Index Maintenance is an important aspect of database health. Above and beyond regular index rebuilds and reorganizations it is important to understand the usage of the indexes on your database. Cleaning up unused indexes can save a lot of overhead on Insert/Update/Delete operations. To achieve that goal, I typically run a script like the one shown below and check out whether or not an index has had any seeks or scans against it as a starting point in my cleanup regiment. SELECT d.name, OBJECT_NAME(i.[object_id]) AS [ObjectName], i.[name] AS [IndexName], s.user_seeks, s.user_scans FROM sys.indexes AS i LEFT OUTER JOIN sys.dm_db_index_usage_stats AS s ON i.[object_id] =…
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What is Azure SQL Database Serverless? When I hear the term serverless my mind gets confused. How can a database exist without a server? Azure is a cloud platform, is my database just floating in the air? No, I am not really thinking that, but still the word serverless can be hard to understand. So, let’s walk through what it is. Serverless is a term commonly used for function as a service patterns like Amazon Lambda, or Azure Functions, where you have a piece of code that is called and executed without you deploying any infrastructure. Azure Logic Apps are another version of this—a program that exists to do a…
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Under compatibility level 150, in both SQL Server 2019 and Azure SQL Database, you now can use batch mode for CPU-bound analytic type workloads without requiring columnstore indexes. There is no action needed to turn on batch mode aside from being on the proper compatibility mode. You also have the ability to enable it as a database scoped configuration option (as shown below), and you can hint individual queries to either use or not use batch mode (also shown below). If you recall in my earlier blogs on columnstore, it is batch mode in conjunction with page compression that drastically increases query performance. This feature, Batch Mode on Rowstore, allows…
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Knowing your data is very important when it comes to writing code. Now I’ll admit that I am very far from being a developer, however as a DBA, I spend much of my day’s performance tuning code. In doing so, I get to see many ways code can introduce excess database reads. One of the most recent things I have come across has to do with NULLs. The environment I was working in had no default values in their table design, so it was riddled with NULL values. Over the years they had implemented coding standards to try and mitigate these NULL values within their code. In every column search…
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Every day, more IT organizations decide to move their SQL Server databases to Azure. In fact, over a million on-premises SQL Server databases have been moved to Azure. There’s an interesting blog about how Microsoft is faster and cheaper than its competitors that’s worth a read. To assist with your move to Azure Microsoft offers a number of migration tools and services to make this move as smooth as possible which I think attributes to their success. Two of those options are below with some informational links. If you’re migrating a number of large SQL Server instances, Azure Database Migration Service is the best way to migrate databases to Azure…
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Did you know that a native STRING_SPLIT function built into SQL Server was added into SQL Server 2016? As a consultant I see so much code that call out to a scalar function that are used to split out string delimited variables into a usable list. For those that use this method I suggest you look at this function. STRING_SPLIT is a table valued function that returns a single column of your string values split out by the delimiter. This is an unusual bit of T-SQL, in that compatibility level 130 or higher is required for its use (Microsoft didn’t want to induce breaking changes into existing user code). Using…
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We know that sorting can be one of the most expensive things in an execution plan as shown below. However, we continue to do ORDER BYs repeatedly. Yes, I 100% agree that there is a need to sort a results set and that this should be done in the procedure for good reason, but my concern is having multiple sorts, erroneous sorts, and the sorts that can be done elsewhere. These are the ones that waste resources and can stifle performance. Many of us writing procedures tend to write in code blocks. We write the SELECT, JOINS, FROMs and WHERES then immediately follow it up with and ORDER BY as…
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Now that I have written about In-Memory Tables and Migrating to In-Memory tables, let’s look at indexes and how they are created and how they work within those tables. As you can imagine indexes, called memory optimized indexes are different for these types of tables, so let’s see just how different that are from regular tables. Before we dive into this subject it is VERY important to note the biggest differences. First, If you are running SQL Server 2014 memory optimized indexes MUST be created when the table is created or migrated. You cannot add indexes in an existing table without dropping and recreating the table. After 2016 you now…
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Previously I wrote about In-Memory Optimized Tables, in this blog I am going to discuss how to determine which tables could benefit from being In-Memory by using a tool called Memory Optimization Advisor (MOA). This a is a tool built into SQL Server Management Studio (SSMS) that will inform you of which tables could benefit using In Memory OLTP capabilities and which may have non supported features. Once identified, MOA will help you to actually migrate that table and data to be optimized. Let’s see how it works by walking through it using a table I use for demonstrations in AdventureWorks2016CTP3. Since this is a smaller table and doesn’t incur…
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Sometimes when I try to learn about a concept my brain blocks out everything about it. Talking about anything that uses the “In Memory” concept tends to do this to me on occasion. It’s important to note that “In Memory” is a marketing term for a series of features in SQL Server that have common behaviors but are not inherently related. So, in my next few blogs I am going to attempt to explain some In-Memory concepts as it relates to SQL Server starting with a dive into Memory Optimized Tables. I’ve already written about Columnstore which has vastly different use cases to In Memory OLTP, and you can find…
