Our Problem

In a shared in environment you may have hundreds of databases with the same schema but depending on the data loaded into them not all of them will benefit from being compressed so you don’t want to incur the overhead of compression on all the of the data.

Our Solution

We can write procedure check periodically rather a table will benefit from compression or not.  There are a few tricks though:

  1. If you have sparse columns you cannot compress the table, we check for that in lines 70-74.
  2. Next if is a index type of 1 (a clustered index) it cannot contain LOB data types image, ntext, or text.  Which these days shouldn’t be a problem, they have been after all deprecated, so you aren’t using them.  We check for these in lines 76-84.
  3. Finally, we perform the same test for LOB data on index type of 2 (nonclustered indexes) in lines 85-95.

If everything checks out OK we call our second procedure to calculate the percentage of space we would space and if we would save more than 25% then we create script to compression the index.  Now we have a @Debug parameter in here so it can just show us what code it would execute to determine what it will do.

NOTE: This objects are created in a DBA database if you create them in a different database you will need to edit line 99 in the first procedure to indicate which database you placed the procedures in.

Finale

Things I could be see be added is logging when an index is compressed to a table so if something happens to performance you could correlate it back to this event.  You may also not want to hard code the value of 25 percent.  Also in the first procedure you may want to have a way to tell it which databases you want it to consider for operation.  We actually have our procedure where it doesn’t do every database just the once that have identical schemas but different customer data.

 

Tracy Boggiano
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Tracy Boggiano

Database Superhero at ChannelAdvisor
Tracy has spent over 20 years in IT and has been using SQL Server since 1999 and is currently certified as a MCSE Data Management and Analytics. She has worked on SQL Server 6.5 and up including currently SQL 2017 RC1. She enjoys monitoring, performance tuning, and high availability and disaster recovery technologies. Tracy is currently a co-organizar the for special interest group for Advanced DBA Topics for the TriPASS user group.

She also tinkered with databases in middle school to keep her sports card collection organized.

Tracy has volunteered through the NC Guardian ad Litem program since 2003 advocating for abused and neglected foster children in court.This is her passion outside of SQL Server and favorite job.More information about this program in North Carolina can be found at http://volunteerforgal.org or the national organization CASA at http://www.casaforchildren.org.
Tracy Boggiano
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