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  • Incorrect Results Caused By Adding an Index

    It’s not often that a SQL Server bug really surprises me or makes me wonder how it was never spotted before, but this is one of those. To get right into it, say you have the following two tables: CREATE PARTITION FUNCTION PF (integer) AS RANGE RIGHT FOR VALUES (1000, 2000, 3000, 4000, 5000);   ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on August 20, 2013
  • Execution Plan Analysis: The Mystery Work Table

    I love SQL Server execution plans. It is often easy to spot the cause of a performance problem just by looking at one. The task is considerably easier if the plan includes run-time information (a so-called ‘actual’ execution plan), but even a compiled plan can be very useful. Nevertheless, there are still times where the execution plan does not ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on March 7, 2013
  • Optimizing T-SQL queries that change data

    Most tuning efforts for data-changing operations concentrate on the SELECT side of the query plan. Sometimes people will also look at important storage engine considerations like locking and transaction log throughput that can have dramatic effects. As a consequence, a number of common practices have emerged, such as avoiding large numbers of ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on January 25, 2013
  • Query Optimizer Deep Dive - Part 4

    This is the final part in a series of posts based on the content of the Query Optimizer Deep Dive presentations I have given over the last month or so at the Auckland SQL Users’ Group and the SQL Saturday events in Wellington, New Zealand and Adelaide, Australia. Links to other parts of this series: Part 1 Part 2 Part 3 Beating the Optimizer ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on April 30, 2012
  • Query Optimizer Deep Dive – Part 3

    This is the third part in a series of posts based on the content of the Query Optimizer Deep Dive presentations I have given over the last month or so at the Auckland SQL Users’ Group and the SQL Saturday events in Wellington, New Zealand and Adelaide, Australia. Links to other parts of this series: Part 1 Part 2 Part 4 Storage of Alternative ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on April 29, 2012
  • Query Optimizer Deep Dive – Part 2

    This is the second part in a series of posts based on the content of the Query Optimizer Deep Dive presentations I have given over the last month or so at the Auckland SQL Users’ Group and the SQL Saturday events in Wellington, New Zealand and Adelaide, Australia. Links to other parts of this series: Part 1 Part 3 Part 4 Cost-Based Optimization ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on April 28, 2012
  • Query Optimizer Deep Dive - Part 1

    This is the first in a series of posts based on the content of the Query Optimizer Deep Dive presentations I have given over the last month or so at the Auckland SQL Users’ Group and the SQL Saturday events in Wellington, New Zealand and Adelaide, Australia. Links to other parts of this series: Part 2 Part 3 Part 4 Introduction The motivation ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on April 27, 2012
  • Forcing a Parallel Query Execution Plan

    This post is for SQL Server developers who have experienced the special kind of frustration, which only comes from spending hours trying to convince the query optimizer to generate a parallel execution plan.  This situation often occurs when making an apparently innocuous change to the text of a moderately complex query; a change which ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on December 22, 2011
  • Inside the Optimizer: Constructing a Plan – Part 4

    Summary: More undocumented ways to explore how the query optimiser works. This post is part of a series: Part1 Part 2 Part3 Part4 Documented Rule-Affecting Options It might surprise you to learn that most T-SQL users have written queries that disable one or more of the optimiser rules already. Join hints { LOOP | HASH | MERGE | ...
    Posted to Paul White: Page Free Space (Weblog) by Paul White on July 31, 2010
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