Pinal Dave Helps Me Fix My Performance Tuning Problems

Published on: 2018-07-24

Be sure to check out this week’s video on YouTube.

This week I was fortunate enough to film a video in collaboration with Pinal Dave, the SQL Authority himself.  Pinal is creative, hilarious, and kind; making this video with him was A BLAST!

Although the video is a little tongue in cheek, Pinal’s recommendations are very real: I’ve encountered plenty of scenarios where these solutions fixed slow queries.  Will these recommendations fix the problem in every situation?  Of course not, but they are a great place to start.

Instead of creating a text version of the concepts covered in the video (you should really watch it), I thought it would be fun to do a behind-the-scenes narrative of how the video came together because it is unlike any other project I’ve done before.

The Idea

After agreeing to make a video together, we tossed around a few ideas.  Because we live in different time zones, we thought it would be a fun to do something where I kept waking Pinal up in the middle of the night.

We iterated over what SQL Server examples to use (originally the second example was going to show my queries running out of space because autogrowth being turned off).  We also ended up adding another example after my wife suggested that having it build to three scenarios instead of two would be funnier – I agree!

Asynchronous Filming

You’ve probably already figured it out, but I didn’t really wake Pinal up in the video (honestly, I think midnight would be too early to wake him up anyway; in our back and forth emails, I was seeing responses from him that were in the 1-2am range).

I filmed a preliminary version of my parts of the video, very roughly edited them together, and sent it over to Pinal.

He then filmed his segments, giving me lots of great footage (I’m not sure if it was ad-libbed or not, but I was dying of laughter when watching through his clips).

Then I re-filmed my parts to try to match his dialog as closely as possible.  Re-filming my parts also allowed me to self-edit and not ramble as much.

Everything Else

After that, it was just the usual process of editing, color correction, audio processing, etc…

I’m happy with how it turned out, especially given all of the technical challenges we had with filming separately.

Major thanks again to Pinal for being supportive and willing to make a fun SQL Server video.  Enjoy!

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How To Make Your Queries Perform Like They Used To

Published on: 2017-09-19

Photo by Chad Kirchoff on Unsplash

Prefer watching on YouTube

In the ideal world, you fully test how your SQL Server will handle upgrading to the latest version.  You’re able to catch and mitigate any performance surprises early on.

In the real world, you might not be able to perform a good test before upgrading.  You only learn about poor performance once you upgrade in production.

Does this scenario sound familiar?  It’s what I’ve been thinking about recently as I have to deal with query performance issues after upgrading to SQL Server 2016.

Coming from SQL Server 2012, I know the new cardnality estimator added in 2014 is a major source of the problems I’m experiencing.  While the new cardinality estimator improves performance of some queries, it has also made made some of my queries take hours to run instead of seconds.

Long-term, the solution is to revisit these queries, their stats, and the execution plans being generated for them to see what can be rewritten for better performance.

But ain’t nobody got time for that (at least when facing performance crippling production issues).

Short-term, put a band-aid on to stop the bleeding.

I could change the compatibility mode of the database to revert back to SQL Server 2012 (before the new cardinality estimator was introduced), but then I miss out on being able to use all of the new SQL Server 2016 improvements just because a few queries are misbehaving.

I could enable trace flag 9481 to have my queries use the old cardinality estimator, however as a developer I probably don’t have access to play with trace flags (and for good reason).

Starting with 2016 SP1, what I can do is use the legacy cardinality estimator query hint:

This hint is great because it doesn’t require developers to have any special permissions.  It also allows SQL to use the old cardinality estimator for poor performing queries only – the rest of the server gets to benefit from the improvements brought on by the new cardinality estimator.

With time, I can revisit the queries that are using this hint to try to improve their performance, but in the mean time it’s a great way to fix regressed query performance due to the new cardinality estimator.

Thanks for reading. You might also enjoy following me on Twitter.

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