/// <summary>
/// Returns event records in the reverse sequence they were committed into TF.
/// Positions is specified as post-positions (pointer after the end of record).
/// </summary>
public ReadAllResult ReadAllEventsBackward(TFPos pos, int maxCount, bool resolveLinks)
{
var records = new List <ResolvedEventRecord>();
var nextPos = pos;
// in case we are at position after which there is no commit at all, in that case we have to force
// PreparePosition to 0, so if you decide to read backwards from PrevPos,
// you will receive all prepares.
var prevPos = new TFPos(pos.CommitPosition, 0);
var count = 0;
bool firstCommit = true;
ITransactionFileSequentialReader seqReader = GetSeqReader();
try
{
long nextCommitPostPos = pos.CommitPosition;
while (count < maxCount)
{
seqReader.Reposition(nextCommitPostPos);
SeqReadResult result;
do
{
result = seqReader.TryReadPrev();
}while (result.Success && result.LogRecord.RecordType != LogRecordType.Commit); // skip until commit
if (!result.Success) // no more records in TF
{
break;
}
var commitPostPos = result.RecordPostPosition;
nextCommitPostPos = result.RecordPrePosition;
var commit = (CommitLogRecord)result.LogRecord;
if (firstCommit)
{
firstCommit = false;
// for forward pass we allow read the same commit and as we have post-positions here
// we can put just prepare post-position as prepare pre-position for forward read
// so we put pre-position of commit and post-position of prepare
prevPos = new TFPos(commit.LogPosition, pos.PreparePosition);
}
// as we don't know exact position of the last record of transaction,
// we have to sequentially scan backwards, so no need to reposition
//seqReader.Reposition(commitLogRecord.TransactionPosition);
while (count < maxCount)
{
result = seqReader.TryReadPrev();
if (!result.Success) // no more records in TF
{
break;
}
// prepare with TransactionBegin could be scavenged already
// so we could reach beyond the start of transaction. In that case we have to stop.
if (result.LogRecord.Position < commit.TransactionPosition)
{
break;
}
if (result.LogRecord.RecordType != LogRecordType.Prepare)
{
continue;
}
var prepare = (PrepareLogRecord)result.LogRecord;
if (prepare.TransactionPosition != commit.TransactionPosition) // wrong prepare
{
continue;
}
if ((prepare.Flags & PrepareFlags.Data) != 0) // prepare with useful data
{
if (new TFPos(commitPostPos, result.RecordPostPosition) <= pos)
{
var eventRecord = new EventRecord(commit.EventNumber + prepare.TransactionOffset, prepare);
EventRecord linkToEvent = null;
if (resolveLinks)
{
var resolved = ResolveLinkToEvent(eventRecord);
if (resolved != null)
{
linkToEvent = eventRecord;
eventRecord = resolved;
}
}
records.Add(new ResolvedEventRecord(eventRecord, linkToEvent, commit.Position));
count++;
// for backward pass we allow read the same commit, but force to skip last read prepare
// so we put post-position of commit and pre-position of prepare
nextPos = new TFPos(commitPostPos, prepare.LogPosition);
}
}
if ((prepare.Flags & PrepareFlags.TransactionBegin) != 0)
{
break;
}
}
}
}
finally
{
ReturnSeqReader(seqReader);
}
return(new ReadAllResult(records, maxCount, pos, nextPos, prevPos));
}
private void ReturnSeqReader(ITransactionFileSequentialReader seqReader)
{
_seqReaders.Push(seqReader);
}
/// <summary>
/// Returns event records in the sequence they were committed into TF.
/// Positions is specified as pre-positions (pointer at the beginning of the record).
/// </summary>
public ReadAllResult ReadAllEventsForward(TFPos pos, int maxCount, bool resolveLinks)
{
var records = new List <ResolvedEventRecord>();
var nextPos = pos;
// in case we are at position after which there is no commit at all, in that case we have to force
// PreparePosition to int.MaxValue, so if you decide to read backwards from PrevPos,
// you will receive all prepares.
var prevPos = new TFPos(pos.CommitPosition, int.MaxValue);
var count = 0;
bool firstCommit = true;
ITransactionFileSequentialReader seqReader = GetSeqReader();
try
{
long nextCommitPos = pos.CommitPosition;
while (count < maxCount)
{
seqReader.Reposition(nextCommitPos);
SeqReadResult result;
do
{
result = seqReader.TryReadNext();
}while (result.Success && result.LogRecord.RecordType != LogRecordType.Commit); // skip until commit
if (!result.Success) // no more records in TF
{
break;
}
nextCommitPos = result.RecordPostPosition;
var commit = (CommitLogRecord)result.LogRecord;
if (firstCommit)
{
firstCommit = false;
// for backward pass we want to allow read the same commit and skip read prepares,
// so we put post-position of commit and post-position of prepare as TFPos for backward pass
prevPos = new TFPos(result.RecordPostPosition, pos.PreparePosition);
}
seqReader.Reposition(commit.TransactionPosition);
while (count < maxCount)
{
result = seqReader.TryReadNext();
if (!result.Success) // no more records in TF
{
break;
}
// prepare with TransactionEnd could be scavenged already
// so we could reach the same commit record. In that case have to stop
if (result.LogRecord.Position >= commit.Position)
{
break;
}
if (result.LogRecord.RecordType != LogRecordType.Prepare)
{
continue;
}
var prepare = (PrepareLogRecord)result.LogRecord;
if (prepare.TransactionPosition != commit.TransactionPosition) // wrong prepare
{
continue;
}
if ((prepare.Flags & PrepareFlags.Data) != 0) // prepare with useful data
{
if (new TFPos(commit.Position, prepare.LogPosition) >= pos)
{
var eventRecord = new EventRecord(commit.EventNumber + prepare.TransactionOffset, prepare);
EventRecord linkToEvent = null;
if (resolveLinks)
{
var resolved = ResolveLinkToEvent(eventRecord);
if (resolved != null)
{
linkToEvent = eventRecord;
eventRecord = resolved;
}
}
records.Add(new ResolvedEventRecord(eventRecord, linkToEvent, commit.Position));
count++;
// for forward pass position is inclusive,
// so we put pre-position of commit and post-position of prepare
nextPos = new TFPos(commit.LogPosition, result.RecordPostPosition);
}
}
if ((prepare.Flags & PrepareFlags.TransactionEnd) != 0)
{
break;
}
}
}
}
finally
{
ReturnSeqReader(seqReader);
}
return(new ReadAllResult(records, maxCount, pos, nextPos, prevPos));
}
private void ReturnSeqReader(ITransactionFileSequentialReader seqReader)
{
_seqReaders.Push(seqReader);
}