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November 2018

Add ORDER BY to make ANY query faster

Yes it’s SCBT day here in Perth!

SCBT = Silly Click Bait Title Smile

This post is just a cautionary tale that it is easy to get caught up judging SQL performance solely on a few metrics rather than taking a more common sense approach of assessing performance based on the true requirements of the relevant component of the application.  I say “true requirements” because it may vary depending on what is important to the application for a particular component.

Interval versus Range partitions

One of the nice things about partitioning in the database is that partition pruning can quickly eliminate the requirement to read large amounts of data when the partitioning key(s) are appropriately provided in your queries (and DML). This also extends to queries where the values provided do not map to any partitions.

Here’s a simple example of a range partitioned table which only cover the values from (less than) 1 to a ceiling of 6.

FIRST_ROWS_10 CBO Is Hopeless, It’s Using The Wrong Index !! (Weeping Wall)

There’s an organisation I had been dealing with on and off over the years who were having all sorts of issues with their Siebel System and who were totally convinced their performance issues were due directly to being forced to use the FIRST_ROWS_10 optimizer. I’ve attempted on a number of occasions to explain that their […]

UKOUG Tech 18

One month to go before the big event in Liverpool. so I’ve been browsing the agenda to get some idea of the talks I’ll probably go to. At present this is what my list looksl like:

From production to test in a minute

How to create test data just like your production data without moving or copying your actual data.

From production to test in a minute

How to create test data just like your production data without moving or copying your actual data.

The Openworld Mega-Download!

If you are sad and pathetic enthusiastic and interested in content like me, once a large conference like OpenWorld is over, I like to have the content (slides etc ) from not just the sessions I attended, but all of the sessions I could not attend. In fact, I typically would like to have any and all available content, because that is probably the next best thing to attending the conference.

In particular, now that many of the sessions are streamed and/or capture for on-demand replay, either on the OpenWorld site directly, or via the Oracle Developers Youtube channel, the slides can then be viewed along with the presentation that drove them.

Join Cardinality – 5

So far in this series I’ve written about the way that the optimizer estimates cardinality for an equijoin where one end of the join has a frequency histogram and the other end has a histogram of type: