May 2014

Comparison of Columnstore Compression

SQL Server 2012 introduced non-clustered columnstore indexes, and SQL Server 2014 gave us clustered columnstore indexes. Both share the same technology for performance boosts, and they both share the same algorithms for compression. However, the compression will depend on the data you are storing. SQL Server uses a mechanism of row groups, segments, encoding and compression to store the data for columnstore indexes. First the data is horizontally divided into row groups, where each group contains approximately 1 million rows. Next, the row groups are vertically partitioned into segments, where each column of the table is its own segment. Those...

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