database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-13 07:41:39 +03:00
Code Activity

Add functions to generate random numbers in a specified range.

Browse Source 
This adds 3 new variants of the random() function:

    random(min integer, max integer) returns integer
    random(min bigint, max bigint) returns bigint
    random(min numeric, max numeric) returns numeric

Each returns a random number x in the range min <= x <= max.

For the numeric function, the number of digits after the decimal point
is equal to the number of digits that "min" or "max" has after the
decimal point, whichever has more.

The main entry points for these functions are in a new C source file.
The existing random(), random_normal(), and setseed() functions are
moved there too, so that they can all share the same PRNG state, which
is kept private to that file.

Dean Rasheed, reviewed by Jian He, David Zhang, Aleksander Alekseev,
and Tomas Vondra.

Discussion: https://postgr.es/m/CAEZATCV89Vxuq93xQdmc0t-0Y2zeeNQTdsjbmV7dyFBPykbV4Q@mail.gmail.com
This commit is contained in:
Dean Rasheed
2024-03-27 10:12:39 +00:00
parent 818861eb57
commit e6341323a8
13 changed files with 1022 additions and 101 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
doc/src/sgml/func.sgml
View File

@ -1862,6 +1862,39 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>random</primary>
</indexterm>
<function>random</function> ( <parameter>min</parameter> <type>integer</type>, <parameter>max</parameter> <type>integer</type> )
<returnvalue>integer</returnvalue>
</para>
<para role="func_signature">
<function>random</function> ( <parameter>min</parameter> <type>bigint</type>, <parameter>max</parameter> <type>bigint</type> )
<returnvalue>bigint</returnvalue>
</para>
<para role="func_signature">
<function>random</function> ( <parameter>min</parameter> <type>numeric</type>, <parameter>max</parameter> <type>numeric</type> )
<returnvalue>numeric</returnvalue>
</para>
<para>
Returns a random value in the range
<parameter>min</parameter> &lt;= x &lt;= <parameter>max</parameter>.
For type <type>numeric</type>, the result will have the same number of
fractional decimal digits as <parameter>min</parameter> or
<parameter>max</parameter>, whichever has more.
</para>
<para>
<literal>random(1, 10)</literal>
<returnvalue>7</returnvalue>
</para>
<para>
<literal>random(-0.499, 0.499)</literal>
<returnvalue>0.347</returnvalue>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
@ -1906,19 +1939,19 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in
</table>
<para>
The <function>random()</function> function uses a deterministic
pseudo-random number generator.
The <function>random()</function> and <function>random_normal()</function>
functions listed in <xref linkend="functions-math-random-table"/> use a
deterministic pseudo-random number generator.
It is fast but not suitable for cryptographic
applications; see the <xref linkend="pgcrypto"/> module for a more
secure alternative.
If <function>setseed()</function> is called, the series of results of
subsequent <function>random()</function> calls in the current session
subsequent calls to these functions 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
session, the first call to any of these functions obtains a seed
from a platform-dependent source of random bits.
These remarks hold equally for <function>random_normal()</function>.
</para>
<para>