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Wednesday, March 18, 2009 7:34 AM

OPTIMIZED Nested Loops Joins

In my past two posts, I explained how SQL Server may add a sort to the outer side of a nested loops join and showed how this sort can significantly improve performance . In an earlier post , I discussed how SQL Server can use random prefetching to improve
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Wednesday, March 04, 2009 9:27 AM

Optimizing I/O Performance by Sorting – Part 2

In my last post, I discussed how SQL Server can use sorts to transform random I/Os into sequential I/Os. In this post, I'll demonstrate directly how such a sort can impact performance. For the following experiments, I'll use the same 3 GByte database
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Wednesday, February 25, 2009 9:29 AM

Optimizing I/O Performance by Sorting – Part 1

In this post from last year, I discussed how random I/Os are slower than sequential I/Os (particularly for conventional rotating hard drives). For this reason, SQL Server often favors query plans that perform sequential scans of an entire table over plans
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Tuesday, October 07, 2008 2:44 PM

Random Prefetching

In my last post , I explained the importance of asynchronous I/O and described how SQL Server uses sequential read ahead to boost the performance of scans. In this post, I'll discuss how SQL Server uses random prefetching. Let's begin with a simple example
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