Indexes

Sifiso W. Ndlovu

How to use Columnstore Indexes to improve your Data Warehouse Staging Environment

May 4, 2017 by

My team and I were recently tasked with refactoring older data marts, particularly those that were created with SQL Server 2008 in mind. As we all know, SQL Server has undergone significant changes since the release of SQL Server 2008. One of those changes relates to the introduction of columnstore as an alternative to the traditional B-tree index (rowstore). Whilst most of the existing documentation relating to columnstore seem to focus on the benefit of columnstore against data warehouse workloads, in this article I argue that the usage of columnstore index should not be limited to facts and dimensions instead let’s introduce it in our data warehouse staging environments too.

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Simon Liew

The impact of Residual Predicates in a SQL Server Index Seek operation

March 6, 2017 by

Abstract

It is common assumption that an Index Seek operation in a query plan is optimal when returning a low number of output rows. In a scenario involving residual predicates, an Index Seek operation could be reading a lot more rows than it needs into the memory, then each row is evaluated and discarded in memory based on the residual predicate and returns low number of output rows.

This article will explain the concept and the impact of Residual Predicates in a SQL Server Index Seek operation.

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Ahmad Yaseen

Indexing SQL Server temp tables

January 31, 2017 by

SQL Server temp tables are a special type of tables that are written to the TempDB database and act like regular tables, providing a suitable workplace for intermediate data processing before saving the result to a regular table, as it can live only for the age of the database connection.

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Gerald Britton

Options for Partitioned Tables and Indexes in SQL Server

January 31, 2017 by

Introduction

I work for a large, multinational financial institution. Like most companies in this field, ours is conservative and subject to much regulatory oversight. The first has meant that we’re slow to adopt new technologies. We need to be really, really, really sure things won’t break, customer accounts won’t vanish or lose their balances and that the regulators will not raise any red flags. Everything we do is subject to the scrutiny of our internal auditors, even something that seems simple, like rerunning a production job that failed because the host compute was down. I really mean everything!

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Kimberly Killian

SQL Server Index vs Statistics a consultants woes…or rants

December 29, 2016 by

As a DBA, I am often asked why is something performing slow, what and why statistics need to be updated or what will cause them to be “off”. My initial question to clients when they pose these questions to me is what changed on your end? Did the data change significantly and did the rebuild or reorganize index job run? Before I get into the answers to these questions from my clients, let me give you some background. So, just to clarify, for most of my clients, I work as a remote part-time DBA, that being said, I manage their database from every aspect including setting up servers, backups/restore, troubleshooting, managing their index’s, etc. and again remotely. So normally, I have setup jobs that will manage their index’s ranging from a weekly rebuild or even sometimes I use one that I’ve designed that makes a choice to either rebuild or reorganize an index based on fragmentation level. The “general rule of thumb” is reorganizing the index for fragmentation from 5% to 29% and rebuild when 30% plus. Those are pretty standard numbers I did not make them up.

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Ahmad Yaseen

SQL Server 2014 Columnstore index

April 29, 2016 by

By default, SQL Server stores data logically in the tables as rows and columns, which appear in the result grid while retrieving data from any table and physically in the disk in the row-store format inside the data pages. A new data store mechanism introduced in SQL Server 2012, based on xVelocity in-memory technology, in which the data is stored in the column-store data format. This data store mechanism called the Columnstore index.

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Kimberly Killian

What is causing database slowdowns?

February 2, 2016 by

Why is my database so slow? This query used to be so much faster. Why does it take so long to rebuild my index? How come it was fine last month? Every day I am asked these types of questions by clients. Every day! A lot of database developers and application developers do not realize that indexes are ever changing entities within your database or rather they need to be monitored closely and managed periodically to remain efficient. I cannot even count the times someone tells me “but we have index’s on this or that column and it was fine last month” and so on. All while they fail to realize or even tell me that the database just took on, updated or deleted 1,000,000 records for example, which would definitely change the footprint of the data, making the index’s unsound or in need of help. Even adding 50 new users that use the data differently could require new indexes. That being said, I decided to automate a quick and easy data gathering and reporting job that helps to answer these questions. Most of the time query performance questions can be answered by determining the fragmentation levels of index’s, if there are missing index’s, duplicate index’s, unused index’s and what are the heavy hitters in regards to queries and are queries running in memory or to disk and how many executions. My favorite thing to do with SQL Server is automate, automate and automate the tasks that are asked of me over and over.

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Miroslav Dimitrov

Tips and tricks for SQL Server database maintenance optimization

January 11, 2016 by

Database maintenance is very important, a critical part of our database administrators’ daily tasks. However, this aspect is frequently underestimated which could lead to performance problems and respectively angry, unhappy customers. In this article, we will take a look at the different maintenance operations we have in SQL Server and how we can optimize them and take the maximum out of each.

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Ed Pollack

Filtered indexes: Performance analysis and hidden costs

December 11, 2015 by

Introduction

Filtered indexes are well documented, as they have been around in SQL Server for almost six years now. Despite their longevity and usefulness, discussions of them tend to be very simple overviews using simple queries and not digging too deeply into more precise costs and benefits. This article is inspired by a production problem that cropped up recently involving a filtered index that illustrated that general knowledge of their function was not as complete as it should have been.

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Daniel Calbimonte

DTA, a great tool to automate indexes

December 4, 2015 by

Introduction

In a previous chapter, we learned how to use the Tuning Advisor to analyze queries and receive recommendations about indexes, partitions and statistics. In this new chapter, we will learn how to use the command line tool called DTA. The DTA is the command line of the Tuning Advisor.

The DTA is a very powerful tool that can be used to automate some tuning tasks. It can be used combined with the SQL Agent, SSIS, or customized and external tools like programs made in C# or Java.

In this article, we will show how to use this tool.

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Daniel Calbimonte

A great tool to create SQL Server indexes

December 1, 2015 by

Introduction

The indexes in many cases are great solutions to solve performance problems. For some problems, they are magical and very cheap solutions. In this chapter, we will show a demo of the SQL Server Tuning Advisor, which is a tool that comes with the SQL Server Installation. We will also use the SQL Server Profiler to generate the information for the Tuning Advisor.

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Sifiso W. Ndlovu

Columnstore Index in SQL Server

May 28, 2014 by

Prerequisite

The discussion pertaining to SQL Server 2012 columnstore indexing is better explained through theoretical and practical measures. Thus, for the practical measure part – I will be using the AdventureWorksDW2012 sample database. The rest of the prerequisites for a comprehensive understanding of this topic are as follows:
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Milena Petrovic

Frequent query recompilations – a SQL query performance killer – detection

April 11, 2014 by
In the previous part of this article, we presented query recompilation basics. We explained when a query is compiled, when recompiled, and what preferred behavior is. We also showed the how to trigger a recompilation using T-SQL and provided examples. In this part, we will focus on detecting frequent query recompilations and frequently recompiled queries. Read more »