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Update documentation to reflect the fact that ORDER BY, GROUP BY, etc

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are now driven by the default btree opclass, rather than assuming that
particular operator names have the needed semantics.
This commit is contained in:
Tom Lane
2003-08-17 22:09:00 +00:00
parent 1b68704482
commit 4215947986
4 changed files with 82 additions and 32 deletions
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12
doc/src/sgml/ref/create_operator.sgml
View File

@@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.35 2003/04/22 10:08:08 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.36 2003/08/17 22:09:00 tgl Exp $
PostgreSQL documentation
-->
@@ -43,17 +43,11 @@ CREATE OPERATOR <replaceable>name</replaceable> (
The operator name is a sequence of up to <symbol>NAMEDATALEN</>-1
(63 by default) characters from the following list:
<literallayout>
+ - * / &lt; &gt; = ~ ! @ # % ^ &amp; | ` ? $
+ - * / &lt; &gt; = ~ ! @ # % ^ &amp; | ` ?
</literallayout>
There are a few restrictions on your choice of name:
<itemizedlist>
<listitem>
<para>
<literal>$</literal> cannot be defined as a single-character operator,
although it can be part of a multicharacter operator name.
</para>
</listitem>
<listitem>
<para>
<literal>--</literal> and <literal>/*</literal> cannot appear anywhere in an operator name,
@@ -66,7 +60,7 @@ CREATE OPERATOR <replaceable>name</replaceable> (
<literal>-</literal>,
unless the name also contains at least one of these characters:
<literallayout>
~ ! @ # % ^ &amp; | ` ? $
~ ! @ # % ^ &amp; | ` ?
</literallayout>
For example, <literal>@-</literal> is an allowed operator name,
but <literal>*-</literal> is not.

26
doc/src/sgml/ref/select.sgml
View File

@@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.67 2003/05/04 02:23:16 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.68 2003/08/17 22:09:00 tgl Exp $
PostgreSQL documentation
-->
@@ -660,8 +660,11 @@ SELECT name FROM distributors ORDER BY code;
<literal>ORDER BY</> clause. If not specified, <literal>ASC</> is
assumed by default. Alternatively, a specific ordering operator
name may be specified in the <literal>USING</> clause.
<literal>ASC</> is equivalent to <literal>USING &lt;</> and
<literal>DESC</> is equivalent to <literal>USING &gt;</>.
<literal>ASC</> is usually equivalent to <literal>USING &lt;</> and
<literal>DESC</> is usually equivalent to <literal>USING &gt;</>.
(But the creator of a user-defined datatype can define exactly what the
default sort ordering is, and it might correspond to operators with other
names.)
</para>
<para>
@@ -671,7 +674,7 @@ SELECT name FROM distributors ORDER BY code;
</para>
<para>
Data of character types is sorted according to the locale-specific
Character-string data is sorted according to the locale-specific
collation order that was established when the database cluster
was initialized.
</para>
@@ -1003,7 +1006,9 @@ SELECT distributors.* FROM distributors d, distributors distributors;
that he will actually get. To help detect this sort of mistake,
PostgreSQL will warn if the implicit-<literal>FROM</literal>
feature is used in a <command>SELECT</command> statement that also
contains an explicit <literal>FROM</literal> clause.
contains an explicit <literal>FROM</literal> clause. Also, it is
possible to disable the implicit-<literal>FROM</literal> feature
by setting the <varname>ADD_MISSING_FROM</> parameter to false.
</para>
</refsect2>
@@ -1015,7 +1020,7 @@ SELECT distributors.* FROM distributors d, distributors distributors;
noise and can be omitted without affecting the meaning. The
<productname>PostgreSQL</productname> parser requires this key
word when renaming output columns because the type extensibility
features lead to parsing ambiguities in this context.
features lead to parsing ambiguities without it.
<literal>AS</literal> is optional in <literal>FROM</literal>
items, however.
</para>
@@ -1025,7 +1030,7 @@ SELECT distributors.* FROM distributors d, distributors distributors;
<title>Namespace Available to <literal>GROUP BY</literal> and <literal>ORDER BY</literal></title>
<para>
In the SQL standard, an <literal>ORDER BY</literal> clause may
In the SQL92 standard, an <literal>ORDER BY</literal> clause may
only use result column names or numbers, while a <literal>GROUP
BY</literal> clause may only use expressions based on input column
names. <productname>PostgreSQL</productname> extends each of
@@ -1036,6 +1041,13 @@ SELECT distributors.* FROM distributors d, distributors distributors;
expression will always be taken as input-column names, not as
result-column names.
</para>
<para>
SQL99 uses a slightly different definition which is not upward compatible
with SQL92. In most cases, however, <productname>PostgreSQL</productname>
will interpret an <literal>ORDER BY</literal> or <literal>GROUP
BY</literal> expression the same way SQL99 does.
</para>
</refsect2>
<refsect2>