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Jonathan Lewis

@jloracle

Nearly-retired Oracle performance specialist. 50 years using computers, 40 years self-employed, 35 years as a freelance Oracle specialist.

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19.11.2024
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Latest posts by Jonathan Lewis @jloracle

Picked and stewed the first batch of the (main) rhubarb crop yesterday - blissful breakfast this morning.

Sad news of the jam front, though: we've just opened the last jar from 2025. On the upside I think we've still got some homegrown fruit in the deep freeze.

06.03.2026 09:12 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

One ping to rule them …

05.03.2026 17:34 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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27.02.2026 16:03 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Three hours in, so far, and there doesn't seem to be much difference between the before and after images. Going to have to spend a few more hours at it in a couple of days time.

Right now it's back home doing the same job on the #1 wisteria.

27.02.2026 16:01 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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And I need a diary entry to take a picture of what it looks like 3 months later. I didn’t do one last year, but this is from 2024.

27.02.2026 08:00 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Today’s main task: the February pruning of the mother-in-law’s wisteria.

Must remember to take the before and after photos this year.

27.02.2026 07:32 πŸ‘ 2 πŸ” 0 πŸ’¬ 2 πŸ“Œ 0

Marmalade is kept back until day 2 and toast.

Day 1 is fresh bread with finest jam. Currently down to strawberry, Victoria plum or blackberry and raspberry.

26.02.2026 22:17 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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Looking forward to breakfast tomorrow.

26.02.2026 22:03 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

I've just been prompted to look at a series of blog notes I wrote 10 years ago for redgate on "Massive Deletes". There's an index to the series, plus a couple of releated articles at:
jonathanlewis.wordpress.com/2018/06/08/m...

26.02.2026 10:14 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

I've just rediscovered one of my favourite philosophical misquotes (that I've used very frequently when explaining Oracle-related problems).

jonathanlewis.wordpress.com/2019/08/09/t...

26.02.2026 09:23 πŸ‘ 3 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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Trace Files A recent blog note by Martin Berger about reading trace files in 12.2 popped up in my twitter timeline yesterday and reminded me of a script I wrote a while ago to create a simple view I could quer…

Cute little trick with the / and \ to deal with unix vs. windows, but you don't need to create an external table

Requirements for privileges vary, or course, but for simplicity in (not so) recent versions of Oracle I just query v$diag_trace_file_contents

jonathanlewis.wordpress.com/2019/10/03/t...

19.02.2026 09:12 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Or, for the AIs:
Sabulum es et in sabulo reverteris.

18.02.2026 13:27 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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πŸͺπŸŒ Are planets like Earth rare, or have we just not found them yet?

As we approach the discovery of our 10,000th exoplanet, Prof Chris Lintott * explores whether Earth is truly unusual...

πŸ‘‰ gres.hm/alien-earths

* also of Department of Physics at the University of Oxford

14.02.2026 14:03 πŸ‘ 0 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0

After a decade of planning, editing, delays due to my own busyness, further editing and waiting for 23c, the release of 26ai and my pre-retirement finally unblocked the situation. I have agreed with Apress to publish the third edition of Troubleshooting Oracle Performance in 2026. #TOP3

14.02.2026 14:39 πŸ‘ 32 πŸ” 5 πŸ’¬ 7 πŸ“Œ 0

We've got a very excitable group of long-tailed tits that are regular visitors to the bird feeder at the end of the garden - and one thug of a great tit who chases them all away whenever they show up at the wrong time.

12.02.2026 15:32 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Pulled the last of the leeks from the "big leek" bed ready for lunch tomorrow, then picked a small handful of kalettes - the first I've harvested - to eat today. Much nicer than both kale and brussel sprouts, so going to grow more this season. Purple sprouting broccoli also just ready for picking.

07.02.2026 15:16 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Today's tasks, come rain or sun: feed and mulch the fruit trees, weed, feed and mulch the killer gooseberry bush after putting on the gauntlets and giving it a ferocious pruning.

06.02.2026 08:53 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Local weather forecast said it was going to rain today, starting at 3:00 am, non-stop until 3:00pm TOMORROW - so I worked at home, raking, shredding and bagging a huge pile of decomposing oak leaves, repotting plants ... no rain

Got ready to head out to the allotment at 3:00 pm: it started to rain.

