An important query is suddenly slow. Is it because statistics are out of date? This is tricky to figure out, and updating statistics right away can make troubleshooting even harder. Learn how to use query execution plans to get to the heart of the question and find out if stats are really your problem, or if it's something else. In this 35 minute episode:
00:39 SQL Server 2017 Announced
01:10 New video from Microsoft's Joe Sack demonstrating Adaptive Query Processing
03:05 This week's question: Are bad stats making my query slow?
05:26 Demo of finding plan in cache and analyzing stats begins
28:17 What to do when stats ARE the problem
Code samples: https://gist.github.com/LitKnd/f07848d59cedc61fd057d12ab966f703
Links from the episode:
SQL Server 2017 Adaptive Query Processing video by Joe Sack: https://www.youtube.com/watch?v=szTmo6rTUjM&feature=youtu.be
Michael J Swart on finding Dark Matter Queries: http://michaeljswart.com/2017/04/finding-your-dark-queries/
Got a question for Dear SQL DBA? https://SQLWorkbooks.com/ask
They made their index maintenance job smarter, and their queries got slower in production afterward. Could the index maintenance have harmed performance? In this episode...
00:50 Thinking about plan freezing in Query Store and multi-team process
03:15 This week's question about index maintenance and query performance
The dev server got bogged down during a deployment and lock timeouts were everywhere. Was the perfmon counter way off about how much memory was being used just for locks? In this episode...
00:33 What's new @ SQL Workbooks: Down the Rabbit Hole
03:00 This week's question about lock timeouts & memory in SQL Server
A database transaction log is expanding, even though the DBA is running log backups and doesn't see an open transaction? What's going on with this Availability Group?
Timestamps in this episode if you want to skip ahead:
00:49 What's new @ SQL Workbooks
03:22 Info on SQLPASS Summit Content Survey & a heads-up for aspiring precon speakers
05:35 This week's question about t-log growth
A few episodes ago, I talked about how learning about Write Ahead Logging was a light bulb moment for me, and helped me learn tons of concepts about backups and recovery. This week, we talk about when SQL Server turns things upside down and doesn't use write ahead logging: and what it has to do for recovery in these special cases.
When you migrate a database, it can be useful to prove that you moved all the data and didn't miss any transactions. Learn how to use a tail log backup in a migration scenario.
Learn what a Stack Dump is in SQL Server. Hear what happens when Kendra causes a stack dump against a test SQL Server instance under load. Learn how to find information about stack dumps on your SQL Server, and how to escalate them when required.
When you're a Junior DBA, it's really hard to take in all the information out there. Learn about write ahead logging: the concept that can help you make sense of recovery models and backup strategies in SQL Server. Kendra tells the story of the "Wow!" moment when she learned about write ahead logging from Kimberly Tripp of SQLSkills.com, and explains how this all works in SQL Server.
Will cloud services render DBAs obsolete? Does the cloud mean that developers will use less of SQL Server? Kendra talks about the future of database administration and gives tips on strategizing your career.
Learn why the output from the built-in procedure sp_who2 can be so confusing, how to get more information, and free tools that can make it easier to figure out what you need to pay attention to in SQL Server.
Learn where full-text search shines, a common problem which full-text search does NOT solve, where full-text can run into performance problems.
Learn the difference between heaps, clustered and nonclustered indexes, primary keys, and columnstore indexes in SQL Server.
Learn how to approach the unexpected in a mysterious execution plan that contains way more operators than expected for a very simple SQL Server query.
Performing a switcharoo between new and old tables can cause blocking nightmares. Partition switching may help, surprisingly even on non-partitioned tables.
You need to release schema changes while the SQL Server is in use. Learn why code generation tools write odd scripts and how to stay sane amid rapid releases.
Does your team know what it's doing with SQL Server? Learn what a consultant looks for when assessing a team, and signs that SQL Server may be badly configured.
The first time you test a query it's slow, but when you run it again, it's much faster. Learn how SQL Server uses memory to make the second run much faster.
Learn why SQL Server 2016 SP1 is a game changer, and how to take best advantage of all the cool features now in Standard and Web Editions.
Learn about new features to speed up SQL Server queries. Kendra talks about automatic index tuning and speculates about Adaptive Query Processing.
As a database administrator or developer, you'll get into trouble fast if you try to force all your code and processes into a database shaped hole. You have to be creative when you problem solve -- and when you communicate! So how do you cultivate creativity?
The bigger your indexes are, the harder your index maintenance falls. Is it better to rebuild big indexes? Or should you reorganize? Learn the pros and cons of each command and other options.
Should you look at automatically created statistics on your tables in SQL Server to help you design better indexes?
What tools in SQL Server will notify you about blocking and help track the queries behind your toughest blocking and deadlocking problems?
Should you always index your foreign keys? What if you index them, and then the index never gets used?