Work of art – the intra query parallelism deadlock graphs

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Look at some of the graphs produced by the intra query parallelism deadlocks, below.

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Bart Duncan explains this “phenomenon” (bug, rather) in this article.

The two solutions to this problem are:

  • Adding or tuning an index in order to reduce the cost of the query and hence, eliminate parallelism
  • Using “OPTION (MAXDOP 1)” query hint to force-stop the query from parallelising

In some instances, depending on the optimization level for the query (specifically, TIMEOUT), you may be able to influence the execution plan by changing the order of the joins.

Would be interested to know if any of you have encountered this scenario and what you did to resolve the issue.

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