To mark the OTN Appreciation Day I’d like to offer this thought:
“Our favourite feature is execution plans … execution plans and rowsource execution statistics … rowsource execution statistics and execution plans … our two favourite features and rowsource execution stats and execution plans … and ruthless use of SQL monitoring …. Our three favourite features are rowsource execution stats, execution plans, ruthless use of SQL monitoring and an almost fanatical devotion to the Cost Based Optimizer …. Our four … no … amongst our favourite features are such elements as rowsource execution statistics, execution plans …. I’ll come in again.”
With apologies to Monty Python.
A question about parallel query and cardinality estimates appeared on OTN a little while ago that prompted me to write this note about helping the optimizer do the best job with the least effort. (A critical point in the correct answer to the original question is that parallel query may lead to “unexpected” dynamic sampling, which can make a huge difference to the choice of execution plans, but that’s another matter.)
The initial cardinality error in the plan came from the following predicate on a “Date dimension” table:
I rarely blog about anything non-technical but after the events last Friday (1st July) I wanted to say something about the pride that I shared with several hundred parents around the country as they saw the effect their offspring created through a living memorial of the terrible waste of life that happened a hundred years ago on 1st July 1916 when some 70,000 soldiers (a very large fraction of them British) were killed or injured on the first day of the battle of the Somme.
I published a note this morning that I drafted in January 2015, and I didn’t notice that it had gone back in time to publish itself on the date that I first drafted it – and it’s already been tweeted twice so I can’t move it. So this is a temporary link to pop it to the head of the queue while leaving it where it first appeared.
I received an email a few weeks ago asking me if I would look at a series of three posts on adaptive dynamic sampling in 12c – (part 1, part 2, part 3). I took a note of the topic and URLs, and read through them fairly rapidly, and they seemed to be perfectly reasonable articles describing the authors thoughts, tests, and observations.
So it’s that time of year when I have to decide on my timetable for the UKOUG annual conference. Of course, I never manage to stick to it, but in principle here are the sessions I’ve highlighted:
I don’t know why I ever agree to go anywhere near Doug Burns – he usually manages to persuade me into doing things I don’t want to. This time (at a meeting of the London Oracle Beer group) he’s persuaded me that I really should join twitter. So I have (jloracle) – and found that I was being followed by four people before I even created an account, and was advised that I’d really, really, like to follow:
I had no idea who Jack Rivera might be, though I did recognise the next three names from those annoying ads that seem to appear on all sorts of news feeds. The one that baffled me was Gwen Shapira – by what mechanism did twitter manage to connect my name/tag/email address with someone relevant ?
Anyway, thanks, Doug – now I have to start thinking of something intelligent, perceptive or witty in 140 characters or less.
The singer is Canadian astronaut Commander Chris Hadfield who has been tweeting and posting pictures from space – be careful, you may get hooked: https://twitter.com/Cmdr_Hadfield/status/332819772989378560/photo/1
When I posted the link to the video it had received 1.5M views; less than 24 hours later it’s up to roughly 7M. (And they weren’t all Richard Foote). Clearly the images have caught the imagination of a lot of people. If you have looked at the twitter stream it’s equally inspiring – and not just for the pictures.
I’m sure I wrote something a little while ago about cutting down on long-haul flights – but I’ve just been subjected to a positive barrage of invitations that I’ve found hard to resist. So my international travel itinerary for the future is starting to look like it might be a little busy. Probable highlights:
I’m aiming to take a short city-break in Moscow in May, and I’ll be stopping off with the people at Innova to spend a day talking about Oracle.
I’ve volunteered to take part in the southern leg of the “LA OTN” tour in August – aiming to visit Chile 01/08, Peru 03/08, Uruguay 06/08, Argentina 08/08, and Brazil 10/08 – flying home just in time for my son’s 21st birthday.
Then, in late October, I have an invitation to spend a couple of days in Beijing presenting at the All China Oracle User Group conference.
When people ask for help on (for example) OTN, they are often asked to supply further information – sometimes in the form of requests for results from SQL queries. If you are ever in this position, you may find that you don’t understand what the query does, or why the information is useful – nevertheless you can still do something to make it as easy as possible for your potential saviour to help you.
Here’s an example to show you how NOT to do it:
Request for information: “Please format the contents of v$sga_dynamic_components.”