| Id | Operation | Name | Rows | Bytes | TQ |IN-OUT| PQ Distrib | The number of parallel execution servers in one set is the degree of parallelism (DOP).Įxample 8-2 Explain Plan Output for a Query on Customers and Sales The coordinator must decide whether an operation can be performed in parallel and, if so, how many parallel execution servers to enlist. For example, the parallel execution method might be to perform a parallel full table scan by block range or a parallel index range scan by partition. For example, a parallel query with a SUM() operation requires adding the individual subtotals calculated by each parallel server.įinally, the query coordinator returns any results to the user.Īfter the optimizer determines the execution plan of a statement, the parallel execution coordinator determines the parallel execution method for each operation in the plan. When the parallel servers are finished executing the statement, the query coordinator performs any portion of the work that cannot be executed in parallel. The parallel execution servers performs each operation in parallel if possible. The SQL statement is executed as a sequence of operations (a full table scan to perform a join on a nonindexed column, an ORDER BY clause, and so on). The query coordinator obtains the necessary number of parallel servers. The user session or shadow process takes on the role of a coordinator, often called the query coordinator. If parallel execution is chosen, then the following steps occur: Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Each SQL statement undergoes an optimization and parallelization process when it is parsed.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.
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