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SQL Server Partitioning an Active Table with Truncate
There are a number of interesting capabilities that get added in almost every new version of SQL Server for performance and scalability needs. As these features get added, they are often underappreciated and sometimes hardly used at all by many developers. One such feature that I have been tracking for close to ten years is Partitioning with SQL Server. When it first surfaced in SQL Server 2005, there was enough hype around this capability that it matured, eventually becoming one of the silver bullets I use with my customers. For mission critical large databases, this is a killer feature everyone should explore.
If you ask me, when SQL Server 2016 was released, I didn’t think there was much that could be done to enhance the capabilities of Partitioning. But in the most recent version, there has been an interesting addition that was added –the ability to Truncate a specific partition.
Why is this important? The premise for this feature is that we have the unique ability to partition data based on some state / date range. Many times it is important to remove unwanted data that has become stale after a period of time. A typical example is to remove the transaction records from a table which contains data more than three years old. If these data are not used or can ever change, DBAs always want an easy way to remove these records without using the DELETE statement. This is because the DELETE statement would bloat the Log files and if the amount of data is large, the table can easily get locked out blocking queries running on the table.
This is where partitioning comes in. Personally, I see this as an awesome addition to SQL Server 2016 that makes such critical processes seamless from an archival / removing dead data requirements.
Let me show you the construct you can use to visualize how this works. Here, I am showing you the number of rows in various partitions and then after the truncate statement, we can see only a specific partition rows have been cleared.
SELECT partition_id, partition_number,rows
-- Works from SQL 2016 only
TRUNCATE TABLE dbo.Partioned_Table WITH (PARTITIONS(2));
--- Verify Rows Deleted in Partitions
SELECT partition_id, partition_number,rows
The output for this would look like:
In this example, we have cleared just a single partition. The same can be done to clear multiple partitions using the following construct.
TRUNCATE TABLE dbo.Partioned_Table WITH (PARTITIONS(1,2,3,4));
If you have continuous partitions to be cleared, we can do this by using a range type of construct. A typical script for this would look like:
TRUNCATE TABLE dbo.Partioned_Table WITH (PARTITIONS(1 TO 4));
As you can see there are a number of ways we can use the TRUNCATE with Partitioned Tables in SQL Server 2016. I am sure you will find it useful and use it in your environments too, as you upgrade to SQL Server 2016.
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