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Curated SQL Posts

Rolling Windows Upgrades with AGs + WSFC

Published 2019-09-03 by Kevin Feasel

Allan Hirt shows how you can combine Availability Groups with Windows Server Failover Clusters and upgrade the operating system version while keeping your SQL Servers running:

The configuration for a cluster rolling upgrade allows for mixed Windows Server versions to coexist in the same WSFC. This is NOT a deployment method. It is an upgrade method. DO NOT use this for normal use. Unfortunately, Microsoft did not put a time limit on how long you can run in this condition, so you could be stupid and do something like have a mixed Windows Server 2012 R2/2016 WSFC. Fire, ready, aim. The WSFC knows about this and you’ll see a warning with an Event ID of 1548.

Read on for a summary of what Allan has learned in doing this.

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Comparing CAST and CONVERT Performance

Published 2019-09-03 by Kevin Feasel

Max Vernon runs a performance test of CAST versus CONVERT:

This post is a follow-up to my prior post inspecting the performance of PARSE vs CAST & CONVERT, where we see that PARSE is an order of magnitude slower than CONVERT. In this post, we’ll check if there is a similar difference between using CAST or CONVERT. But just to be clear, CONVERT offers a lot more functionality than CAST; this post will not help you decide which of these functions to use for a specific use-case – I leave that to the reader to decide for themselves.

Max gets slightly different numbers but under the covers they both call the same CONVERT() function. The difference in numbers is noise: both of them have standard deviations of ~200ms, so a t-test can’t distinguish the two. The big choice is whether you’d rather have ANSI standard code (if so, use CAST()) or if you’d prefer additional functionality around dates and times (like CONVERT() offers).

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Migrating to SQL Managed Instances with dbatools

Published 2019-09-03 by Kevin Feasel

Jovan Popovic shows how we can perform an offline migration from on-prem/IaaS SQL Server to a SQL Managed Instance using dbatools:

Typically, the offline migration process looks like:

– You need to create an Azure Blob Storage account that will be used to temporary hold the database backups that will be moved from SQL Server to Managed Instance.
– You need to back up the databases to Azure Blob Storage and restore them from Azure Blob Storage to Managed Instance.
– You need to migrate server-level objects such as logins, agent jobs from the source to destination instance.

In this article, I will use Azure PowerShell to create and manage necessary Azure resources, and DBATools PowerShell library to initiate migration.

Read on for the process, including the Powershell scripts and dbatools calls needed.

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Verifying Database Backups

Published 2019-09-03 by Kevin Feasel

Lori Brown reminds us to perform checksums and verify backups on completion:

I found out that I have been missing something from our regular database backups that I had no idea that I should have been using all along.  I know about verifying your backup file and have incorporated into our standard maintenance routines one that will periodically test backups by restoring using VERIFYONLY.  However, I totally missed also having CHECKSUM specified when creating backup files.  Ugh!!  Not sure how that happened but I am totally onboard with it now.  Better late than never!

Lori does explain what the consequences are in terms of time and CPU utilization so that you’re aware of the tradeoffs when enabling these options.

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Breaking Out Powershell Functions with Powershell

Published 2019-09-03 by Kevin Feasel

Shane O’Neill shows us how we can use Powershell to break Powershell functions out into their own files:

The stupid thing that I was doing was that I was manually, visually scanning the script, copying out the function definitions, and pasting them into their own function files.

This was long, this was tedious, and this was not a efficient use of my time.

Especially since the scripts were not laid out as logically as I would have liked.

Click through to see how Shane solved this.

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Real-Time Analytics with Divolte, Kafka, Druid, and Superset

Published 2019-08-30 by Kevin Feasel

Fokko Driesprong gives us a proof of concept architecture for real-time analytics in the Hadoop ecosystem:

Divolte Collector is a scalable and performant application for collecting clickstream data and publishing it to a sink, such as Kafka, HDFS or S3. Divolte has been developed by GoDataDriven and made available to the public under the Apache 2.0 open source license.

Divolte can be used as the foundation to build anything from basic web analytics dashboarding to real-time recommender engines or banner optimization systems. By using a JavaScript tag in the browser of the customers, it gathers data about their behaviour on the website or application. You’re in full control what you do, and don’t want to capture.

Click through for the example.

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Combining Neo4j with Kafka

Published 2019-08-30 by Kevin Feasel

David Allen shows how you can use Neo4j to visualize graphic data living in Kafka:

We’re enabling the plugin to work as both a source and a sink. In the NEO4J_streams_sink_topic_cypher_friends item, we’re writing a Cypher query. In this query, we’re MERGE-ing two Person nodes. The plugin gives us a variable named event, which we can use to pull out the properties we need. When we MERGE nodes, it creates them only if they do not already exist. Finally, it creates a relationship between the two nodes (p1) and (p2).

This sink configuration is how we’ll turn a stream of records from Kafka into an ever-growing and changing graph. The rest of the configuration handles our connection to a Confluent Cloud instance, where all of our event streaming will be managed for us. If you’re trying this out for yourself, make sure to replace KAFKA_BOOTSTRAP_SERVERS, API_SECRET, and API_KEY with the values that Confluent Cloud gives you when you generate an API access key.

Click through for the example.

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SQL Server 2019 RC 1.1

Published 2019-08-30 by Kevin Feasel

Amit Banerjee announces a minor numeric change and a big update to SQL Server 2019 RC1:

In continuation with our announcement of SQL Server 2019 release candidate last week, we’re announcing that the release candidate refresh for SQL Server 2019 is now available to download. The release candidate now includes bits for Big Data Clusters in SQL Server 2019 in this refresh.

Back in July, we announced the preview of Big Data Clusters in SQL Server 2019 and since then we’ve seen our customers actively bringing their big data analytical workloads to SQL Server 2019 to operationalize their AI and machine learning projects.

Read on for more.

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SQL Injection without Dynamic SQL

Published 2019-08-30 by Kevin Feasel

Erik Darling has a card trick for us:

I always try to impart on people that SQL injection isn’t necessarily about vandalizing or trashing data in some way.

Often it’s about getting data. One great way to figure out how difficult it might be to get that data is to figure out who you’re logged in as.

There’s a somewhat easy way to figure out if you’re logged in as sa.

Wanna see it?

Of course you do.

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