private bool WriteItems(
RequestExecutionContext context, RequestExecutionBuffer buffer, IDriverDataEnumerator sourceEnumerator, bool havePendingDriverRow)
{
// have to check for disposal here, because this method gets invoked in a loop
if (m_disposed)
{
buffer.Error = new ObjectDisposedException("This data engine has been disposed");
return false;
}
if (sourceEnumerator == null)
{
return false;
}
var stream = buffer.Stream;
var writer = buffer.Writer;
var cts = context.CancellationTokenSource;
buffer.RowsOutput = 0;
var hasPendingWrite = false;
var mustReturnDataset = context.Request.ReturnDataset;
var lastValidLength = stream.Length;
var totalRowsProduced = context.TotalRowsProduced;
var recordsAffected = context.RecordsAffected;
var rowsOutputLocally = 0;
var func = context.ParsedRequest.BaseDataset.Paging.Offset;
var pagingOffset = ReferenceEquals(func, null) ? 0 : func(context.ParsedRequest.Params.InputValues);
func = context.ParsedRequest.BaseDataset.Paging.PageSize;
var pageSize = ReferenceEquals(func, null) ? Int32.MaxValue : func(context.ParsedRequest.Params.InputValues);
// one row might not have fit into previous buffer, let's write it now
if (havePendingDriverRow)
{
try
{
// no need to apply paging and where clause for pending row: we applied them already
// also expect that a buffer can accomodate at least one row
// - this requires that rows are never larger than RequestExecutionBuffer.MaxBytesPerBuffer
ProduceOutputRow(context);
context.OutputDataBuffer.Write(writer);
rowsOutputLocally++;
lastValidLength = stream.Length;
}
catch (Exception e)
{
throw new Exception("Internal buffer may be too small to fit even a single data row", e);
}
}
// now let's deal with remaining items in the enumerator
while (lastValidLength < RequestExecutionBuffer.MaxBytesPerBuffer && !cts.IsCancellationRequested)
{
if (recordsAffected >= pageSize || !sourceEnumerator.MoveNext())
{
// enough rows accumulated, or no more rows from driver: halt
break;
}
// if record satisfies WHERE criteria, it gets counted into pre-paging total
if (ApplyWhereClause(context))
{
var isAccumulating = totalRowsProduced >= pagingOffset;
totalRowsProduced++;
if (isAccumulating)
{
// once WHERE has been evaluated, read all remaining fields for this row into the buffer
sourceEnumerator.FetchAdditionalFields();
// output row number is needed for "rownumoutput()" Pql function
context.ClauseEvaluationContext.RowNumberInOutput = recordsAffected;
// increment counter BEFORE producing and writing
// even if we fail to write into current buffer, we'll write into next one
recordsAffected++;
// this will be false when clients do ExecuteNonQuery or Prepare
if (mustReturnDataset)
{
// produce SELECT (output scheme) from FROM (raw data from storage driver)
var estimatedSize = ProduceOutputRow(context);
if (lastValidLength + estimatedSize > RequestExecutionBuffer.MaxBytesPerBuffer)
{
// store pending write and return
hasPendingWrite = true;
break;
}
// MemoryStream will throw NotSupportedException when trying to expand beyond fixed buffer size
// this should never happen (see check above)
context.OutputDataBuffer.Write(writer);
// this counter gets incremented AFTER writing,
// because it indicates how many rows have in fact been put into current block
rowsOutputLocally++;
}
lastValidLength = stream.Length;
}
// row number is needed for "rownum()" Pql function
context.ClauseEvaluationContext.RowNumber++;
}
}
buffer.RowsOutput = rowsOutputLocally;
context.RecordsAffected = recordsAffected;
context.TotalRowsProduced = totalRowsProduced;
stream.Seek(0, SeekOrigin.Begin);
return hasPendingWrite;
}
private void StartProduction(
