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Improve documentation of random() function.

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Move random() and setseed() to a separate table, to have them grouped
together. Also add a notice that random() is not cryptographically secure.

Back-patch of commit 75fdcec145 into
all supported versions, per discussion of the need to document that
random() is just a wrapper around random(3).
This commit is contained in:
Tom Lane
2015-01-20 21:21:34 -05:00
parent 1681e2f740
commit b8e5f66991
1 changed files with 50 additions and 27 deletions
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77
doc/src/sgml/func.sgml
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@ -828,19 +828,6 @@
<entry><literal>0.785398163397448</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>random</primary>
</indexterm>
<literal><function>random()</function></literal>
</entry>
<entry><type>dp</type></entry>
<entry>random value in the range 0.0 &lt;= x &lt; 1.0</entry>
<entry><literal>random()</literal></entry>
<entry></entry>
</row>
<row>
<entry>
<indexterm>
@ -862,20 +849,6 @@
<entry><literal>42.44</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>setseed</primary>
</indexterm>
<literal><function>setseed(<type>dp</type>)</function></literal>
</entry>
<entry><type>void</type></entry>
<entry>set seed for subsequent <literal>random()</literal> calls (value between -1.0 and
1.0, inclusive)</entry>
<entry><literal>setseed(0.54823)</literal></entry>
<entry></entry>
</row>
<row>
<entry>
<indexterm>
@ -951,6 +924,56 @@
</tgroup>
</table>
<para>
<xref linkend="functions-math-random-table"> shows functions for
generating random numbers.
</para>
<table id="functions-math-random-table">
<title>Random Functions</title>
<tgroup cols="3">
<thead>
<row>
<entry>Function</entry>
<entry>Return Type</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>
<indexterm>
<primary>random</primary>
</indexterm>
<literal><function>random()</function></literal>
</entry>
<entry><type>dp</type></entry>
<entry>random value in the range 0.0 &lt;= x &lt; 1.0</entry>
</row>
<row>
<entry>
<indexterm>
<primary>setseed</primary>
</indexterm>
<literal><function>setseed(<type>dp</type>)</function></literal>
</entry>
<entry><type>void</type></entry>
<entry>set seed for subsequent <literal>random()</literal> calls (value between -1.0 and
1.0, inclusive)</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
The characteristics of the values returned by
<literal><function>random()</function></literal> depend
on the system implementation. It is not suitable for cryptographic
applications; see <xref linkend="pgcrypto"> module for an alternative.
</para>
<para>
Finally, <xref linkend="functions-math-trig-table"> shows the
available trigonometric functions. All trigonometric functions