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Implement 4 new aggregate functions from SQL2003. Specifically: var_pop(),

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var_samp(), stddev_pop(), and stddev_samp(). var_samp() and stddev_samp()
are just renamings of the historical Postgres aggregates variance() and
stddev() -- the latter names have been kept for backward compatibility.
This patch includes updates for the documentation and regression tests.
The catversion has been bumped.

NB: SQL2003 requires that DISTINCT not be specified for any of these
aggregates. Per discussion on -patches, I have NOT implemented this
restriction: if the user asks for stddev(DISTINCT x), presumably they
know what they are doing.
This commit is contained in:
Neil Conway
2006-03-10 20:15:28 +00:00
parent ab812ef326
commit 0ebf1cc834
9 changed files with 418 additions and 134 deletions
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83
doc/src/sgml/func.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.312 2006/03/10 19:10:47 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.313 2006/03/10 20:15:25 neilc Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -7914,6 +7914,46 @@ SELECT NULLIF(value, '(none)') ...
<type>double precision</type> for floating-point arguments,
otherwise <type>numeric</type>
</entry>
<entry>historical alias for <function>stddev_samp</function></entry>
</row>
<row>
<entry>
<indexterm>
<primary>standard deviation</primary>
<secondary>population</secondary>
</indexterm>
<function>stddev_pop(<replaceable class="parameter">expression</replaceable>)</function>
</entry>
<entry>
<type>smallint</type>, <type>int</type>,
<type>bigint</type>, <type>real</type>, <type>double
precision</type>, or <type>numeric</type>
</entry>
<entry>
<type>double precision</type> for floating-point arguments,
otherwise <type>numeric</type>
</entry>
<entry>population standard deviation of the input values</entry>
</row>
<row>
<entry>
<indexterm>
<primary>standard deviation</primary>
<secondary>sample</secondary>
</indexterm>
<function>stddev_samp(<replaceable class="parameter">expression</replaceable>)</function>
</entry>
<entry>
<type>smallint</type>, <type>int</type>,
<type>bigint</type>, <type>real</type>, <type>double
precision</type>, or <type>numeric</type>
</entry>
<entry>
<type>double precision</type> for floating-point arguments,
otherwise <type>numeric</type>
</entry>
<entry>sample standard deviation of the input values</entry>
</row>
@ -7951,9 +7991,48 @@ SELECT NULLIF(value, '(none)') ...
<type>double precision</type> for floating-point arguments,
otherwise <type>numeric</type>
</entry>
<entry>sample variance of the input values (square of the sample standard deviation)</entry>
<entry>historical alias for <function>var_samp</function></entry>
</row>
<row>
<entry>
<indexterm>
<primary>variance</primary>
<secondary>population</secondary>
</indexterm>
<function>var_pop</function>(<replaceable class="parameter">expression</replaceable>)
</entry>
<entry>
<type>smallint</type>, <type>int</type>,
<type>bigint</type>, <type>real</type>, <type>double
precision</type>, or <type>numeric</type>
</entry>
<entry>
<type>double precision</type> for floating-point arguments,
otherwise <type>numeric</type>
</entry>
<entry>population variance of the input values (square of the population standard deviation)</entry>
</row>
<row>
<entry>
<indexterm>
<primary>variance</primary>
<secondary>sample</secondary>
</indexterm>
<function>var_samp</function>(<replaceable class="parameter">expression</replaceable>)
</entry>
<entry>
<type>smallint</type>, <type>int</type>,
<type>bigint</type>, <type>real</type>, <type>double
precision</type>, or <type>numeric</type>
</entry>
<entry>
<type>double precision</type> for floating-point arguments,
otherwise <type>numeric</type>
</entry>
<entry>sample variance of the input values (square of the sample standard deviation)</entry>
</row>
</tbody>
</tgroup>
</table>