(LogToFile logFactory, long startAt)

Constructors
Constructor	Description
`FlushedScan(LogToFile logFactory, long startAt)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`close()`	Close the scan.
`private boolean`	`currentLogFileHasUnflushedRecord()`
`long`	`getInstant()`	Return the log instant (as an integer) the scan is currently on - this is the log instant of the log record that was returned by getNextRecord.
`LogInstant`	`getLogInstant()`	Return the log instant the scan is currently on - this is the log instant of the log record that was returned by getNextRecord.
`long`	`getLogRecordEnd()`	Get the log instant that is right after the record just retrived
`LogRecord`	`getNextRecord(ArrayInputStream input, TransactionId tranId, int groupmask)`	Read a log record into the byte array provided.
`boolean`	`isLogEndFuzzy()`	returns true if there is partially writen log records before the crash in the last log file.
`private boolean`	`positionToNextRecord()`
`void`	`resetPosition(LogInstant instant)`	Reset the scan to the given LogInstant.
`private void`	`setCurrentLogFileFirstUnflushedPosition()`
`private void`	`setFirstUnflushed()`
`private void`	`switchLogFile()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - scan
```
private StorageRandomAccessFile scan
```
  - logFactory
```
LogToFile logFactory
```
  - open
```
boolean open
```
  - currentLogFileNumber
```
long currentLogFileNumber
```
  - currentLogFileFirstUnflushedPosition
```
long currentLogFileFirstUnflushedPosition
```
  - currentInstant
```
long currentInstant
```
  - firstUnflushed
```
long firstUnflushed
```
  - firstUnflushedFileNumber
```
long firstUnflushedFileNumber
```
  - firstUnflushedFilePosition
```
long firstUnflushedFilePosition
```
  - LOG_REC_LEN_BYTE_LENGTH
```
static final int LOG_REC_LEN_BYTE_LENGTH
```
    See Also:
    
    Constant Field Values
  - nextRecordLength
```
int nextRecordLength
```
    The length of the next record. Read from scan and set by currentLogFileHasUnflushedRecord. This is used to retain the length of a log record in the case currentLogFileHasUnflushedRecord reads the length and determines that some bytes in the log record are not yet flushed.
  - readNextRecordLength
```
boolean readNextRecordLength
```
    Flag to indicate that the length of the next log record has been read by currentLogFileHasUnflushedRecord. This flag gets reset in two ways:
    1. currentLogFileHasUnflushedRecord determines that the entire log record is flushed and returns true. In this case getNextRecord reads and returns the log record.
    2. we switch log files --due to a partial log record at the end of an old log file.
- Constructor Detail
  - FlushedScan
```
public FlushedScan(LogToFile logFactory,
                   long startAt)
            throws StandardException
```
    Throws:
    
    StandardException
- Method Detail
  - getNextRecord
```
public LogRecord getNextRecord(ArrayInputStream input,
                               TransactionId tranId,
                               int groupmask)
                        throws StandardException
```
    Read a log record into the byte array provided. Resize the input stream byte array if necessary.
    
    Specified by:
    
    getNextRecord in interface StreamLogScan
    
    Parameters:
    
    input - the ArrayInputStream to put the log record
    
    tranId - if non-null, only log record that equals tranId will be returned. If null, log records are not filtered on transaction Id.
    
    groupmask - if non-zero, only log record whose Loggable's group value is included in the groupmask is returned. groupmask can be a bit wise OR of many Loggable groups. If zero, log records are not filtered on the Loggable's group.
    
    Returns:
    
    the length of the data written into data, or -1 if the end of the scan has been reached.
    
    Throws:
    
    StandardException - Standard Derby error policy
  - resetPosition
```
public void resetPosition(LogInstant instant)
                   throws java.io.IOException
```
    Reset the scan to the given LogInstant.
    
    Specified by:
    
    resetPosition in interface StreamLogScan
    
    Parameters:
    
    instant - the position to reset to
    
    Throws:
    
    java.io.IOException - scan cannot access the log at the new position.
  - getLogRecordEnd
```
public long getLogRecordEnd()
```
    Get the log instant that is right after the record just retrived
    
    Specified by:
    
    getLogRecordEnd in interface StreamLogScan
    
    Returns:
    
    INVALID_LOG_INSTANT if this is not a FORWARD scan or, no record have been returned yet or the scan has completed.
  - isLogEndFuzzy
```
public boolean isLogEndFuzzy()
```
    returns true if there is partially writen log records before the crash in the last log file. Partiall wrires are identified during forward scans for log recovery.
    
    Specified by:
    
    isLogEndFuzzy in interface StreamLogScan
    
    Returns:
    
    true if fuzzy log end found during forward scan, this happens if there was a partially written log records before the crash.
  - getInstant
```
public long getInstant()
```
    Return the log instant (as an integer) the scan is currently on - this is the log instant of the log record that was returned by getNextRecord.
    
    Specified by:
    
    getInstant in interface StreamLogScan
    
    Returns:
    
    INVALID_LOG_INSTANT if no records have been returned yet or the scan has completed.
  - getLogInstant
```
public LogInstant getLogInstant()
```
    Return the log instant the scan is currently on - this is the log instant of the log record that was returned by getNextRecord.
    
    Specified by:
    
    getLogInstant in interface StreamLogScan
    
    Returns:
    
    null if no records have been returned yet or the scan has completed.
  - close
```
public void close()
```
    Close the scan.
    
    Specified by:
    
    close in interface StreamLogScan
  - setFirstUnflushed
```
private void setFirstUnflushed()
                        throws StandardException,
                               java.io.IOException
```
    Throws:
    
    StandardException
    
    java.io.IOException
  - setCurrentLogFileFirstUnflushedPosition
```
private void setCurrentLogFileFirstUnflushedPosition()
                                              throws java.io.IOException
```
    Throws:
    
    java.io.IOException
  - switchLogFile
```
private void switchLogFile()
                    throws StandardException
```
    Throws:
    
    StandardException
  - currentLogFileHasUnflushedRecord
```
private boolean currentLogFileHasUnflushedRecord()
                                          throws java.io.IOException
```
    Throws:
    
    java.io.IOException
  - positionToNextRecord
```
private boolean positionToNextRecord()
                              throws StandardException,
                                     java.io.IOException
```
    Throws:
    
    StandardException
    
    java.io.IOException

Class FlushedScan

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

scan

logFactory

open

currentLogFileNumber

currentLogFileFirstUnflushedPosition

currentInstant

firstUnflushed

firstUnflushedFileNumber

firstUnflushedFilePosition

LOG_REC_LEN_BYTE_LENGTH

nextRecordLength

readNextRecordLength

Constructor Detail

FlushedScan

Method Detail

getNextRecord

resetPosition

getLogRecordEnd

isLogEndFuzzy

getInstant

getLogInstant

close

setFirstUnflushed

setCurrentLogFileFirstUnflushedPosition

switchLogFile

currentLogFileHasUnflushedRecord

positionToNextRecord