In the previous articles of this series (see bottom for a full index), we described, in detail, the structure of SQL Server tables and indexes, the basics and guidelines that help us in designing a proper index and finally the list of operations that can be performed on the SQL Server indexes. In this article, […]
SQL Server 2017 brings a new query processing methods that are designed to mitigate cardinality estimation errors in query plans and adapt plan execution based on the execution results. This innovation is called Adaptive Query Processing and consist of the three features: Adaptive Memory Grant Feedback; Interleaved Execution; Adaptive Joins.
SQL Server chooses parallel plans based on the costing (there are also some other factors that should be met for the plan that it can go parallel). Sometimes serial plan is slightly cheaper than a parallel, so it is assumed to be faster and picked by the optimizer, however, because the costing model is just […]
While preparing the post about Adaptive Joins, I’d like to share a quick post about the hidden gem in SQL Server 2017 CTP 2.0, discovered recently. In this short post, we will look at how you can determine what statistics are used by the optimizer during a plan compilation in SQL Server 2017. Prior to […]
Database administrators have a lot of tasks and responsibilities but perhaps the most challenging task is performance tuning. Because performance tuning issues can cause huge problems in the business area, database administrators have to monitor performance metrics and have to get immediate, if not sooner, notifications when the performance values cross an optimal state. Generally, […]
In this post, we are going to look at the new feature in SQL Server 2017 – interleaved execution. You need to install SQL Server 2017 CTP 1.3 to try it, if you are ready, let’s start. Now, when a CTP 2.0 of SQL Server 2017 is out, you don’t need to turn on the […]
Nowadays a lot of developers use Object-Relational Mapping (ORM) frameworks. ORM is a programming technique that maps data from an object-oriented to a relational format, i.e. it allows a developer to abstract from a relational database (SQL Server, for example), use object-oriented language (C#, for example) and let an ORM to do all the “talks” […]
One of the most important roles of a database administrator is to constantly protect the integrity of the databases and maintain the ability to recover quickly in case of a failure. In light of this, it’s critically important to have a backup-and-recovery strategy in place in order to be ready for an emergency. A key […]
In this post, I continue the exploration of SQL Server 2017 and we will look at the nonclustered columnstore index updates. Columnstore index has some internal structures to support updates. In 2014 it was a Delta Store – to accept newly inserted rows (when there will be enough rows in delta store, server compresses it […]
Some time ago, SQL Server 2017 was released and issued as CTP. The most exciting release in that CTP was that SQL Server now supports Linux! This is awesome and I consider it to be great news for many people. I am personally interested in the new features of query processing, and finally I had […]
In this post we continue looking at the Cardinality Estimator (CE). The article explores some join estimation algorithms in the details, however this is not a comprehensive join estimation analysis, the goal of this article is to give a reader a flavor of join estimation in SQL Server. The complexity of the CE process is […]
Yesterday I came across a question on one of SQL forums, that I may rephrase like: “Does a query plan compilation depend on how busy SQL Server is”. Before we go further, I should explicitly mention that we talk about a Compiled plan, not an Executable plan. Plan execution will of course depend on how […]
SQL Server backups, in itself, is a vast subject; so vast, there are multiple books written about them. In this article, however, we are going to focus on the types of backups that are available to us, and understand how to pick what we need, and what aspects we base that decision on. This understanding […]
A recovery model is a database configuration option that determines the type of backup that one could perform, and provides the ability to restore the data or recover it from a failure. The recovery model decides how the transaction log of a database should be maintained and protects the data changes in a specific sequence, […]
This is a note about multi-statement table valued functions (MTVF) and how their cardinality is estimated in the new CE framework. In the old CE framework the MTVF had fixed estimate of one row, in the new one the estimate is still fixed, however, now it is 100 rows. That’s the whole story. =)
In this blog post, I’m going to look at the place of the Cardinality Estimation Process in the whole Optimization Process. We’ll see some internals, that will show us, why the Query Optimizer is so sensitive to the cardinality estimation. To understand that we should observe the main steps that a server performs when the […]
This post opens a series of blog posts dedicated to my observations of the new cardinality estimator in SQL Server 2014. But, before we jump to the new features, I’d like to provide some background, to make the next posts clearer. We’ll start by discussing the role of Cardinality Estimation in SQL Server, trying to […]
This is the second article in the “Backup and Restore (or Recovery) in SQL Server” stairway series (see the full TOC below). This article deals with the different phases of data management life cycle and it encompasses the following topics: Introduction to data corruption Defining data corruption and its causes Discussion on the impact of […]
There has been an ever-growing discomfort on documenting things especially when it’s very dynamic in nature and I was at one time undergoing the same. We have been developing SQL Server Analysis Tabular Model’s, which were quite a many in numbers and documenting 50 or 60 models manually is a big effort. In addition, development […]
In a manner of speaking, planning and implementing a SQL Server backup design is an art. Backup, Restoration, Recovery, Business Continuity Plans (BCP), and Disaster Recovery (DR) are different phases of data revolving around the discussions involving data backup. In other words, it’s about how we ensure to retain the business data through any sort […]
The whole premise of Analysis Services (SSAS) is to place business logic into a central repository (a database). This central repository should be easy to understand from the average reporting user. Simplicity for SSAS databases starts with the Dimension and Fact tables in a data mart or data warehouse. These tables need to have as […]
SQL Server table hints are a special type of explicit command that is used to override the default behavior of the SQL Server query optimizer during the T-SQL query execution This is accomplished by enforcing a specific locking method, a specific index or query processing operation, such index seek or table scan, to be used […]
Introduction This article will explain the main features in SQL Server 2017, 2016, 2015, 2014, 2012, 2008, 2005, 2000, 7, 6.5, 6.0, 4.2, 1.1 and 1.0. In the past, the first SQL Server versions supported OS/2 (an operative system created by Microsoft and IBM) and Windows. Now, the new versions of SQL Server (vNext and […]
Microsoft recently released a new and interactive command-line query tool for SQL Server with modern features such as auto-completion and syntax highlighting. It’s called mssql-cli and this fully open source tool works on cross-platform under the BSD-3 license.
Some of my previous articles on Python provided insight of the basics and the usage of Python in SQL Server 2017. Why would a SQL Server DBA be interested in Python An overview of Python vs PowerShell for SQL Server Database Administration Data Interpolation and Transformation using Python in SQL Server 2017 This article is […]
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