I recently came across a query in which the Optimizer was making a poor cardinality estimate, which in turn caused inefficient join type, which in turn caused the query to run excessively long. This post is a reenactment of my troubleshooting. The Suspect SQL The original SQL was quite large and had a fairly...
Oracle OpenWorld 2007 has come and gone and from the Real-World Performance Group’s perspective we’d consider it a successful one. The content of this year’s presentations seems to have gone over quite well as shown by the number of hallway comments and emails we received. At least two Oracle bloggers have put up their...
In the Real-World Performance Roundtable, Part 2: The Optimizer, Schema Statistics, SQL Tuning at Oracle OpenWorld 2006, I worked an example of how the optimizer can have difficulty estimating the correct cardinality when there is data correlation. (The Zodiac example can be found on pages 46-49 of the presentation.) In Oracle 11g, there has...
Many of you are aware of the Oracle 11g Database New Features and while some may be generally interested in new features, one area that I focus on is new features that yield gains in performance. Some of these features can be found in the General Server Performance section of the Oracle 11g Database...
For those of you who will be attending Oracle OpenWorld 2007 and have interests in the database performance area, I would recommend to you to try and attend the Real-World Performance Group Roundtable session. The session starts with a brief “Hot List” of performance issues that have been predominant in the field over the...
Recently, I’ve been quite busy with performance projects and haven’t had the spare time I would like to keep up on my blog. Now that those projects are behind me, I wanted to blog about the use of one feature that made a significant difference in performance on a number of queries for this...
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