The accuracy of sample statistics has been greatly improved over the last Teradata releases. So I usually try to use sample stats on most of the big tables and I found them to be reliable on many columns, not only the officially recommended unique or nearly-unique columns, e.g. on DATEs.

Statistical information is vital for the optimizer when it builds query plans. But collecting statistics can involve time and resources. By understanding and combining several different statistics gathering techniques, users of Teradata can find the correct balance between good query plans and the time required to ensure adequate statistical information is always available.

This recently-updated compilation of statistics collection recommendations are intended for sites that are on any of the Teradata Database 14.10, 15.0, or 15.10 software release levels. Some of these recommendations apply to releases earlier than Teradata Database 14.10 and some rely on new features available starting in Teradata Database 14.10.  Statistics collection functionality in the Teradata Database works the same in 14.10, 15.0 and 15.10 releases.

For greater detail on collecting statistics for Teradata Database 14.10, see the orange book titled:  Teradata Database 14.10 Statistics Enhancements by Rama Krishna Korlapati.

Contributors: Carrie Ballinger, Rama Krishna Korlapati, Paul Sinclair, September 11, 2014

An earlier blog post focused on simple steps to get started using the Teradata 14.10 Automated Statistics Management (AutoStats) feature.  One of the new capabilities that AutoStats relies on when it streamlines statistics collection is the new “Threshold” option.  Threshold applies some intelligence about when statistics actually need to be re-collected, allowing the optimizer to skip some recollections.  

Although you will probably want to begin relying on AutoStats when you get to 14.10, you don’t have to be using AutoStats to take advantage of threshold, as the two features are independent from one another.  This post will give you a simple explanation of what the threshold feature is, what default threshold activity you can expect when you get on 14.10, and what the options having to do with threshold do for you.  And you’ll get some suggestions on how you can get acquainted with threshold a step at a time.  

I’ve mentioned it before, Marcio has blogged about it, customers have brought it up at the Partners Conferences. It’s cheap, fast, risk-free, with immediate results. But some of you are still not getting it. Or it could be you’re one of the few who truly don’t need it.

Collecting full statistics involves scanning the base table and performing a sort to compute the number of occurrences for each distinct value. For some users, the time and resources required to adequately collect statistics and keep them up-to-date is a challenge, particularly on large tables.

Please  note:  This posting is relevant only to software releases prior to Teradata Database 14.0.  Ignore this recommendation if you are on 14.0 or greater software.

You’re in a time crunch. Maybe you’ve got an undersized backup environment that is incredibly slow, or you just have important stuff happening and you need to keep the software upgrade window as short as possible.