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Teradata Cookbook

You're reading from   Teradata Cookbook Over 85 recipes to implement efficient data warehousing solutions

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Product type Paperback
Published in Feb 2018
Publisher Packt
ISBN-13 9781787280786
Length 454 pages
Edition 1st Edition
Languages
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Authors (3):
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Abhinav Khandelwal Abhinav Khandelwal
Author Profile Icon Abhinav Khandelwal
Abhinav Khandelwal
Viswanath Kasi Viswanath Kasi
Author Profile Icon Viswanath Kasi
Viswanath Kasi
Rajsekhar Bhamidipati Rajsekhar Bhamidipati
Author Profile Icon Rajsekhar Bhamidipati
Rajsekhar Bhamidipati
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Toc

Table of Contents (14) Chapters Close

Preface 1. Installation 2. SQLs FREE CHAPTER 3. Advanced SQL with Backup and Restore 4. All about Indexes 5. Mixing Strategies – Joining of Tables 6. Building Loading Utility – Replication and Loading 7. Monitoring the better way 8. Collect Statistics the Better Way 9. Application and OPS DBA Insight 10. DBA Insight 11. Performance Tuning 12. Troubleshooting 13. Other Books You May Enjoy

How to collect statistics


In most cases, tuning a poorly performing query starts with taking a look at the collected stats on the tables involved. One wrong/stale stat, or no stats on tables, can turn a regular query into a shark query that eats up all resources on the system. Let's explore more about how and when to collect these statistics.

The following is the EXPLAIN plan of some query:

2) Next, we execute the following steps in parallel.
    1) We do an all-AMPs RETRIEVE step from SYSDBA.SITE_ID in view SYSDBA_VIEWS.SITES_IDV by way of an all-rows scan with no residual conditions into Spool 2 (all_amps) (compressed columns allowed), which is duplicated on all AMPs. The size of Spool 2 is estimated with high confidence to be 55,220rows (5,521,220 bytes).  The estimated time for this step is 0.05 seconds. 

If you need to retrieve statistics data on a system, there are a few tables in DBC where metadata for stats are stored, they are: 

  • DBC.ColumnStatsV: Gives stats information of ‘single’...
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