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Getting Started with Amazon Redshift by Stefan Bauer

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Query optimizer

The final section of this chapter is to start looking at the query optimizer. We will review execution plans further in the next chapter as we look at querying your data, so for now we will look at things in general terms. The Redshift optimizer, or "query planner", just like most modern-day query optimizers, will go through a number of steps relative to the query that was passed in for execution. Much of the optimization, such as removing unnecessary joins and columns, rewriting correlated subqueries, and so on, is around rewriting the query to obtain the fastest result possible. Don't worry, the optimizer will not change what you are asking, just how it is being asked. In this case, the optimizer is also aware of the number of ...

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