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Default values for function arguments

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Pavel Stehule, with some tweaks by Peter Eisentraut
This commit is contained in:
Peter Eisentraut
2008-12-04 17:51:28 +00:00
parent 7b640b0345
commit 455dffbb73
29 changed files with 2848 additions and 2166 deletions
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20
doc/src/sgml/func.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.460 2008/11/14 00:51:46 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.461 2008/12/04 17:51:26 petere Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -11710,6 +11710,10 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
<primary>pg_get_function_arguments</primary>
</indexterm>
<indexterm>
<primary>pg_get_function_identity_arguments</primary>
</indexterm>
<indexterm>
<primary>pg_get_function_result</primary>
</indexterm>
@ -11799,7 +11803,12 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
<row>
<entry><literal><function>pg_get_function_arguments</function>(<parameter>func_oid</parameter>)</literal></entry>
<entry><type>text</type></entry>
<entry>get argument list for function</entry>
<entry>get argument list of function's definition (with default values)</entry>
</row>
<row>
<entry><literal><function>pg_get_function_identity_arguments</function>(<parameter>func_oid</parameter>)</literal></entry>
<entry><type>text</type></entry>
<entry>get argument list to identify a function (without argument names, default values)</entry>
</row>
<row>
<entry><literal><function>pg_get_function_result</function>(<parameter>func_oid</parameter>)</literal></entry>
@ -11920,7 +11929,12 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
of a function, in the form it would need to appear in within
<command>CREATE FUNCTION</>.
<function>pg_get_function_result</function> similarly returns the
appropriate <literal>RETURNS</> clause for the function.
appropriate <literal>RETURNS</> clause for the function.
<function>pg_get_function_identity_arguments</function> returns the
argument list necessary to identify a function, in the form it
would need to appear in within <command>ALTER FUNCTION</>, for
instance. This form omits default values and argument names, for
example.
</para>
<para>

26
doc/src/sgml/ref/create_function.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.81 2008/11/14 10:22:46 petere Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.82 2008/12/04 17:51:26 petere Exp $
-->
<refentry id="SQL-CREATEFUNCTION">
@ -21,7 +21,7 @@ $PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.81 2008/11/14 10:22
<refsynopsisdiv>
<synopsis>
CREATE [ OR REPLACE ] FUNCTION
<replaceable class="parameter">name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
<replaceable class="parameter">name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [ { DEFAULT | = } <replaceable class="parameter">defexpr</replaceable>] [, ...] ] )
[ RETURNS <replaceable class="parameter">rettype</replaceable>
| RETURNS TABLE ( <replaceable class="parameter">colname</replaceable> <replaceable class="parameter">coltype</replaceable> [, ...] ) ]
{ LANGUAGE <replaceable class="parameter">langname</replaceable>
@ -154,6 +154,20 @@ CREATE [ OR REPLACE ] FUNCTION
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">defexpr</replaceable></term>
<listitem>
<para>
An expression to be used as default value if the parameter is
not specified. The expression has to be convertable to the
argument type of the parameter. All parameters after a
parameter with default value have to be parameters with default
values as well.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">rettype</replaceable></term>
@ -667,6 +681,14 @@ COMMIT;
either before or after <replaceable class="parameter">argname</replaceable>.
But only the first way is standard-compliant.
</para>
<para>
The SQL standard does not specify parameter defaults. The syntax
with the <literal>DEFAULT</literal> key word is from Oracle, and it
is somewhat in the spirit of the standard: SQL/PSM uses it for
variable default values. The syntax with <literal>=</literal> is
used in T-SQL and Firebird.
</para>
</refsect1>

56
doc/src/sgml/xfunc.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.133 2008/10/31 19:37:56 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.134 2008/12/04 17:51:26 petere Exp $ -->
<sect1 id="xfunc">
<title>User-Defined Functions</title>
@ -663,6 +663,60 @@ SELECT mleast(VARIADIC ARRAY[10, -1, 5, 4.4]);
</para>
</sect2>
<sect2 id="xfunc-parameter-defaults">
<title><acronym>SQL</> Functions with Parameters Default Values</title>
<indexterm>
<primary>default values</primary>
</indexterm>
<para>
Functions can be declared with parameters with default values or
expressions. The default expressions are used as parameter value
if the parameter is not explicitly specified in a function call.
All parameters after a a parameter with default value have to be
parameters with default values as well.
</para>
<para>
For example:
<screen>
CREATE FUNCTION foo(a int DEFAULT 1, b int DEFAULT 2, c int DEFAULT 3)
RETURNS int
LANGUAGE SQL
AS $$
SELECT $1 + $2 + $3;
$$;
SELECT foo(10, 20, 30);
foo
-----
60
(1 row)
SELECT foo(10, 20);
foo
-----
33
(1 row)
SELECT foo(10);
foo
-----
15
(1 row)
SELECT foo();
foo
-----
6
(1 row)
</screen>
Instead of the key word <literal>DEFAULT</literal>,
the <literal>=</literal> sign can also be used.
</para>
</sect2>
<sect2 id="xfunc-sql-table-functions">
<title><acronym>SQL</acronym> Functions as Table Sources</title>