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Day: January 23, 2017

Finding Abnormally Long-Running Jobs

Published 2017-01-23 by Kevin Feasel

Lori Brown has a script to find jobs running longer than their 30-day average:

I needed to update some of our long running job monitoring code to improve it from the version that we have right now. I like this version because it uses msdb.dbo.syssessions (https://msdn.microsoft.com/en-us/library/ms175016.aspx) to validate that a job is actually running. I also wanted to know the percent difference between the current run duration versus an average duration per job from the past 30 days. I decided to place the calculated average into a table variable and then join on it to get my results. I also used the IIF function (https://msdn.microsoft.com/en-us/library/hh213574.aspx) to help me avoid a divide by zero error that comes up when the average duration equals 0.

One thing which could cut down on false positives would be to calculate the standard deviation as well.  I wouldn’t automatically assume that job executions were normally distributed, but if you look at things more than one standard deviation away from the mean, it should remove noise of jobs which are just a little over the average but not in dangerous territory.

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Graphs In SQL

Published 2017-01-23 by Kevin Feasel

Joe Celko models graphs using ANSI SQL:

The initial proposed solutions to construct the subgraphs were essentially procedural traversal, dumping pairs of nodes into a temp table and incrementing a counter.

Let us try getting out of a procedural mindset and starting to think in sets instead. Let us give each subgraph a name, and a member node. Essentially, this directly models. The diagram I just gave you a paragraph or two ago. The next question is how do we get names for the subgraphs. I will propose the simple solution that each subgraph takes the name of the lowest element in it. This would give us a table that looks like this:

Read the whole thing.  Given the recent revival of graph databases, it’s important to take note that you can model the network-style problems using either graphs or relations; the trick is figuring out which is going to give you better long-run performance.

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CTP 1.2 For vNext

Published 2017-01-23 by Kevin Feasel

The SQL Server team has announced that the latest CTP of vNext is available:

Key CTP 1.2 enhancement: Support for SUSE Linux Enterprise

In SQL Server v.Next, a key design principle has been to provide customers with choice about how to develop and deploy SQL Server applications: using technologies they love like Java, .NET, PHP, Python, R and Node.js, all on the platform of their choosing. Now in CTP 1.2, Microsoft is bringing the power of SQL Server to SUSE Linux Enterprise Server, providing more deployment options and a streamlined acquisition process.

That makes three mainline distributions supported:  Ubuntu, Red Hat, and now SuSE.

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Thinking About Dead Connections

Published 2017-01-23 by Kevin Feasel

Lonny Niederstadt has a half-baked idea on dead connections:

In SQL Server 2005, a valuable addition was made.  SQL Server would use a “Keep Alive” value specified specifically per instance, rather than the KeepAliveTime specified by the Windows registry.  It defaulted to 30000 ms/30 seconds.

The blog post below explains this new addition, and mentions that the interval for SQL Server will be a fixed 1000 ms/1 second, regardless of the KeepAliveInterval specified in the Windows registry. At the time SQL Server 2005 was introduced, TCPMaxDataRetransmissions from the Windows registries still controlled the maximum number of probes.

Read on for more.

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Streaming Data To Power BI

Published 2017-01-23 by Kevin Feasel

Sacha Tomey builds a quick Powershell script to feed streaming data into Power BI:

Peter showed off three mechanisms for streaming data to a real time dashboard:

  • The Power BI Rest API
  • Azure Stream Analytics
  • Streaming Datasets

We’ve done a fair bit at Adatis with the first two and whilst I was aware of the August 2016 feature, Streaming Datasets I’d never got round to looking at them in depth. Now, having seen them in action I wish I had – they are much quicker to set up than the other two options and require little to no development effort to get going – pretty good for demo scenarios or when you want to get something streaming pretty quickly at low cost.

Click through for more details and a sample script.

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CONCAT_WS()

Published 2017-01-23 by Kevin Feasel

Manoj Pandey points out a new string function in SQL Server vNext:

Here in this post I’ll discuss about one more new function i.e. CONCAT_WS(), here “_WS” means “With Separator”.

This is very similar to the existing CONCAT() function introduced back in SQL Server 2012, which concatenates a variable number of arguments or string values.

The difference is the new function CONCAT_WS() accepts a delimiter specified as the 1st argument, and thus there is no need to repeat the delimiter after very String value like in CONCAT() function.

It’s a small change, but I think a rather useful one.  Do think about how you’d want to interpret NULL values, though, as CONCAT_WS() does not include separators for NULL values.

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Cloned Database Size

Published 2017-01-23 by Kevin Feasel

Joey D’Antoni tests how large database files are after running DBCC CLONEDATABASE:

One of the recent feature introductions to SQL Server is dbcc clonedatabase, a feature that lets you create a “data-less” clone of you database. All of the statistics and objects come into your cloned database, however none of the data does. This is perfect for development or performance tuning exercises, where you want all the metadata, but do not want the security risk of dealing with production data.

Recently I had the opportunity to use clonedatabase on a very large database. I was concerned about the size of the data files and how this would impact space on my volumes. Books Online is fairly clear, but I wanted to see for myself.

Click through for the answer.

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NCCI Online Rebuild

Published 2017-01-23 by Kevin Feasel

Niko Neugebauer notes a big improvement in vNext:

For the Columnstore Indexes, the only online operation for the indexes that was available so far, was the Row Group Merging and Removal with ALTER INDEX REORGANIZE (as well as the Tuple Mover operations). With appearance of HTAP scenarios (Hybrid Transactional Analytical Processing aka Operational Analytics) in SQL Server 2016, there was a huge need for the online index maintenance, making sure that the operational part of the HTAP runs smoothly. For any online business, taking their application down for an hour means loosing real money and even worse – loosing credibility from their customers. To my knowledge, Microsoft was very much aware and was working on improving this missing part.
For the SQL Server vNext version (after SQL Server 2016) in CTP 1.2, yesterday, we have finally received the first Online Rebuild operation for the Columnstore Indexes – in this case for the Nonclustered Columnstore Indexes, and this is a huge news for anyone using the HTAP scenarios.
Naturally this feature is Enterprise Edition Only, and like ever before – if you are running a critical workload, you need to step up and use the Enterprise Edition.

Online clustered columnstore reorganization in 2016 was a life-saver, and I’m looking forward to online clustered columnstore rebuilding at some point in the future.

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