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Author: Kevin Feasel

MySQL Security

Published 2022-05-20 by Kevin Feasel

Lukas Vileikis starts a series on security in MySQL:

Security is a critical part of any infrastructure – it’s even more so in the database world, where one step in the wrong direction can be the cause of system disruptions and downtime, customer dissatisfaction, and in the worst-case scenario – deaths.

As MySQL is one of the primary relational database management systems being used in the world today, it’s critical to understand how to go about properly the database infrastructure to keep data breaches away from the organization’s websites or, if they’ve happened already, to become a thing of the past.

The first article covers some of the basics of security in MySQL. The second promises to have more.

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An Index for Change Tracking Cleanup

Published 2022-05-20 by Kevin Feasel

James Ferebee creates an index:

If the issue persists and we stack a lot of data that needs to be removed which can be too much for autocleanup to manage. At that point, we recommend running (as is indicated in the error message) sp_flush_CT_internal_table_on_demand which is discusseed in detailed in Amit’s blog post Change Tracking Cleanup–Part 1.

I will not discuss the internals of the process as Amit Banerjee already touched on this in the referenced blog. However if you are routinely encountering issues where autocleanup can’t keep up and/or manual cleanup is taking significant time, you can add the index and see if it helps and I have the process enumerated below. Keep in mind this is not guaranteed to fix all cleanup issues and it may still be necessary to run manual cleanup regularly. If you continue to have issues with cleanup feel free to create a ticket with us here at CSS to assist you and get specific data to your environment.

Read on for the index definition as well as some important notes about whether you might need it.

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Apache Flink Table Store

Published 2022-05-19 by Kevin Feasel

Jingsong Lee and Jiangjie Qin have an announcement:

As of now it is quite common that people deploy a few storage systems to work with Flink for different purposes. A typical setup is a message queue for stream processing, a scannable file system / object store for batch processing and ad-hoc queries, and a K-V store for lookups. Such an architecture posts challenge in data quality and system maintenance, due to its complexity and heterogeneity. This is becoming a major issue that hurts the end-to-end user experience of streaming and batch unification brought by Apache Flink.

The goal of Flink table store is to address the above issues. This is an important step of the project. It extends Flink’s capability from computing to the storage domain. So we can provide a better end-to-end experience to the users.

Click through to see how table storage works.

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Summarize in KQL

Published 2022-05-19 by Kevin Feasel

Robert Cain continues a series on KQL:

When data is analyzed, it is seldom done on a row by row basis. Instead, data analysts look at the big picture, looking at total values. For example, the total number of times the disk transfer counter is recorded for a time period may give an indication of disk utilization.

To aggregate these values with KQL, we’ll use the summarize operator.

Read on for plenty of demos.

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Left and Right Deep Hash Joins

Published 2022-05-19 by Kevin Feasel

Forrest McDaniel dives into the forest:

There’s a lot already written about left versus right deep hash joins. Unfortunately for us SQL Server nerds, “left” and “right” don’t make as much sense in SSMS query plans – those have a different orientation than the trees of database theory.

But if you rotate plans, you can see left and right that make sense (even if they still don’t match canonical shapes). Just follow the join operators.

Read on to understand the difference and what it means for query performance.

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T-SQL Order of Execution and Aliases

Published 2022-05-19 by Kevin Feasel

Joe Billingham explains why you can’t do that thing you want to do:

So, you have just written a query, hit execute and you have encountered an error: Invalid column name ‘[column name]‘.

The column you’ve used in your WHERE clause cannot be identified by its alias. You’ve defined it at the top of the query and used it fine previously as your ORDER BY condition, so why can’t the engine recognise it?

Read on for the answer. This is why some people I know have wanted a SQL-like language which runs in order of execution, so a query would start with the FROM clause rather than the SELECT clause. Languages like KQL do work that day, so there are examples in the wild.

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823/824 Alerts with SQL Server and VMware

Published 2022-05-19 by Kevin Feasel

David Klee loops us in on a tricky-to-catch problem:

We’ve been tracking a weird state with SQL Server virtual machines on VMware and possible warnings on database corruption while VM backups are running, largely centered around (but not isolated to) the tempdb database.

TLDR: We’ve now got a VMware KB article on this situation that you and your VM admins should read if you hit the condition and fall into the specifics listed below. Reference VMware KB 88201 for more details.

Read on for David’s thoughts and what to do if you hit this problem.

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Power BI Field Parameters

Published 2022-05-19 by Kevin Feasel

Matt Allington throws one in for free:

The May 2022 version of Power BI Desktop includes a very interesting and useful feature – Field Parameters. Today I will show you how to use this new feature illustrating with 3 (no, wait, 4) use cases – Chart Elements, Chart Axis, Table Contents and Permanent Ad hoc Hierarchies.

Read on to see how to use this preview feature in Power BI.

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Backups with Checksum

Published 2022-05-19 by Kevin Feasel

Chad Callihan tempts Betteridge’s Law of Headlines:

When you’re specifying WITH CHECKSUM as you’re backing up databases, SQL Server will use checksums to help catch any inconsistencies with pages. This seems like a setting that you should always use and would expect to be a default setting. So why doesn’t SQL Server include it by default?

Using the principle that a backup isn’t valid until it’s verified, CHECKSUM acts as a useful but not sufficient check.

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Azure Resource Locks

Published 2022-05-19 by Kevin Feasel

Craig Porteous explains the benefit (and pain) behind resource locks in Azure:

In theory, these are perfect for preventing accidental (or deliberate) deletion of resources in Azure. They don’t prevent the deletion of data though, only operating at the “control plane” of a resource. That still sounds great though. Turn them on everywhere! That’s another layer of security in your cloud data platform. Right?

Yeah, here’s where the pain comes in. I tried using resource group locks but there are some resources which use delete capabilities, such as Azure Media Service. A delete lock means no ability to delete uploaded videos.

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