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Author: Kevin Feasel

Foreign Key Batch Drop And Re-Create

Published 2017-06-16 by Kevin Feasel

Louis Davidson has a utility to batch drop and re-create foreign key constraints:

I was working on a database a few weeks back (maybe longer, I am kind of busy with several projects right now), and I wanted to truncate a set of tables. There was one central table, and 8 tables related by a FOREIGN KEY constraint. The central table had 6 million rows, and a few of the other tables 20+ million. TRUNCATE is amazingly fast,and when I tried to just use DELETE, it took almost as long as it took me to load the tables. (Exaggeration? A little bit, but not as much as you might imagine, since I use SSIS to BULK LOAD these tables, and the source data is very simple.)

I could just get rid of the constraints, but as a relational db lover, I love constraints. When enforced, they protect me. When not enforced (like when SSIS disables them for a BULK LOAD operation), they are still good documentation. So as any good nerd programmer type would, I started coding a tool to deal with the constraints for me. And as a decent blogger, as soon as it started to get interesting, I realized I could blog about it and upload the code to my website. This in the end makes the code better, because I have to test more, and I learn stuff from readers reminding me things (like a FK script needs to honor CASCADE and NOT FOR REPLICATION, oops.)

Read on for a link to the utility, as well as an example.

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The Costs Of Statistics Updates With FULLSCAN

Published 2017-06-16 by Kevin Feasel

Kendra Little explains what happens when you update a table’s statistics with FULLSCAN:

On my test instance, the command that uses the default sampling takes 6 seconds to complete.

The command which adds “WITH FULLSCAN” takes just over five minutes to complete.

The reason is that those two little words can add a whole lot of extra IO to the work of updating statistics.

Kendra shows the query plans for each statistics update in some detail.  It’s a very interesting post, well worth taking the time to read.

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DevOps T-SQL Tuesday Roundup

Published 2017-06-16 by Kevin Feasel

Grant Fritchey puts a bow on the latest T-SQL Tuesday:

Thank you to everyone who participated in T-SQL Tuesday #091 which was on databases and DevOps. As I anticipated, this brought out quite a bit of variety on the posts. This is because DevOps is still… not quite cooked…(?) in many peoples minds. I think with the range of posts we saw here, it’ll be a lot more clear to those who are just getting an introduction to it. Here are the posts (in no particular order) and a few comments on each:

Click through to see all the entrants.

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New Version Of dplyr

Published 2017-06-15 by Kevin Feasel

Hadley Wickham reports that dplyr is now at version 0.7.0:

dplyr 0.7.0 is a major release including over 100 improvements and bug fixes, as described in the release notes. In this blog post, I want to discuss one big change and a handful of smaller updates. This version of dplyr also saw a major revamp of database connections. That’s a big topic, so it’ll get its own blog post next week.

Read on to learn about tidy evaluation and the Star Wars data set.  There’s a lot to wrap your head around in this release.

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Power BI Report Server Released

Published 2017-06-15 by Kevin Feasel

Ginger Grant notes that Power BI Report Server is now generally available:

The most glaring change from what was announced earlier, is Power BI Report Server can only connect to analysis services data sources, both tabular and multidimensional.  If you want to connect to SQL Server, Oracle or Excel or all three, use the Power BI Web Service.  Only going to the cloud version will users be able to create a data mashup or connect to anything but SQL Server.

Connecting to one data source is not what was promised when the Power BI Report Server was announced in May.  Various Power BI Product members held a session at the Microsoft Data Summit where attendees were able to ask questions.  I asked “When are we going to be able to use Power BI Report Server with data sources other than analysis services?”  In a room full of people, I was assured that it was a top priority of the team to release the same data connectivity functionality for Power BI Report Server that currently exists for Power BI Services and the current plan was to release this functionality the next release.

This is the most glaring flaw with Power BI Report Server at the moment.  Unfortunately, that probably makes it DOA for my purposes, at least until they introduce SQL Server relational as a valid data source.

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Planning A Power BI Enterprise Deployment

Published 2017-06-15 by Kevin Feasel

Melissa Coates announces a new whitepaper co-authored with Chris Webb:

I’m excited to share that a new technical whitepaper I co-authored with Chris Webb is published. It’s called Planning a Power BI Enterprise Deployment. It was really a fun experience to write something a bit more formal than blog posts. My interest in Power BI lies in how to successfully deploy it, manage it, and what the end-to-end story is especially from the perspective of integration with other data assets in an organization. Power BI has grown to be a huge, wide set of features so we got a little verbose at just over 100 pages.

It is a beefy whitepaper.  I haven’t had a chance to read it yet, but it’s now on my list.

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Using rxInstallPackages

Published 2017-06-15 by Kevin Feasel

Tomaz Kastrun explains how to use rxInstallPackages to install packages on Microsoft R Server:

In rxInstallPackages function use computeContext parameter to set either to “Local” or to your  “SqlServer” environment, you can also use scope as shared or private (difference is, if you install package as shared it can be used by different users across different databases, respectively for private). You can also specify owner if you are running this command out of db_owner role.

This updated installation method is certainly easier than the prior method, which included incantations and sacrificing a chicken.

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The Downside Of Oversizing

Published 2017-06-15 by Kevin Feasel

Aaron Bertrand shows why you might not want to oversize VARCHAR columns by too much:

Now, whether you go by the old standard or the new one, you do have to support the possibility that someone will use all the characters allowed. Which means you have to use 254 or 320 characters. But what I’ve seen people do is not bother researching the standard at all, and just assume that they need to support 1,000 characters, 4,000 characters, or even beyond.

So let’s take a look at what happens when we have tables with an e-mail address column of varying size, but storing the exact same data:

This is a good argument against automatically using VARCHAR(8000) (much less MAX) when creating columns.

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Checking Backup Encryption Size Differences

Published 2017-06-15 by Kevin Feasel

Tracy Boggiano has a script to check whether your backup file sizes are larger or smaller when they’re encrypted:

I had a recent project to enable backup encryption on all our servers.  Then question from the storage team came up will this required additional space.  Well by then I had already enabled in all our test servers so I wrote a query that would compare the average size of backups before encryption to after encryption.  Keep in mind we do keep only two weeks of history in our backup tables so this is a fair comparison.  If you don’t have maintenance tasks to clean up your backup history then you should have backup_start_time to the where clauses to get more accurate numbers and setup a maintenance tasks to keep your msdb backup history in check.

Unfortunately, Tracy leaves us in suspense regarding whether they did increase.

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Duplicate Key Error On DBCC CLONEDATABASE

Published 2017-06-15 by Kevin Feasel

Erin Stellato shows an edge case when you have a rather old database you’re trying to clone:

If you’ve been using DBCC CLONEDATABASE at all, you might have run into a cannot insert duplicate key error (or something similar) when trying to clone a database:

Database cloning for ‘YourDatabase’ has started with target as ‘COPY_YourDatabase’.
Msg 2601, Level 14, State 1, Line 1
Cannot insert duplicate key row in object ‘sys.sysschobjs’ with unique index ‘clst’. The duplicate key value is (1977058079).

If you do some searching, you’ll probably end up at this Connect item: DBCC DATABASECLONE fails on sys.sysowners.

The Connect item states that the problem exists because of user objects in model.  That’s not the case here.

I’m working with a database created in SQL Server 2000…now running on SQL Server 2016.

This isn’t very likely to pop up for most places (I hope!), but it’s good to know.

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