teradatatuning.blogspot.com
PRISE Teradata Database Optimization: April 2014
http://teradatatuning.blogspot.com/2014_04_01_archive.html
PRISE Teradata Database Optimization. Thursday, April 17, 2014. Sponsored by PRISE Ltd. How to use querybanding in Teradata? Teradata is a diligent RDBMS that runs sometimes millions of SQLs a day. You will see them in the DBQL (DataBase Query Logging area) - if it is switched on - but it's a hard job to know around. In that mess of queries. How can I find a specific query? What did that query run by? If I want to analyze or modify something I need to find the source of the execution as exactly as can be.
teradatatuning.blogspot.com
PRISE Teradata Database Optimization: November 2013
http://teradatatuning.blogspot.com/2013_11_01_archive.html
PRISE Teradata Database Optimization. Friday, November 29, 2013. Sponsored by PRISE Ltd. How to "re-parallelize" skewed joins. Assume that we have 1M customers, 4M transactions and our top customer produce the 2.5% of all transactions. Others produce the remaining 97.5% of transactions approx. evenly. Scroll down to the bottom of the post for sample table and data generator SQL. Our task is to join a "Customer" and a "Transaction" tables on Customer id. SELECT Customer name, count(*). GROUP BY 1;. RowHas...
teradatatuning.blogspot.com
PRISE Teradata Database Optimization: January 2014
http://teradatatuning.blogspot.com/2014_01_01_archive.html
PRISE Teradata Database Optimization. Monday, January 13, 2014. DBQL analysis III - Monitor "collect statistics". Sponsored by PRISE Ltd. Analyze "collect statistics" in DBQL. Please note that the solutions found in the article works on the DBQL logs, which covers only that users' activity, for whom the logging is switched on. Object" and "SQL" option in DBQL is required "on" to use the scripts provided. This article is applicable up to V13.10. W/o modifications, statistics handling changed from V14.
teradatatuning.blogspot.com
PRISE Teradata Database Optimization: Using Partitioned Primary Index II
http://teradatatuning.blogspot.com/2014/04/using-partitioned-primary-index-ii.html
PRISE Teradata Database Optimization. Thursday, April 03, 2014. Using Partitioned Primary Index II. Sponsored by PRISE Ltd. How to choose partitioned primary index (PPI). This post is an expand to my PPI basic. What is the difference between NPPI and PPI? NPPI: Non partitioned primary index. The good old regular PI. The rows are distributed by HASHAMP(HASHBUCKET(HASHROW(PI) ), and ordered by HASHROW(PI). PPI: Partitioned primary index. What is PPI good for? Proper random sampling is more complex, since t...
teradatatuning.blogspot.com
PRISE Teradata Database Optimization: March 2014
http://teradatatuning.blogspot.com/2014_03_01_archive.html
PRISE Teradata Database Optimization. Tuesday, March 18, 2014. Sponsored by PRISE Ltd. How to store date and time info effectively. Data Warehouse databases usually contain significant amount of date/time information. Physical modeling technique can seriously influence their storage space and usability. Date/time information can be stored in different ways/data types, each of them will have its own specialities. Timestamp(n) , when n means the fractional digits of seconds. Separate storage: Date and Time.
teradatatuning.blogspot.com
PRISE Teradata Database Optimization: September 2013
http://teradatatuning.blogspot.com/2013_09_01_archive.html
PRISE Teradata Database Optimization. Wednesday, September 25, 2013. Boost slow (LEFT/RIGHT) OUTER JOINs. Sponsored by PRISE Ltd. How to optimize slow OUTER JOINs. We have a (LEFT or RIGHT) OUTER JOIN, and it runs a long time while causing skewed CPU / Spool usage. In practice most of the time during the query execution only 1 AMP will work, while others have nothing to do, causing poor parallel efficiency. In the DBQL you should find skewed, high CPU usage queries (. Select Table1.x,Table2.y. If Table2 ...
teradatatuning.blogspot.com
PRISE Teradata Database Optimization: February 2014
http://teradatatuning.blogspot.com/2014_02_01_archive.html
PRISE Teradata Database Optimization. Friday, February 28, 2014. Sponsored by PRISE Ltd. How to use Join Index (JI) in Teradata. Join index is most like a "materialized view", say it is a stored result of an SQL SELECT ,. Like a table: you can define the primary index (PI) of the stored result. What are the main differences between a JI and a Secondary Index. Different internal structure and purposes. Appears as separate object (not a sub-table) in the DBC tables/views. Used in the JI definition. This is...
teradatatuning.blogspot.com
PRISE Teradata Database Optimization: December 2013
http://teradatatuning.blogspot.com/2013_12_01_archive.html
PRISE Teradata Database Optimization. Monday, December 30, 2013. Sponsored by PRISE Ltd. How to eliminate product joins. What is product join? Product join is one of the implementation methods of an SQL JOIN operation. Do not mix up with cross join (Cartesian product), which is one type of SQL joins. SQL join types, eg.: inner join, left outer join, full outer join, cross (Cartesian) join. Join implementation types, eg.: nested join, merge join, hash join, product join. Why don't we like it? Product join...
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