RequestExecutionContext context, RequestExecutionBuffer buffer, out IDriverDataEnumerator sourceEnumerator)
{
ReadRequest(context);
context.AttachContainerDescriptor(m_containerDescriptor);
if (!context.CacheInfo.HaveParsingResults)
{
lock (context.CacheInfo)
{
context.CacheInfo.CheckIsError();
if (!context.CacheInfo.HaveParsingResults)
{
try
{
ParseRequest(context.Request, context.RequestBulk, context.CacheInfo.ParsedRequest, context.CancellationTokenSource.Token);
CompileClauses(context.ContainerDescriptor, context.CacheInfo);
Thread.MemoryBarrier();
context.CacheInfo.HaveParsingResults = true;
}
catch (Exception e)
{
// make sure that partially complete results do not become visible
context.CacheInfo.IsError(e);
throw;
}
}
}
}
context.CacheInfo.WriteParsingResults(context.ParsedRequest);
if (context.ParsedRequest.SpecialCommand.IsSpecialCommand)
{
sourceEnumerator = null;
ExecuteSpecialCommandStatement(context, buffer);
return;
}
// structure of output buffer depends on which fields client is asking for
// therefore, we re-create and re-attach a driver output buffer for every request
context.AttachDriverOutputBufferAndInputParameters(
QueryParser.CreateDriverRowDataBuffer(context.ParsedRequest.BaseDataset.BaseFields),
context.ParsedRequest);
// this enumerator will yield our own driverOutputBuffer for every source record
// e.g. the very same context.DriverOutputBuffer is going to be yielded N times from this enumerator
if (context.ParsedRequest.StatementType == StatementType.Insert)
{
if (context.ParsedRequest.IsBulk)
{
sourceEnumerator = CreateInputDataEnumerator(context);
//m_storageDriver.AllocateCapacityForDocumentType(context.ParsedRequest.TargetEntity.DocumentType, context.RequestBulk.InputItemsCount);
}
else
{
sourceEnumerator = CreatePseudoEnumeratorForInsertValues(context);
}
}
else
{
if (context.ParsedRequest.IsBulk)
{
// for SELECT and DELETE, we only use PK values from the input enumerator
// for UPDATE, we use both PK values and other field values from input enumerator
context.AttachInputDataEnumerator(CreateInputDataEnumerator(context));
}
// driver returns set of rows related to given set of PK values
// for a bulk request, sourceEnumerator will yield exactly one item for each item in input enumerator
sourceEnumerator = m_storageDriver.GetData(context);
}
switch (context.ParsedRequest.StatementType)
{
case StatementType.Select:
{
context.AttachResponseHeaders(CreateResponseSchemeForSelect(context));
context.PrepareBuffersForSelect();
context.ResponseHeaders.RecordsAffected = 0;
}
break;
case StatementType.Update:
{
context.AttachResponseHeaders(new DataResponse(0, "Update successful"));
context.PrepareBuffersForUpdate();
ExecuteInsertUpdateStatement(context, buffer, sourceEnumerator, DriverChangeType.Update);
context.ResponseHeaders.RecordsAffected = context.RecordsAffected;
}
break;
case StatementType.Delete:
{
context.AttachResponseHeaders(new DataResponse(0, "Delete successful"));
context.PrepareBuffersForDelete();
ExecuteDeleteStatement(context, buffer, sourceEnumerator);
context.ResponseHeaders.RecordsAffected = context.RecordsAffected;
}
break;
case StatementType.Insert:
{
context.AttachResponseHeaders(new DataResponse(0, "Insert successful"));
context.PrepareChangeBufferForInsert();
ExecuteInsertUpdateStatement(context, buffer, sourceEnumerator, DriverChangeType.Insert);
context.ResponseHeaders.RecordsAffected = context.RecordsAffected;
}
break;
default:
throw new Exception("Invalid statement type: " + context.ParsedRequest.StatementType);
}
}
private void ExecuteInsertUpdateStatement(RequestExecutionContext context, RequestExecutionBuffer buffer, IDriverDataEnumerator sourceEnumerator, DriverChangeType changeType)
