Voice of the DBA

Author: way0utwest

  • Distributed SQL Databases

    One of the challenges that SQL Server, and many RDBMSes, face is scaling out. While SQL Server can grow to handle a large workload on one piece of hardware, eventually there reaches a point when a single machine cannot handle the workload.

    Microsoft is trying to handle this with some new tricks. We have the Hyperscale editions of Azure SQL Database and Big Data Clusters, on premise. I don’t know that either of these will end up providing us with scale out for our OLTP databases, but they are options.

    There are other options. Google has Spanner, which is a distributed SQL database and CockroachDB has attracted some attention. I caught an article that talks about some of the reasons you might look at CockroachDB, which is a cloud system, but one that gives you scale, and perhaps more importantly, lack of lock-in with a cloud vendor.

    I don’t know all the ins and outs of a distributed, scalable SQL database, but I do know that scaling one table, with lots of concurrent access, can be tricky. There are improvements in bandwidth and technology that might allow things to scale well, but I can’t help but think that conflict resolution will be a challenge if many people need to write to the same rows.

    I also know that often we aren’t writing to the same rows, but to the same table. Distributing that is easier, but when we start to look at lots of tables with referential integrity, I wonder how scalable this is. After all, the data needs to get committed and then written to multiple places for this to work well.

    The one advantage in the cloud is throwing hardware at problems like this, often in a more cost effective way than an organization can do in their own data center. Whether this works well remains to be seen, but certainly there are customers and investors that see this as a part of the future.

    Steve Jones

  • T-SQL Tuesday #136–The Datatype Blog

    tsqltuesdayIt’s that time of the month again, and this time it’s an interesting topic. The invitation is from Iceland, where Brent Ozar has relocated for the foreseeable future. I’m slightly jealous, and wish I could go visit. I enjoy winter, and the pictures he’s posted look amazing. Definitely a bucket list trip for me.

    However, this month, he’s asking about data types. Are there some you love or hate, and I’ve got a thought on this. In case you wonder, there is a list, broken into types. Apparently MS went into a “categorize everything” frenzy in the docs, which is OK, but I often don’t intuit the way they’ve broken things down. I wish they kept a long list on a page somewhere that was easy to find.

    Naming Confusion

    It has been deprecated, but the timestamp type is still around. It’s not in the list, but it is mentioned as a synonym for rowversion. This is a unique binary number in each database, which is often used to detect changes in a row. If you have two people editing a row, and a change updates a rowversion column, then each can detect if that value is different from the original one. Handy in terms of client side conflict resolution, which can prevent last-writer-wins scenarios for applications.

    I haven’t seen it used lately, but in the 90s and early 2000s, I often saw code that checked this before letting a user make an update in some data entry application. However, this was often a “timestamp” column, which was constantly confusing to me as a DBA or developer. I kept thinking I’d get some sort of datetime stamp in there, rather than a binary value.

    This shouldn’t be a problem in the future, as timestamp isn’t really doc’d, though timestamp can be found on Google searches. 

    The other reason I dislike this type is that we can’t change it to rowversion. An ALTER TABLE … ALTER COLUMN doesn’t work.

  • Daily Coping 9 Mar 2021

    I started to add a daily coping tip to the SQLServerCentral newsletter and to the Community Circle, which is helping me deal with the issues in the world. I’m adding my responses for each day here. All my coping tips are under this tag. 

    Today’s tip is to start today by appreciating your body and that you’re alive.

    I spend a lot of time working on my body, getting exercise and movement, trying to stay fit for the future. I’m not as good with my diet, but I’m trying.

    In any case, I have some hard days. My body is sore, or as I age, different parts just hurt. In the last year, I’ve had days where I struggled to get comfortable or even walk.

    However, I appreciate that I’m fairly healthy, I can practice yoga, weight lift, or ski, as I did last week. I’m grateful I’m alive and well, when far to many have lost their lives in the last year.

    I’m taking a few minutes today to appreciate where I am and that I am here.

  • Logging Messages with Raiserror – #SQLNewBlogger

    Another post for me that is simple and hopefully serves as an example for people trying to get blogging as #SQLNewBloggers.

    I recently ran across some people discussing how to log some information in a script. One person was using PRINT, which I often use for quick checks, but someone else noted the RAISERROR works well, and you can customize messages.

    For example, I can have this type of script:

    DECLARE @d VARCHAR(20);

    -- do stuff
    

    SELECT @d = CAST( SYSDATETIME() AS VARCHAR(20));
    
RAISERROR('%s - something happened at this time', 0, 1, @d)

    This allows me to add information into an error message. I can certainly construct @d with other stuff and then use that in PRINT, but I could get out of order messages. If  I add NOWAIT, I can ensure my messages get returned immediately.

    There are lots of options with RAISERROR, which I still use in place of THROW at times. While I like THROW, I think it doesn’t always give me the options I want for error handling, such as logging to the Windows lots.

    SQL NewBlogger

    When I saw this, I realized that I didn’t know, or remember, some of the ins and outs of RAISERROR, so I spent a few minutes looking through docs and playing with the code. I then wrote this quick post to help me remember a bit more.

    Short and quick is a good way to structure posts. I didn’t walk about all the options or ways I can use things. I’ll do some of that in another post.