//-----------------------------------------------------------------------------------
// Creates and begins execution of a new spooling task. If pipelineMerges is specified,
// we will execute the task asynchronously; otherwise, this is done synchronously,
// and by the time this API has returned all of the results have been produced.
//
// Arguments:
// source - the producer enumerator
// destination - the destination channel into which to spool elements
// ordinalIndexState - state of the index of the input to the merge
//
// Assumptions:
// Source cannot be null, although the other arguments may be.
//
internal static void Spool(
QueryTaskGroupState groupState, PartitionedStream <TInputOutput, TKey> partitions,
Shared <TInputOutput[]> results, TaskScheduler taskScheduler)
{
Contract.Requires(groupState != null);
Contract.Requires(partitions != null);
Contract.Requires(results != null);
Contract.Requires(results.Value == null);
// Determine how many async tasks to create.
int maxToRunInParallel = partitions.PartitionCount - 1;
// Generate a set of sort helpers.
SortHelper <TInputOutput, TKey>[] sortHelpers =
SortHelper <TInputOutput, TKey> .GenerateSortHelpers(partitions, groupState);
// Ensure all tasks in this query are parented under a common root.
Task rootTask = new Task(
() =>
{
// Create tasks that will enumerate the partitions in parallel. We'll use the current
// thread for one task and then block before returning to the caller, until all results
// have been accumulated. Pipelining is not supported by sort merges.
for (int i = 0; i < maxToRunInParallel; i++)
{
TraceHelpers.TraceInfo("OrderPreservingSpoolingTask::Spool: Running partition[{0}] asynchronously", i);
QueryTask asyncTask = new OrderPreservingSpoolingTask <TInputOutput, TKey>(
i, groupState, results, sortHelpers[i]);
asyncTask.RunAsynchronously(taskScheduler);
}
// Run one task synchronously on the current thread.
TraceHelpers.TraceInfo("OrderPreservingSpoolingTask::Spool: Running partition[{0}] synchronously", maxToRunInParallel);
QueryTask syncTask = new OrderPreservingSpoolingTask <TInputOutput, TKey>(
maxToRunInParallel, groupState, results, sortHelpers[maxToRunInParallel]);
syncTask.RunSynchronously(taskScheduler);
});
// Begin the query on the calling thread.
groupState.QueryBegin(rootTask);
// We don't want to return until the task is finished. Run it on the calling thread.
rootTask.RunSynchronously(taskScheduler);
// Destroy the state associated with our sort helpers.
for (int i = 0; i < sortHelpers.Length; i++)
{
sortHelpers[i].Dispose();
}
// End the query, which has the effect of propagating any unhandled exceptions.
groupState.QueryEnd(false);
}
//-----------------------------------------------------------------------------------
// Schedules execution of the merge itself.
//
// Arguments:
// ordinalIndexState - the state of the ordinal index of the merged partitions
//
void IMergeHelper <TInputOutput> .Execute()
{
OrderPreservingSpoolingTask <TInputOutput, TKey> .Spool(_taskGroupState, _partitions, _results, _taskScheduler);
}
