Altering an Indexed Text Column

In this post, I am going to demonstrate how increasing the size of a text column with an index on it can lead to serious troubles without warning. I tested it two instances of SQL Server: SQL Server 2016 and 2017, but the same behavior should be expected with older versions; only the maximal allowed […]

SQL PASS Austria Meeting April: SQL Server Extended Events & Simple Rules for Clear and Attractive Visuals

Im kommenden SQL Server Community Meeting am Mittwoch, 15. April 2015 geht es um SQL Server Extended Events und Daten Visualisierung. Ich freue mich sehr, dass diesmal das Meeting in meiner Firma bwin stattfindet. Wir werden um 17:30 starten, die Adresse lautet: Marxergasse 1B, 1030 Wien.   Making the Leap from Profiler to Extended Events If you’re […]

Beyond Statistics Histogram Part 4 – Significant Performance Regression in SQL Server 2014

In the previous articles we’ve covered differences in estimations between the old and new CE related to queries that use predicates with literals which values are beyond the statistics histogram. We saw some issues with key ascending columns in SQL Server 2012 which can be solved with the trace flags 2389, 2390 and 4139. And […]

Speaking in Lisbon at SQLSaturday Portugal

I’ am really excited to back as a speaker to my favorite SQL Saturday event – Sql Saturday Portugal in Lisbon. The SqlSat 369 will be my fourth event in one of the most beautiful cities in the world. I am happy to see all my Portuguese friends feat. world wide freinds from Sqlfamily. My […]

SQL Server Konferenz 2015 – Slide Decks and Sample Code

I had a great time in Darmstadt, on  the largest SQL Server conference in the German speaking area “SQL Konferenz 2015“. I was very happy to see a lot of people in the room for my session SQL Server 2014 and Ascending Key Problem in Large Tables and want to thank all the attendees. It […]

Beyond Statistics Histogram – Part 3 (TF 2389 feat. TF 4139)

In the previous article we’ve shown how can we use TF 2390 to handle queries with literals beyond statistics histogram in SQL Server 2012. We saw that SQL Server creates some statistics on the fly for all columns used in filter expressions. If we would enable trace flag on the instance level that means that […]

Speaking at Deutsche SQL Server Konferenz 2015 in Darmstadt

I am honored  to have been selected to speak at the largest SQL Server conference in the German speaking area “SQL Konferenz 2015“. The 2-day conference will be held from 4 to 5 February 2015, with a pre-con day on 3rd February. I’ll be presenting a session about Key Ascending problems with large tables in […]

Beyond Statistics Histogram – Part 2 (TF 2390)

In the previous article of this series we introduced the problem with queries using literals which are beyond statistics histogram, but exist in the table. We saw that this can be a serious problem in large tables in SQL Server 2012. We saw also that SQL Server 2014 handles it better. In this article we’ll […]

Beyond Statistics Histogram – Part 1

In this article I will start to examine estimations and execution plans for queries that compare values in columns with literal values which are beyond the statistics histogram for that column. The problem is also known as key ascending column statistics problem. As in previous posts we remain here conservative regarding sample tables. We’ll create […]

A Funny Bug with New CE or Introduction to Out-of-Histogram Estimations

Since the release of SQL Server 2014 you can find several articles and blog posts about the changes in the new redesigned cardinality estimator. An excellent and detailed guide about the changes in the new CE you can find in the white paper Optimizing Your Query Plans with the SQL Server 2014 Cardinality Estimator. Almost […]