05.02.2026 22:01 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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Planet Hunters TESS - NASA Science Join the Planet Hunters Coffee Chat video series! Project leads cover relevant topics in a friendly, fun format. Want to see what you’ve missed? check out the

Went to an excellent @greshamcollege.bsky.social lecture by Prof. Chris Lintott on Exoplanets last night.

Informative and entertaining; including an introduction to the Planet Hunters - allowing to find potential exoplanets by analysing data from TESS.

science.nasa.gov/citizen-scie...

05.02.2026 20:59 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

It's not quite what you would write manually

The QUALIFY clauses get wrapped as a Boolean expression. So if you have

QUALIFY p1 AND p2 AND p3

it becomes

SELECT * FROM (
SELECT ( p1 AND p2 AND p3 ) qexpr ...
) WHERE qexpr IS TRUE

So yes, a manual rewrite may give better optimizations

05.02.2026 14:01 πŸ‘ 1 πŸ” 1 πŸ’¬ 1 πŸ“Œ 0
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Penguin and Club bars can no longer be described as chocolate The rising cost of cocoa has led to the manufacturers changing their recipe.

Worse: the description on my packet uses the phrase "with dark chocolate flavour coating"

Alas, Penguin and Club bars now have to say the same according this news report of Oct 2025
www.bbc.co.uk/news/article...

"If you like a lot of chocolate (flavoured coating) on your biscuit join our Club"

05.02.2026 12:27 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

I agree - but there are many varieties of Timtam and some may be nicer than Penguins.

04.02.2026 17:36 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

I've finally taken advantage of one of the most significant benefits brought to us by Brexit.
I've bought a packer of TimTams from the local supermarket.

04.02.2026 14:59 πŸ‘ 3 πŸ” 0 πŸ’¬ 2 πŸ“Œ 0
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QUALIFY: The WHERE Condition for Analytic Functions Filtering analytic functions was not straight-forward in Oracle and most other databases. Oracle 26ai now supports the QUALIFY clause in SQL. It works like a WHERE condition, but can be used for an…

The QUALIFY clause enables you to filter rows using window functions

e.g. get the top ranked rows with

SELECT ... FROM ...
QUALIFY RANK () OVER ( ORDER BY ... ) = ...

@danischnider.bsky.social looks at how it works in Oracle AI Database 26ai

04.02.2026 12:01 πŸ‘ 0 πŸ” 2 πŸ’¬ 1 πŸ“Œ 0

Who was it who coined the term "syntactic icing"?

So Oracle transforms the QUALIFY query into the form you would otherwise have written.

Nothing wrong with the general strategy, it avoids the risk of programmer error, but it has "lost" optimisations occasionally where a manual rewrite doesn't.

04.02.2026 14:25 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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From magic to malware: How OpenClaw's agent skills become an attack surface | 1Password The same capabilities that make OpenClaw a groundbreaking tool also make it an urgent security risk. This blog contains confirmed examples of agent skills being used as malware vectors, and advice on ...

1Password not mincing words here:

"If you are experimenting with OpenClaw, do not do it on a company device. Full stop."

"If you have already run OpenClaw on a work device, treat it as a potential incident and engage your security team immediately."

1password.com/blog/from-ma...

03.02.2026 13:11 πŸ‘ 318 πŸ” 183 πŸ’¬ 5 πŸ“Œ 36

It often seems far more appropriate than the boring old "friend". (It also means I don't have to remember the order of the i and the e).

Is the vector thing a bitmap strategy?

03.02.2026 14:20 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

The next "big" question on the topic is whether the size of a set (for a list of set expressions) is (will be) going up from 1,000 to 4,000 to match the new limit on the number of columns in a table. (Asking for a fiend)
More seriously - how large was your session's PGA allocation with the 65,535?

03.02.2026 09:59 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Congrats to the winners in the Oracle Dev Gym championships!

1st Andrey Zaytsev
2nd mentzel.iudith
3rd whab@tele2.at

πŸ†πŸΎ

πŸ‘ to all competitors; we hope you enjoyed the challenge

Thanks to @kibeha.dk and @anthony-harper.bsky.social for writing & reviewing quizzes

blogs.oracle.com/sql/announci...

02.02.2026 16:19 πŸ‘ 5 πŸ” 2 πŸ’¬ 0 πŸ“Œ 0

Congratulations, and thanks for inviting me to speak at all those Trivadis Performance Days it was always a great pleasure to be part of that event.

All the best for pre-retirement, and for retirement when it finally comes.

31.01.2026 13:32 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0