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sum() on int2 and int4 columns now uses an int8, not numeric, accumulator

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for speed reasons; its result type also changes to int8.  avg() on these
datatypes now accumulates the running sum in int8 for speed; but we still
deliver the final result as numeric, so that fractional accuracy is
preserved.

count() now counts and returns in int8, not int4.  I am a little nervous
about this possibly breaking users' code, but there didn't seem to be
a strong sentiment for avoiding the problem.  If we get complaints during
beta, we can change count back to int4 and add a "count8" aggregate.
For that matter, users can do it for themselves with a simple CREATE
AGGREGATE command; the int4inc function is still present, so no C hacking
is needed.

Also added max() and min() aggregates for OID that do proper unsigned
comparison, instead of piggybacking on int4 aggregates.

initdb forced.
This commit is contained in:
Tom Lane
2001-08-14 22:21:59 +00:00
parent 6f2943b52e
commit 5f7c2bdb53
13 changed files with 210 additions and 54 deletions
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16
doc/src/sgml/func.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.64 2001/07/11 22:14:01 momjian Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.65 2001/08/14 22:21:58 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -3768,7 +3768,7 @@ SELECT NULLIF(value, '(none)') ...
<row>
<entry>COUNT(*)</entry>
<entry>number of input values</entry>
<entry>The return value is of type <type>integer</type>.</entry>
<entry>The return value is of type <type>bigint</type>.</entry>
</row>
<row>
@ -3777,7 +3777,7 @@ SELECT NULLIF(value, '(none)') ...
Counts the input values for which the value of <replaceable
class="parameter">expression</replaceable> is not NULL.
</entry>
<entry></entry>
<entry>The return value is of type <type>bigint</type>.</entry>
</row>
<row>
@ -3822,7 +3822,9 @@ SELECT NULLIF(value, '(none)') ...
<type>smallint</type>, <type>integer</type>,
<type>bigint</type>, <type>real</type>, <type>double
precision</type>, <type>numeric</type>, <type>interval</type>.
The result is of type <type>numeric</type> for any integer type
The result is of type <type>bigint</type> for <type>smallint</type>
or <type>integer</type> input, <type>numeric</type> for
<type>bigint</type>
input, <type>double precision</type> for floating point input,
otherwise the same as the input data type.
</entry>
@ -3836,7 +3838,8 @@ SELECT NULLIF(value, '(none)') ...
<primary>variance</primary>
</indexterm>
The variance is the square of the standard deviation. The
supported data types are the same.
supported data types and result types are the same as for
standard deviation.
</entry>
</row>
@ -3848,7 +3851,8 @@ SELECT NULLIF(value, '(none)') ...
It should be noted that except for <function>COUNT</function>,
these functions return NULL when no rows are selected. In
particular, <function>SUM</function> of no rows returns NULL, not
zero as one might expect.
zero as one might expect. <function>COALESCE</function> may be
used to substitute zero for NULL when necessary.
</para>
</sect1>