Concepts and capabilities of query parallelism


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SQL Server - concepts of query parallelism

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SQL Server - concepts of query parallelism - Feb 27, 2010 at 11:50 AM by Shuchi Gauri

Explain the concepts and capabilities of query parallelism.

SQL Server has the capability to process queries in parallel to optimize query execution and index operations for machines that have more than one microprocessor. This allows operations to be completed quickly and efficiently. SQL Server looks for queries/index operations that benefit from parallel execution while query optimization. For such queries, it inserts exchange operators into query execution plan to prepare the query for parallel execution. This operator provides process management, data redistribution and flow control.

A parallel execution plan can use more than a single thread which is determined at query plan execution initialization and is known by complexity of the plan and the degree of parallelism. Degree of parallelism determines number of microprocessors that are being used, it can be changed by using sp_configure stored procedure.

SQL Server - concepts of query parallelism - May 05, 2009 at 22:00 PM by Rajmeet Ghai

Explain the concepts and capabilities of query parallelism. 

Parallelism is the process of executing queries in parallel to increase performance.

Parallelism can be either inter query parallelism or intra query parallelism. In the former, the database accepts queries from multiple applications at the same time. Intra query parallelism is execution of the same query in parts. Parallel queries are most commonly used in decision support systems and data warehousing.

SQL Server - concepts of query parallelism - June 21, 2009 at 09:00 AM by Amit Satpute

Explain the concepts and capabilities of query parallelism.

Types of query parallelism:

1. Interquery parallelism:

  • Database can accept queries from multiple applications at the same time.
  • Each query runs independently of the others and at the same time.

2. Intraquery parallelism

  • Simultaneous processing of parts of a single query using intrapartition parallelism, interpartition parallelism, or both.

a) Intrapartition parallelism

  • Query is broken into multiple parts.

b) Interpartition parallelism

  • Query is broken into multiple parts across multiple partitions of a partitioned database, on one machine or multiple machines.
  • The query is run in parallel.


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