internal FileLogRecord(FileLogRecordStream stream)
{
this.stream = stream;
}
// During WriteRestarArea, we truncate all records before the new base sequence number.
// The new base sequence number is recorded in the restart-area record.
// If truncate failed during WriteRestartArea, then the records before the new base seq number
// will still be present in the log. During recovery, we will cleanup the log by removing these records.
// Recovery steps -
// Scan the log backwards
// Stop when the last restart area is found
// Truncate the log if needed
private void Recover()
{
SequenceNumber first;
SequenceNumber last;
this.log.GetLogLimits(out first, out last);
// Internal knowledge - if last < first, log is empty
if (last < first)
return;
SequenceNumber sn = last;
while (sn != SequenceNumber.Invalid && first <= sn && sn <= last)
{
FileLogRecordStream stream = new FileLogRecordStream(log, sn);
if (stream.Header.IsRestartArea)
{
this.lastRestartArea = stream.RecordSequenceNumber;
// if the base sequence number is different from
// the next undo lsn, then we crashed during or
// before truncate. Perform the truncate now.
if (first < stream.Header.NextUndoLsn)
{
if (stream.Header.NextUndoLsn == SequenceNumber.Invalid)
{
// WriteRestartArea was called with LastSequenceNumber
if (first != stream.RecordSequenceNumber)
{
this.newBaseSeqNum = stream.RecordSequenceNumber;
}
}
else
{
this.newBaseSeqNum = stream.Header.NextUndoLsn;
}
// This method is called from the constructor. So no need to take a write lock.
if (this.newBaseSeqNum != SequenceNumber.Invalid)
{
try
{
log.TruncatePrefix(this.newBaseSeqNum);
this.newBaseSeqNum = SequenceNumber.Invalid;
}
#pragma warning suppress 56500
catch (Exception exception)
{
// Truncate failed again. We were unable to cleanup the log.
this.truncateFailed = true;
if (Fx.IsFatal(exception)) throw;
}
}
}
break;
}
sn = stream.PrevLsn;
}
}
internal FileLogRecord(FileLogRecordStream stream)
{
this.stream = stream;
}
public bool MoveNext()
{
if (this.disposed)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(Error.ObjectDisposed());
}
if (this.current == SequenceNumber.Invalid)
{
return(false);
}
if (!this.enumStarted)
{
this.enumStarted = true;
}
else
{
switch (this.logRecordEnum)
{
case LogRecordEnumeratorType.Next:
this.current = this.stream.NextLsn;
break;
case LogRecordEnumeratorType.Previous:
this.current = this.stream.Header.PreviousLsn;
break;
case LogRecordEnumeratorType.User:
this.current = this.stream.Header.NextUndoLsn;
break;
}
}
SequenceNumber first;
SequenceNumber last;
log.GetLogLimits(out first, out last);
if (this.current < first ||
last < this.current ||
this.current == SequenceNumber.Invalid)
{
this.record = null;
return(false);
}
this.stream = new FileLogRecordStream(this.log, this.current);
if (!this.enumRestartAreas && this.stream.Header.IsRestartArea)
{
if (this.logRecordEnum == LogRecordEnumeratorType.Next)
{
// Move to the next record after restart area.
return(MoveNext());
}
else
{
// We have hit a restart area.
// Restart areas have special values for prev and next undo in the header.
// Cannot enumerate further.
this.record = null;
return(false);
}
}
this.record = new FileLogRecord(this.stream);
return(true);
}
// During WriteRestarArea, we truncate all records before the new base sequence number.
// The new base sequence number is recorded in the restart-area record.
// If truncate failed during WriteRestartArea, then the records before the new base seq number
// will still be present in the log. During recovery, we will cleanup the log by removing these records.
// Recovery steps -
// Scan the log backwards
// Stop when the last restart area is found
// Truncate the log if needed
private void Recover()
{
SequenceNumber first;
SequenceNumber last;
this.log.GetLogLimits(out first, out last);
// Internal knowledge - if last < first, log is empty
if (last < first)
{
return;
}
SequenceNumber sn = last;
while (sn != SequenceNumber.Invalid && first <= sn && sn <= last)
{
FileLogRecordStream stream = new FileLogRecordStream(log, sn);
if (stream.Header.IsRestartArea)
{
this.lastRestartArea = stream.RecordSequenceNumber;
// if the base sequence number is different from
// the next undo lsn, then we crashed during or
// before truncate. Perform the truncate now.
if (first < stream.Header.NextUndoLsn)
{
if (stream.Header.NextUndoLsn == SequenceNumber.Invalid)
{
// WriteRestartArea was called with LastSequenceNumber
if (first != stream.RecordSequenceNumber)
{
this.newBaseSeqNum = stream.RecordSequenceNumber;
}
}
else
{
this.newBaseSeqNum = stream.Header.NextUndoLsn;
}
// This method is called from the constructor. So no need to take a write lock.
if (this.newBaseSeqNum != SequenceNumber.Invalid)
{
try
{
log.TruncatePrefix(this.newBaseSeqNum);
this.newBaseSeqNum = SequenceNumber.Invalid;
}
#pragma warning suppress 56500
catch (Exception exception)
{
// Truncate failed again. We were unable to cleanup the log.
this.truncateFailed = true;
if (Fx.IsFatal(exception))
{
throw;
}
}
}
}
break;
}
sn = stream.PrevLsn;
}
}
