Author Archives: Bobby

You got to love Exadata and subpartitioned tables.  We have these queries on one particular table that are taking forever to parse.  Sometimes a simple explain plan on the simplest possible query against the table takes 20 or 30 seconds.  … Continue reading →

I’ve been working on testing performance on a database that uses Delphix as its storage system and ran across an unexpected side effect of using Delphix to clone a production database for testing.  Because Delphix uses NFS to present the … Continue reading →

I haven’t figured out the best way to do this yet so this is a work in progress.  I’m trying to document the process of taking a large query that joins many tables together and breaking it into a series … Continue reading →

I had a situation today where I had two slightly different queries that I thought should have the same plan but they didn’t.  So, I needed a way to force the slower query to run with the same plan as … Continue reading →

Most recent version here(updated). Added these two: display_results(test_name,compared_to_test_name) – output results of testings in the two scenarios.  List results from all queries that ran more than 3 times as long with one test or the other.  Also summarize results with … Continue reading →

Quick update to package from previous post. Here is the zip of the download: zip(updated) I added these procs to collect select statements on a source production database and to copy them back (as clobs) to the test database: collect_select_statements(max_number_selects, … Continue reading →

I’ve uploaded this package(updated) that I’m using to test some large select statements.  See the file packagedescriptionv1.txt for a description of the package.  Also, test.sql and test.log is an example of using the package. This is an updated version of … Continue reading →

This weekend we had the most convincing evidence that our change from dedicated to shared servers on a database that supports a farm of web servers was the right move.  We have had some outages on the weekend caused by … Continue reading →

I’m trying to test some select statements that have some lines longer than 4000 characters and I couldn’t get them to run in sqlplus so I built this proc to run a select statement that is stored in a CLOB … Continue reading →

One of our senior developers found a way to greatly improve the performance of a query by adding a dynamic sampling hint for a table that had multiple correlated conditions in its where clause.  This led me to try to … Continue reading →