Horton

Re: [PATCH] random_normal function

Paul Ramsey <pramsey@cleverelephant.ca>

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From: Paul Ramsey <pramsey@cleverelephant.ca>
To: Joe Conway <mail@joeconway.com>
Cc: Mark Dilger <mark.dilger@enterprisedb.com>, Pgsql Hackers <pgsql-hackers@postgresql.org>
Date: 2022-12-09T19:11:34Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Round off random_normal() test results one more decimal place.

  2. Remove pg_regress' never-documented "ignore" feature.

  3. Upgrade the random.sql regression test.

  4. Invent random_normal() to provide normally-distributed random numbers.


> On Dec 9, 2022, at 11:10 AM, Paul Ramsey <pramsey@cleverelephant.ca> wrote:
> 
> 
> 
>> On Dec 9, 2022, at 11:01 AM, Joe Conway <mail@joeconway.com> wrote:
>> 
>> On 12/9/22 13:51, Paul Ramsey wrote:
>>>> On Dec 9, 2022, at 10:39 AM, Mark Dilger <mark.dilger@enterprisedb.com> wrote:
>>>>> On Dec 8, 2022, at 1:53 PM, Paul Ramsey <pramsey@cleverelephant.ca> wrote:
>>>>> Just a utility function to generate random numbers from a normal
>>>>> distribution. I find myself doing this several times a year, and I am
>>>>> sure I must not be the only one.
>>>> Thanks for the patch.  What do you think about these results?
>>> Angels on pins time! :)
>> 
>> I just noticed this thread -- what is lacking in the normal_rand() function in the tablefunc contrib?
>> 
>> https://www.postgresql.org/docs/current/tablefunc.html#id-1.11.7.52.5
> 
> Simplicity I guess mostly. random_normal() has a direct analogue in random() which is also a core function. I mean it could equally be pointed out that a user can implement their own Box-Muller calculation pretty trivially. Part of this submission is a personal wondering to what extent the community values convenience vs composibility. The set-returning nature of normal_rand() may be a bit of a red herring to people who just want one value (even though normal_rand (1, 0.0, 1.0) does exactly what they want).

No related to the "reason to exist", but normal_rand() has some interesting behaviour under Mark's test cases!

select normal_rand (1, 'Inf', 'Inf'), a from generate_series(1,2) a;
 normal_rand | a 
-------------+---
         NaN | 1
    Infinity | 2
(2 rows)