org.apache.derby.impl.store.raw.log

Class FlushedScan

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
        

Constructor Summary

Constructors

Constructor and Description
FlushedScan(LogToFile logFactory, long startAt)

Method Summary

Modifier and Type	Method and Description
void	close() Close the scan.
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.
void	resetPosition(LogInstant instant) Reset the scan to the given LogInstant.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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