{
if (sourceEnumerator == null)
{
return;
}
buffer.RowsOutput = 0;
var cts = context.CancellationTokenSource;
var updates = context.ParsedRequest.Modify.UpdateAssignments;
context.ClauseEvaluationContext.RowNumber = 0;
context.ClauseEvaluationContext.RowNumberInOutput = context.ClauseEvaluationContext.RowNumber;
var changeBuffer = context.ClauseEvaluationContext.ChangeBuffer;
var changeset = m_storageDriver.CreateChangeset(changeBuffer, context.ParsedRequest.IsBulk);
try
{
changeBuffer.ChangeType = changeType;
while (!cts.IsCancellationRequested && sourceEnumerator.MoveNext())
{
// if record satisfies WHERE criteria, compute updated values and give them to driver
if (ApplyWhereClause(context))
{
// make sure we have values for fields in SET expressions
sourceEnumerator.FetchAdditionalFields();
BitVector.SetAll(changeBuffer.Data.NotNulls, false);
for (var ordinal = 0; ordinal < updates.Count; ordinal++)
{
if (updates[ordinal].CompiledExpression != null)
{
updates[ordinal].CompiledExpression(context.ClauseEvaluationContext);
}
}
// this will either take internal entity id from current data row
// or from the computed change buffer data (for non-bulk inserts)
sourceEnumerator.FetchInternalEntityIdIntoChangeBuffer(changeBuffer, context);
m_storageDriver.AddChange(changeset);
}
// row number is needed for "rownum()" Pql function
context.ClauseEvaluationContext.RowNumber++;
// output row number is needed for "rownumoutput()" Pql function
context.ClauseEvaluationContext.RowNumberInOutput = context.ClauseEvaluationContext.RowNumber;
}
if (!cts.IsCancellationRequested)
{
context.RecordsAffected = m_storageDriver.Apply(changeset);
}
}
catch
{
m_storageDriver.Discard(changeset);
throw;
}
}
private void ExecuteSpecialCommandStatement(RequestExecutionContext context, RequestExecutionBuffer buffer)
{
switch (context.ParsedRequest.SpecialCommand.CommandType)
{
case ParsedRequest.SpecialCommandData.SpecialCommandType.Defragment:
context.AttachResponseHeaders(new DataResponse(0, "Defragmentation completed"));
m_storageDriver.Compact(CompactionOptions.FullReindex);
break;
default:
throw new ArgumentOutOfRangeException("context", context.ParsedRequest.SpecialCommand.CommandType, "Invalid special command");
}
}
private void ExecuteDeleteStatement(RequestExecutionContext context, RequestExecutionBuffer buffer, IDriverDataEnumerator sourceEnumerator)
{
if (sourceEnumerator == null)
{
return;
}
buffer.RowsOutput = 0;
var cts = context.CancellationTokenSource;
context.ClauseEvaluationContext.RowNumber = 0;
context.ClauseEvaluationContext.RowNumberInOutput = context.ClauseEvaluationContext.RowNumber;
var changeBuffer = context.ClauseEvaluationContext.ChangeBuffer;
var changeset = m_storageDriver.CreateChangeset(changeBuffer, context.ParsedRequest.IsBulk);
try
{
changeBuffer.ChangeType = DriverChangeType.Delete;
while (!cts.IsCancellationRequested && sourceEnumerator.MoveNext())
{
// if record satisfies WHERE criteria, compute updated values and give them to driver
if (ApplyWhereClause(context))
{
// load internal ID, it is needed
sourceEnumerator.FetchAdditionalFields();
sourceEnumerator.FetchInternalEntityIdIntoChangeBuffer(changeBuffer, context);
m_storageDriver.AddChange(changeset);
}
// row number is needed for "rownum()" Pql function
context.ClauseEvaluationContext.RowNumber++;
// output row number is needed for "rownumoutput()" Pql function
context.ClauseEvaluationContext.RowNumberInOutput = context.ClauseEvaluationContext.RowNumber;
}
if (!cts.IsCancellationRequested)
{
context.RecordsAffected = m_storageDriver.Apply(changeset);
}
}
catch
{
m_storageDriver.Discard(changeset);
throw;
}
}