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FT_IFTSHC_MUTEX

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Description:

This wait is when a thread that is participating in a full-text operation is waiting for synchronization with other full-text worker threads.

(Books Online description: “Full-text is waiting on an fdhost control operation. Documented for informational purposes only. Not supported. Future compatibility is not guaranteed.”)

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Added in SQL Server version:

2008

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 585 in 2008 and 2008 R2, 635 in 2012, and 651 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

This wait type is one that I usually filter out as a benign wait when doing wait statistics analysis.

I have not seen this wait type be a noticeable contention point.

Known occurrences in SQL Server (list number matches call stack list):

  1. Waiting for synchronization (in this case, while participating in a crawl and sending a batch of full-text information to the central collection point)
  2. Waiting for synchronization (in this case, while waiting for an asynchronous read to complete)
  3. Waiting for synchronization (in this case, while waiting for an asynchronous write to complete)

And other similar call stacks.

Abbreviated call stacks (list number matches known occurrences list):

  1. SOS_Task::PostWait+6e
    EventInternal<SuspendQueueSLock>::Wait+23f
    SOS_Mutex::Wait+6f
    CLock::Request+39
    CSrchFDManager::SendBatch+22
    CSrchFDManagerCollection::SendBatchToFD+82
    CIFTSHostController::SendBatchToFD+1c
    CIFTSPipeline::OnDataChange+155
    CFTWICrawl::PrepareBatch+4fa
    CFTFullCrawl::ExecuteCrawl+1b6
    CFTWICrawl::ExecuteImpl+f9
    IFTSWorkerTask+214
    SystemTaskEntryPoint+331
    SOS_Scheduler::SystemTimerEntryPoint+bc
    SOS_Scheduler::SystemTimerInit+70
    SOS_Task::Param::Execute+292
    SOS_Scheduler::RunTask+a2
  2. SOS_Task::PostWait+6e
    EventInternal<SuspendQueueSLock>::Wait+23f
    CSrchPipeCallbackBase::Wait+2c
    CSrchAsyncWritePipe::ASyncReadIOWorker+4e
    PipeWorkerThreadEntry+29
    LaunchFTTaskWithContext+88
    SOS_Task::Param::Execute+292
    SOS_Scheduler::RunTask+a2
  3. SOS_Task::PostWait+6e
    EventInternal<SuspendQueueSLock>::Wait+23f
    CSrchPipeCallbackBase::Wait+2c
    CSrchAsyncWritePipe::ASyncWriteIOComplete+36
    PipeWorkerThreadEntry+29
    LaunchFTTaskWithContext+88
    SOS_Task::Param::Execute+292
    SOS_Scheduler::RunTask+a2