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What Are Hints?
22 Dezember 08 08:43 | Striving for Optimal Performance

Yesterday, while reading a swiss italian dialect tranlation of Le petit prince (entitled Ul principe pinin), I noticed a very interesting discussion between the little prince and the king (the inhabitant of the first planet visited by the little prince…...

Abgelegt unter: TOP, Query Optimizer

Automatic Evolution of SQL Plan Baselines
10 Dezember 08 05:00 | Striving for Optimal Performance

In the section Evolving SQL Plan Baselines of TOP (pages 299-300) I explain what an evolution is and how to manually do it. What I do not cover is the automatic evolution. In fact, I wrote only the following text about it: “In addition to the manual...

Abgelegt unter: TOP, 11gR1, Query Optimizer

Query Optimizer 11g – What’s new?
02 Dezember 08 10:01 | Striving for Optimal Performance

Today I presented at the DOAG Conference in Nuremberg. As the title of this post suggests, I talked about the query optimizer features introduced in Oracle Database 11g. This is an evolution of the paper I already presented at the UKOUG Conference in...

Abgelegt unter: 11gR1, Query Optimizer, Speaking

DBMS_XPLAN.PREPARE_PLAN_XML_QUERY
21 November 08 12:11 | Striving for Optimal Performance

As of 11.1.0.7 in the package dbms_xplan there is a new function: FUNCTION prepare_plan_xml_query(plan_query IN VARCHAR2) RETURN VARCHAR2; Simply put, the function takes as input a query that extract information from a plan table (e.g. plan_table or v...

Abgelegt unter: 11gR1, Query Optimizer

Invisible Indexes and Hints
11 November 08 05:02 | Striving for Optimal Performance

In this post I would like to remove some misinformation about the utilization of hints with invisible indexes. Let’s start by providing you what two sources say about that topic: Oracle Database 11g: New Features for DBAs and Developers (by Sam R. Alapati...

Abgelegt unter: 11gR1, Query Optimizer, Indexes

Bloom Filters
26 September 08 06:24 | Striving for Optimal Performance

Oracle Database, as of 10g Release 2, uses bloom filters in various situations. Unfortunately, no information about their usage is available in Oracle documentation. For this reason, I decided to write a paper to explain not only what bloom filters are...

Abgelegt unter: 11gR1, 10gR2, Query Optimizer

Long Parses and SQL Plan Baselines
11 September 08 11:36 | Striving for Optimal Performance

Few days ago, in the post entitled Long Parses, I pointed out that stored outlines can be used to shorten the parse time by restricting the number of execution plans considered by the query optimizer. As of Oracle Database 11g, stored outlines are deprecated...

Abgelegt unter: 11gR1, Query Optimizer

Long Parses
31 August 08 12:21 | Striving for Optimal Performance

From time to time I have to fight against long parses. In this post I would like to share with you what happened to a customer of mine while upgrading from 9.2.0.7 to 10.2.0.3 (10.2.0.4 was not yet available at that time). The parse of a complex SQL statement...

Abgelegt unter: 10gR2, Query Optimizer, 9iR2

SQL Profiles in the Data Dictionary
19 August 08 09:40 | Striving for Optimal Performance

In the paper SQL Profiles (page 22) I described the data dictionary tables where the hints belonging to SQL profiles are stored. For example, with the following query it is possible to display the hints associate to the SQL profile named opt_estimate...

Abgelegt unter: 11gR1, 10gR2, 10gR1, Query Optimizer