A Fine Slice Of SQL Server
Erik Darling hosts a showdown:
I often speak with people who are confused about what these settings do, and which one they should be using to fix certain problems.
The first myth is that Optimize For Ad Hoc Workloads has some special effect on queries run outside of stored procedures: it does not. It’s very poorly named in that regard. There are no special optimizations applied because of that setting.
Read the whole thing.
Comments closedCathrine Wilhelmsen shares a tip for improving those presentation skills:
Did you know that PowerPoint can help you improve your presentation skills? 💡 If you rehearse with the PowerPoint Presenter Coach, you can get real-time feedback on things like your pace and language. If that’s too distracting (it is for me), you can choose to hide the real-time feedback and only view the detailed report at the end of your rehearsal.
The report shows you details about the total time spent, your pace and pitch over time, whether or not you are simply reading from your slides, as well as actionable feedback on your language. The feedback includes whether you are using too many filler words (like umm, actually, or you know), whether you are using too many repetitive words with alternatives you can use instead, whether you are using any words that can be offensive, and specific sentences that you can refine.
Click through for more details.
Comments closedThe Hadoop in Real World team explains what accumulators are in Spark:
Accumulators are like global variables in Spark application. In the real world, accumulators are used as counters and keep to keep track of something at an application level. Accumulators serve a very similar purpose as counters in MapReduce.
Read on for examples, as well as a warning against using them in a map() operation.
Paul Randal wraps up a series on latches with a few miscellaneous entries:
When either a heap or an index is being accessed, internally there’s an object called a HeapDataSetSession or IndexDataSetSession, respectively. When a parallel scan is being performed, the threads doing the actual work of the scan each have a “child” dataset (another instance of the two objects I just described), and the main dataset, which is really controlling the scan, is called the “parent.”
When one of the scan worker threads has exhausted the set of rows it’s supposed to scan, it needs to get a new range by accessing the parent dataset, which means acquiring the ACCESS_METHODS_DATASET_PARENT latch in exclusive mode. While this can seem like a bottleneck, it’s not really, and there’s nothing you can do to stop the threads performing a parallel scan from occasionally showing a LATCH_EX wait for this latch.
Click through to read the whole thing.
Comments closedChris Webb has a public service announcement:
When you tune a Power BI report or dataset refresh your first job is to make it run faster – users hate slow reports and late data. However, if you are using Power BI Premium you also need to think about reducing the amount of CPU used by a query or refresh as well, and in this post I’ll explain why.
Click through for that explanation.
Comments closedLee Markup takes us through a pair of very useful functions in SQL Server:
SQL Server concatenation methods have been enhanced in modern versions of SQL Server. SQL Server 2012 introduced the CONCAT() function. In SQL Server 2017 we get CONCAT_WS().
A common usage of concatenation, or joining column values together in a string, is combining a FirstName and LastName column into a FullName column. Another common usage might be for creating an address column that pulls together building number, street, city and zip code.
Read on to learn more. CONCAT() and CONCAT_WS() are also extremely helpful for change detection in ETL processes. For example, you might have a queue table to process and only want to update records in which relevant source fields changed, ignoring the ones which don’t exist in your destination. A combination of HASHBYTES() and CONCAT_WS() will do the trick quite nicely.
I recently blogged about punching developers in the brain when a software deliverable deadline is slipping. The title of the post is The Question Unasked. In this post, I would like to address software development estimation.
In the past, I have stated “Either all software developers are pathological liars or software development is inherently inestimable.”
Read on for Andy’s take. For mine, the overly short version is that incentives are set up for software estimation to fail due to perverse incentives and a lack of requirements. Ask the question, “How long will it take to build a skyscraper?” and you might get some answer, but it certainly won’t be the answer to the pertinent question, “How long will it take to build this skyscraper?” That’s because we haven’t talked at all about location, building plans, blueprints, regulatory requirements, financing, or any of the hundreds of other things which organizations talk about and do before they start slapping mortar on bricks. With software development, we’re expected to wing it and solve all of those sorts of problems along the way. Making it even better, more often than not, the skyscraper “pivots” to being a suspension bridge.
Comments closedChad Callihan explains why we need tail log backups:
When you are migrating a database from one server to another, how can you be sure to backup all transactions? Sure, you can notify the client and let them know “there will be a short outage at 8AM so please stay out of the application at that time.” Can you really trust that? Of course not. Let’s demonstrate the steps needed to include all transactions with the tail-log backup.
Protip: if you build your application such that nobody wants to use it, you can migrate the database much more easily. Assuming you don’t want to follow that outstanding advice, Chad has you covered.
Comments closedShivani Sarthi explains the value of Kafka Connect:
Kafka connect is not just a free, open source component of Apache Kafka. But it also works as a centralised data hub for simple data integration between databases, key-value stores etc. The fundamental components include-
– Connectors
– Tasks
– Workers
– Converters
– Transforms
– Dead letter Queue
Moreover it is a framework to stream data in and out of Apache Kafka. In addition, the confluent platform comes with many built-in connectors,used for streaming data to and from different data sources.
Click through for information on each component.
Comments closedTomaz Kastrun reminds me of xclock:
It is all about measuring time using useless clocks. Script takes a system time and displays any given clock in a rather “static” way. You can choose between analog, small digital and big digital clock. And when playing with the time, you can also learn something new.
Click through to see how to make an analog clock plot in R, and then try it again with a digital clock.
Comments closed