Compressing Open Row Groups

If you’re using, or at least read up on Clustered Columnstore Indexes then you’ll know that the data is stored in segments. You’ll also know that there are 4 states the segments can be in at any one time:

How To Split Non-Empty Partitions When A Clustered Columnstore Index Exists on The Table

Another pithily titled blog post, but this one revisits the feature of SQL Server 2014 that piqued my interest the most: Clustered Columnstore Indexes. I’ve been working with Clustered Columnstore Indexes for the past few months and recently a colleague had to split a non empty partition, only for the error message below to appear.

Msg 35346, Level 15, State 1, Line 390 SPLIT clause of ALTER PARTITION statement failed because the partition is not empty. Only empty partitions can be split in when a columnstore index exists on the table. Consider disabling the columnstore index before issuing the ALTER PARTITION statement, then rebuilding the columnstore index after ALTER PARTITION is complete.

Ok, so it looks like we cannot split non empty partitions with a Clustered Columnstore Index on the table, or at least an enabled clustered columnstore index. So the topic for todays post is to find out how can we split a non empty partition when a clustered columnstore index exists on the table. We can create a test database/tables/Clustered Columnstore Indexes and disable the indexes before we split to see if that is the solution, as suggested in the error that it might be. Let’s start at the beginning using the database I created for my previous post on SQL Server 2014 Clustered Columnstore Indexes and Partitioning. The script below will create the database and the objects necessary. I’m going to state the obvious, but read through the scripts first before you run them; things like file locations on boxes are always different:

Cumulative Updates - SQL Server 2014 CU2

As part of their Incremental Service Modelling, no sooner have they released SQL 2014 RTM, Microsoft have now released SQL Server 2014 Cumulative Update #2.

SQL Server 2014 Clustered Columnstore Indexes and Partitioning

(If you attended my talk at SQL Supper in January 2016 and want a copy of my scripts, then this post here has the full details)

One of the features of SQL 2014 which got less column inches (pun intended) than Hekaton/ in memory OLTP but was of more interest to me was the clustered columnstore indexes, or CCI for brevity.