The Heap™ – Consultancy ©®

11:01 AM

A chairde - Morning all!

Morning

1:06 PM

Guys, I'm in a quandary - I've been on a bit of a benchmarking fetish recently - c.f. the long-running saga with Evan and myself. That aside for the moment (tests ongoing...), I answered a question this morning and used a REGEXP_REPLACE (PostgreSQL) to answer the question.

Being a curious chappie, I just took a quick look at how I'd solve this using non-regexp functionality. I did come up with a method, and it's as convoluted as many a regex. So, I decided to benchmark both solutions and to my astonishment, my convoluted solution is consistently 10% (1M runs of each, several times on db<>fiddle) faster than the simple regex one.

Now, I know that regexes are expensive, but I didn't expect this. I'm all the more surprised because I ran similar benchmarks 1M runs, here related to this question and the rexexp was <10% of the convoluted solution.

Just wondering if my benchmarking is off - is the code OK (think it is...) or are there any problems with what I've done? Any input/suggestions, URLs &c. welcome.

@Vérace-getVACCINATEDNOW what was the question that E sent you a C solution?

I think I tried something on some question but can't remember which one

@ypercubeᵀᴹ - it was this one. I've pretty much done with the benchmarking. Re. ping - yes, hit return key too soon!

Q: How can I calculate all grouping permutations of an input string in SQL?

did you try to send me half a ping? ;)

will you do on this one as well?

6

Given an input like "ABC" generate a query that calculates all potential splits of 0 or more of the given string, Desired output, A B C A BC AB C ABC Given an input like "ABCD" A B C D A BC D A B CD AB C D A BCD AB CD ABC D ABCD Not all that concerned with how ...

I think I have an improvement

Regex. Now you have two problems.

Jan 17 '20 at 12:56, by Tom V - Team Monica

regex sucks in any language

@PaulWhite I fail to understand these knee-jerk anti-regex reactions. They, like any other arrow in the programmer's quiver, have their place. Take a look at the code I had to resort to without REGEXP_REPLACE!

1:15 PM

Mar 13 '13 at 8:20, by Remus Rusanu

@ypercube the guy is already asking about WaitforMultipleObjects... Just add regex use for a perfect storm

SQL is like poetry - one is only limited by imagination!

May 6 at 19:04, by ypercubeᵀᴹ

@Vérace the regex in combination with a malformed post resulted in a 34 minute outage of SO

I could go on, but it was only a small joke

Things that are very powerful don't always perform well in simple cases

@Vérace-getVACCINATEDNOW they have their place, sure. In the never-use-this toolcase ;)

3

Dec 27 '20 at 11:14, by ypercubeᵀᴹ

regex is one of the things I avoid

Consistency!

@PaulWhite ha! nice one. almost identical to my recent comment

1:28 PM

@ypercubeᵀᴹ Take a look at the last two snippets here (30 lines of code becomes 3) - how much time does code spend in maintenance?

Unless you can improve my code?

@ypercubeᵀᴹ Is the improvement in yet? It already looks good! The word_permutations_yper(_word text) function snippet at the bottom of the community wiki is pretty good! We could add a GENERATE_SERIES(1, 1000...) to test?

Single runs aren't reliable!

@ypercubeᵀᴹ - any comments on my benchmarking here?

DMGregory

2:34 PM

Hi @Vérace-getVACCINATEDNOW - I got your flag, but I don't think there's an urgent need to purge any messages from the record. A follow-up message saying "Oops, that was incorrect" suffices, and avoids leaving a mysterious hole in the transcript.

@DMGregory - I actually made an error about making an error! :-) Brain fried today for some reason! Anyway, it's all good - the original actually stands! Thanks for your time and input!

DMGregory

Interesting!

flag? here?

Oh I see

2:56 PM

@Vérace-getVACCINATEDNOW Maybe your brain is using regexes today

3

@PaulWhite Excellent - 10/10! :-)