Archive for the ‘Execution Plans’ Category
Thursday, August 14th, 2008
Note: Originally this experiment was from a post I wrote on the Oracle Forum: Database - General. I recommend that you read Jonathan Lewis' summarization of the thread instead of reading all 671 posts (as of today). You will spend much less time and get more out ...
Posted in Data Warehousing, Execution Plans, Optimizer, Oracle, Performance | 10 Comments »
Thursday, May 29th, 2008
Recently I was reading this thread, "Trying to make use of bitmap indexes" on the Oracle Forum. Before I had finished a working example, Jonathan Lewis had posted his response which was on par with my thoughts. Since this is a topic I see frequently, I thought ...
Posted in 10gR2, 11gR1, Data Warehousing, Execution Plans, Optimizer, Performance, SQL Tuning, Statistics, Troubleshooting, VLDB | 6 Comments »
Thursday, May 22nd, 2008
Recently someone showed me a query execution plan with an operation of HASH JOIN ANTI NA. At first, it was thought maybe it was a bug and the operation had a type-o in it, but after further research it was discovered it was a valid operation and a new ...
Posted in 10gR2, 11gR1, Data Warehousing, Execution Plans, Optimizer, Oracle, Performance | 7 Comments »
Wednesday, March 26th, 2008
Recently the Oracle Optimizer Development Team put out a White Paper entitled Upgrading from Oracle Database 9i to 10g: What to expect from the Optimizer. This paper discusses the main differences between 9i and 10g in the subject area of the Optimizer and Statistics. As G.I. Joe ...
Posted in 10gR2, Execution Plans, Optimizer, Oracle, Statistics, Troubleshooting | 16 Comments »
Wednesday, March 5th, 2008
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 ...
Posted in 10gR2, 11gR1, Data Warehousing, Execution Plans, Optimizer, Oracle, Performance, SQL Tuning, Statistics, VLDB | 11 Comments »
Monday, February 18th, 2008
A few months ago the Oracle Optimizer Team did a blog post entitled Outerjoins in Oracle. In the Lateral View section of that post they go through some examples and discuss how a query is transformed with the ANSI outer join syntax. I thought it would be useful ...
Posted in Execution Plans, Optimizer, Oracle, SQL Tuning, Troubleshooting | 16 Comments »
Sunday, January 6th, 2008
Many times a DBA wants to know where a SQL statement is in its execution plan and where the time is being spent. There are a few ways to find out this information, but an 11g new feature makes gathering this information extremely easy. Oracle 11g Real-Time SQL Monitoring ...
Posted in 11gR1, Execution Plans, Oracle, Performance, SQL Tuning, Troubleshooting | 5 Comments »
Wednesday, January 2nd, 2008
I've been working on a few test cases and I'm in search of some real-world data. If your production Oracle database uses system statistics, either Workload Statistics or Noworkload Statistics, and you are willing to share them, please post a comment with the output from the following two ...
Posted in 10gR2, 11gR1, Execution Plans, Optimizer, Oracle, Performance, SQL Tuning, Statistics | 29 Comments »