From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 23 Jul 2022 23:00:30 +0000 (-0400)
Subject: Doc: improve documentation about random().
X-Git-Tag: REL_12_12~24
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=042554d55d8539ea621ecf25d10d8c38ff1a2324;p=thirdparty%2Fpostgresql.git

Doc: improve documentation about random().

We didn't explicitly say that random() uses a randomly-chosen seed
if you haven't called setseed().  Do so.

Also, remove ref/set.sgml's no-longer-accurate (and never very
relevant) statement that the seed value is multiplied by 2^31-1.

Back-patch to v12 where set.sgml's claim stopped being true.
The claim that we use a source of random bits as seed was debatable
before 4203842a1, too, so v12 seems like a good place to stop.

Per question from Carl Sopchak.

Discussion: https://postgr.es/m/f37bb937-9d99-08f0-4de7-80c91a3cfc2e@sopchak.me
---

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 8b4283e3cc4..44cc4875323 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1171,6 +1171,9 @@
    subsequent <function>random()</function> calls in the current session are
    repeatable by re-issuing <function>setseed()</function> with the same
    argument.
+   Without any prior <function>setseed()</function> call in the same
+   session, the first <function>random()</function> call obtains a seed
+   from a platform-dependent source of random bits.
   </para>
 
   <para>
diff --git a/doc/src/sgml/ref/set.sgml b/doc/src/sgml/ref/set.sgml
index 63f312e812a..22d0e3f6e49 100644
--- a/doc/src/sgml/ref/set.sgml
+++ b/doc/src/sgml/ref/set.sgml
@@ -175,8 +175,7 @@ SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="parameter">timezone</rep
       <para>
        Sets the internal seed for the random number generator (the
        function <function>random</function>).  Allowed values are
-       floating-point numbers between -1 and 1, which are then
-       multiplied by 2<superscript>31</superscript>-1.
+       floating-point numbers between -1 and 1 inclusive.
       </para>
 
       <para>