Horton

Re: [PATCH] random_normal function

Mark Dilger <mark.dilger@enterprisedb.com>

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From: Mark Dilger <mark.dilger@enterprisedb.com>
To: Paul Ramsey <pramsey@cleverelephant.ca>
Cc: Pgsql Hackers <pgsql-hackers@postgresql.org>
Date: 2022-12-09T18:39:22Z
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 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?

+-- The semantics of a negative stddev are not well defined
+SELECT random_normal(mean := 0, stddev := -1);
+    random_normal    
+---------------------
+ -1.0285744583010896
+(1 row)
+
+SELECT random_normal(mean := 0, stddev := '-Inf');
+ random_normal 
+---------------
+      Infinity
+(1 row)
+
+-- This result may be defensible...
+SELECT random_normal(mean := '-Inf', stddev := 'Inf');
+ random_normal 
+---------------
+     -Infinity
+(1 row)
+
+-- but if so, why is this NaN?
+SELECT random_normal(mean := 'Inf', stddev := 'Inf');
+ random_normal 
+---------------
+           NaN
+(1 row)
+

—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
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