Information about the cardinality and distribution of output values provided to Wrong decisions may also occur due to optimizer model limitations or inaccurate
#Mysql optimizer different results between servers serial
Run faster when using a parallel plan, although the Query Optimizer chooses to useĪ serial plan, due to the slight difference in the cost between the serial and parallel However, notĪll the query optimizer decisions are the best option and you may find that the query will Scalar or relational operators that cannot be run in parallel mode. Query using a serial plan, rather than using a parallel plan, due to the expensiveĬost of the parallel plan versus the serial plan, or because the query contains In some circumstances, the SQL Server Query Optimizer chooses to execute the Plan, the SQL Server Engine detects the number of CPUs required to execute the query,Ĭalled the Degree Of Parallelism (DOP), and distributes the tasks among these threads If the decision is taken to use a parallel Is less than the cost of a serial plan, then a parallel plan will be created and The Cost Threshold of Parallelism value and the cost of the parallel plan Setting is greater than 1 or 0 (if 0 all processors will be used) and the cost of the query exceeds That a serial plan will always be used to execute the query. Is configured to allow parallel plans where a MAXDOP with a value equal to 1 means The Maximum Degree of Parallelism (MAXDOP) Server Database Engine will check if the SQL Server instance is running on a server Query will run much faster than the serial plan.īefore choosing to execute the query using serial or a parallel plan, the SQL As a result of using a parallel plan, the
You can imagine a parallel plan as multiple serial plans that run at the That run simultaneously, where each task will accomplish part of the overall job.įinally, the partial results of each small task will be combined into one final Parallelism is the process of splitting a big task into multiple smaller tasks
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