Tuning Apache Solr

Michael Sun explains how to optimize Apache Solr’s memory usage:

For Oracle JDK 8, both CMS and G1 GC are supported. As rule of thumb, if the heap size is less than 28G, CMS works well. Otherwise G1 is a better choice. If you choose G1, there are more details about G1 configuration in the part 2 of this blog. You can also find helpful guidance in Oracle’s G1 tuning guide.

Meanwhile it’s always a good idea to enable GC logging. The overhead of GC logging is trivial but it gives us a better understanding how the JVM uses memory under the hood. This information is essential in GC troubleshooting. Here is an example of GC logging settings.

There’s some good administrative assistance, but also tips on more efficient querying.

Azure Private Virtual Networks

The Tech Junkie shows how to create a private virtual network in Azure:

In the previous blog post we created an Azure cloud service.  Now we are going to create a private virtual Azure network.  The importance of this is that when you create a virtual machine in Azure you will use this virtual network to connect to your virtual machine.

This is a screenshot-driven, step-by-step post that makes setting these up easy.

Dot-Density Maps In R

Paul Campbell shows how to build a dot density map in R:

To get me started I invested in the expert guidance of data-visualiser-extraordinaire Nathan Yau, aka Flowing Data. Nathan has a whole host of tutorials on how to make really great visualisations in R (including a brand new course focused on mapping) and thankfully one of them deals with how to plot dot density using base R.

Now with a better understanding of the task at hand, I needed to find the required ethnicity data and shapefiles. I recently saw a video of Amelia McNamara’s great talk at the OpenVis Conference titled ‘How spatial polygons shape our world’. The .shp file really is a glorious thing and it seems that the spatial polygon makers are the unsung heros of the datavis world, so a big round of applause for all those guys is in order.

Anyway, I digress. Luckily for me, the good folks over at the London DataStore have a vast array of Shapefiles that go from Borough level all the way down to Super Output Area level. I’m going to use the Output Areas as the boundaries for the dots and the much broader Borough boundaries for ploting area labels and borders.

The ethnic group data itself was sourced from the Nomis website which has a handy 2011 Census table finder tool where you can easily download an Ethnic Group csv file for London output areas. Vamonos.

I’m going to give this a second reading; it’s a great example of how to go from functional to beautiful.  H/T David Smith

Basic Parsing On Invoke-WebRequest

Andy Levy shows how to handle complex redirects with Invoke-WebRequest in Powershell:

So off to the PowerShell prompt I went and ran Invoke-WebRequest -Urihttp://firstresponderkit.org/ to start looking at the object returned so I could see what I needed to parse out to find my way to the true download URL.

Then Firefox (my default browser) opened, and I was staring at https://github.com/BrentOzarULTD/SQL-Server-First-Responder-Kit/tree/master.

I was expecting an HTTP 30X redirect status code which, based upon previous experience, Invoke-WebRequest would honor. Instead, I got a 200 OK which is the web server saying “yep, here’s your stuff, HAND!”

Read on for the solution.

Out Of User Memory Quota

Jack Li troubleshoots an In-Memory OLTP error:

[INFO] HkDatabaseTryAcquireUserMemory(): Database ID: [7]. Out of user memory quota: requested = 131200; available = 74641; quota = 34359738368; operation = 1.

This is my first time to see this error.  As usual, I relied on source code to find answers.   The message is a result of enforcing memory quota for In-memory OLTP usage.  As documented in “In-Memory OLTP in Standard and Express editions, with SQL Server 2016 SP1”, SQL Server 2016 SP1 started to allow In-Memory OLTP to be used in all editions but enforce memory quotas for editions other than Enterprise edition.  The above message is simply telling you that you have reached the quota and what ever operation you did was denied.

Jack provides more context around the error as well.

Finding Failed Queries

Andrew Pruski shows how to use extended events to find queries with errors:

What this is going to do is create an extended event that will automatically startup when the SQL instance starts and capture all errors recorded that have a severity level greater than 10.

Full documentation on severity levels can be found here but levels 1 through 10 are really just information and you don’t need to worry about them.

I’ve also added in some extra information in the ACTION section (for bits and bobs that aren’t automatically included) and have set the maximum number of files that can be generated to 10, each with a max size of 5MB.

Check it out.  At one point, I had created a small WPF application to show me errors that extended events caught.  It completely freaked out a developer when I IM’d him and told him how to fix the query he’d just run from the privacy of his cube, with me nowhere to be seen.

Creating Nicer Reports

Reid Havens has a few tips for making Power BI reports look nicer:

This is less of a single applied step as it is multiple formatting practices applied throughout the report. I’ve already hit on this subject a little bit in the two previous Power BI visual design practices in regards to using complimentary colors. The two key takeaways in this section are object formatting and color coordination.

Of all my best practices I’m showcasing here I’d say this one is the most subjective. However I think that maintaining complimentary colors goes a long ways to creating a professional looking report. I also have a strong dislike for the default title design for visualizations in Power BI. By default it is left aligned and a grey color (AGAIN…hard to read!). I center that sucker and color the background. An added benefit to coloring the title background is it actually forces me to make sure my objects are aligned, otherwise it is VERY noticeable now if they aren’t.

Definitely read the comments on this one, as some of these tips are subjective.

The REVERSE Function

John Morehouse explains what the REVERSE function is and why it can be useful:

Recently I had a conversation with a colleague that wasn’t aware of the REVERSE function in SQL Server.  I had sent them a code snippet and they inquired as to what the purpose of the function was.  Essentially, this function that reverses any string value.

For example, the phrase:

The brown dog jumped over the lazy fox

reversed looks like this

xof yzal eht revo depmuj god nworb ehT

Read on to see a good example of when you might use REVERSE.

Mapping File Shenanigans With The Import/Export Wizard

Angela Henry ran into problems copying a boatload of data from a mainframe-hosted DB2 server and has lived to tell the tale:

This post talks about the issue I ran into with SSIS Mapping Files.

We currently run DB2 on an IBM iSeries AS400 for our ERP system.  I was tasked with copying data from the AS400 to a SQL Server database for some consultants to use.  The C-Suite didn’t want to give the consultants access to our AS400, so this was the work around that was put forth and accepted (and no, no one asked me before I was “voluntold” for the task).  Since this would essentially be a “one-time” thing, I chose to use the Import Export Wizard, but I would save the package just in case they wanted this process repeated.

Sounds like it was a painful experience, but it does have a happy ending.

C Complier Errors With Memory-Optimized Objects

Arun Sirpal ran into an issue with memory-optimized tables:

Naturally (whether right or wrong) I thought that it could be corruption and I didn’t want to rule it out. I headed straight to the error log to see if it could guide me, all this did was confuse me. However after some research it led me to conclude that “Unable to call into the C compiler GetLastError = 2” for the specific error code shown below meant that a specific file(s) could not be found, I was thinking exactly what file(s)?

This is a snippet from the error log when the database went through recovery – Seems to even struggle during the analysis phase and the checkpoint failure was throwing me off slightly.

It’s worth reading in case you experience this error.

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