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New DBQL logging options USECOUNT and STATSUSAGE, introduced in Teradata Database 14.10, enable the logging of used and missing statistics. The output of this logging can be utilized to find used, unused, and missing statistics globally (for all queries) or for just a subset of queries.
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08 Jan 2015
| 32 comments
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Managing Teradata Optimizer statistics can be labor intensive and error prone. Many users struggle to know what columns and indexes to collect statistics on, how to detect and prevent statistics from becoming stale, and how to know if collected statistics are being used.
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12 Jun 2014
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Hi Guys,
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15 Apr 2014
| 2 comments
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This presentation builds on Recorded Webcast # 49911 Explaining the EXPLAIN, which did just that (if you have not viewed, please do so before watching this webcast).
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17 Mar 2014
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Hi All,
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25 Dec 2013
| 2 comments
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Hi.
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23 Jul 2013
| 4 comments
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Hi all, I'm having some performance issues due to the way certain queries are being processed by the optimizer. I have a set of views that I want to join together, and each of these views has the same JOIN/WHERE clause combination:
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25 Jun 2013
| 1 comment
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You would expect the other way around .... Optimizer can make estimates that are thrown off the real count based on so many factors.
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21 Dec 2012
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Good Day Folks...
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15 Dec 2012
| 2 comments
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estimated cardinality for the following predicate towards timestamp column is far too high vs date column 1) Table DDL: --------------------------------------
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12 Jul 2012
| 7 comments
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Statistics about tables, columns and indexes are a critical component in producing good query plans. This session will examine the differences between random AMP sampling, full statistics collection, and USING SAMPLE collection, and will share details about how each of these 3 approaches works internally. Statistics histograms, their uses and limitations, will be explored. You'll get some insights into collecting statistics on multiple columns, on indexes, on and on the system-derived column PARTITION. Statistics extrapolation will be touched on briefly, and the session will wrap up with some general recommendations for collection statistics.
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01 Apr 2011
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Hi, I am new to Terra Data. I have complex queries that are retrieving data from different tables and using different joins. Also, i have to apply some conditions to clean the duplicates and time period checks.
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19 Feb 2010
| 1 comment
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The way I thought Teradata always work is trying to keep things "local" to amp. Therefore, if A Join B on column C , the table A and Table B will be retrieved with not null on C and redistribute on hashcode of C and then join , do I under stand this right? (well of course, there are situations that you like to do duplicate to all amps in case one table is too small). The idea is that table needs to be distributed by hash of equal join column and then the data will resides on the same amp and they can perform join operation.
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03 Feb 2010
| 10 comments
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I gave a presentation at the Teradata Partners Conference last week on the fundamentals of collecting statistics, where I touched briefly on the rules behind confidence levels. I’m using this article to go into further depth, and offer you more examples of how these confidence levels come about.
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28 Oct 2009
| 6 comments
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Cached plans are good. For repetitive queries, cached plans remove the overhead of parsing and optimizing, and this helps short work perform more consistently.
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05 Aug 2009
| 14 comments
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Have you ever had what looks like a great query plan turn into life in the slow lane at run time?
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12 Jun 2009
| 29 comments
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