From 4c9e5162f56d2e9d8e690000a046ff4f59e2268d Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 23 Jul 2022 19:00:30 -0400
Subject: [PATCH] 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
---
 doc/src/sgml/func.sgml    | 3 +++
 doc/src/sgml/ref/set.sgml | 3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 560b6d7d33..53ab19732c 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1889,6 +1889,9 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
    subsequent <function>random()</function> calls in the current session
    can be repeated 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 339ee9eec9..c4aab56a2d 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>