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Complete merge of all old man page information.
ecpg reference page still needs formatting.
This commit is contained in:
Thomas G. Lockhart
@ -1,6 +1,11 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_function.sgml,v 1.9 1999/07/22 15:09:07 thomas Exp $
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Postgres documentation
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-->
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<refentry id="SQL-CREATEFUNCTION">
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<refmeta>
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<refentrytitle>
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<refentrytitle id="sql-createfunction-title">
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CREATE FUNCTION
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</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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@ -15,7 +20,7 @@
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</refnamediv>
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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<date>1998-09-09</date>
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<date>1999-07-20</date>
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</refsynopsisdivinfo>
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<synopsis>
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CREATE FUNCTION <replaceable class="parameter">name</replaceable> ( [ <replaceable class="parameter">ftype</replaceable> [, ...] ] )
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@ -47,6 +52,10 @@ CREATE FUNCTION <replaceable class="parameter">name</replaceable> ( [ <replaceab
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<listitem>
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<para>
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The data type of function arguments.
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The input types may be base or complex types, or
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<firstterm>opaque</firstterm>.
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<literal>opaque</literal> indicates that the function
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accepts arguments of an invalid type such as <type>char *</type>.
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</para>
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</listitem>
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</varlistentry>
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@ -55,6 +64,12 @@ CREATE FUNCTION <replaceable class="parameter">name</replaceable> ( [ <replaceab
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<listitem>
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<para>
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The return data type.
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The output type may be specified as a base type, complex type,
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<literal>setof <replaceable class="parameter">type</replaceable></literal>,
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or <literal>opaque</literal>.
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The <literal>setof</literal>
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modifier indicates that the function will return a set of items,
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rather than a single item.
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</para>
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</listitem>
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</varlistentry>
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@ -77,7 +92,9 @@ CREATE FUNCTION <replaceable class="parameter">name</replaceable> ( [ <replaceab
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or '<replaceable class="parameter">plname</replaceable>',
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where '<replaceable class="parameter">plname</replaceable>'
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is the name of a created procedural
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language. See <command>CREATE LANGUAGE</command> for details.
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language. See
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<xref linkend="sql-createlanguage-title" endterm="sql-createlanguage-title">
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for details.
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</para>
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</listitem>
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</varlistentry>
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@ -133,43 +150,52 @@ CREATE
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Notes
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</title>
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<para>
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Refer to the chapter on functions
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in the <citetitle>PostgreSQL Programmer's Guide</citetitle>
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for further information.
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Refer to the chapter in
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the <citetitle>PostgreSQL Programmer's Guide</citetitle>
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on extending
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<productname>Postgres</productname> via functions
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for further information on writing external functions.
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</para>
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<para>
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Use <command>DROP FUNCTION</command>
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to drop user-defined functions.
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</para>
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<para>
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<productname>Postgres</productname> allows function "overloading";
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that is, the same name can be used for several different functions
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so long as they have distinct argument types. This facility must be
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used with caution for INTERNAL and C-language functions, however.
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</para>
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<para>
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<productname>Postgres</productname> allows function "overloading";
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that is, the same name can be used for several different functions
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so long as they have distinct argument types. This facility must be
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used with caution for <literal>internal</literal>
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and C-language functions, however.
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</para>
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<para>
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Two INTERNAL functions cannot have the same C name without causing
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errors at link time. To get around that, give them different C names
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(for example, use the argument types as part of the C names), then
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specify those names in the AS clause of <command>CREATE FUNCTION</command>.
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If the AS clause is left empty then <command>CREATE FUNCTION</command>
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assumes the C name of the function is the same as the SQL name.
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</para>
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<para>
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Two <literal>internal</literal>
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functions cannot have the same C name without causing
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errors at link time. To get around that, give them different C names
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(for example, use the argument types as part of the C names), then
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specify those names in the AS clause of <command>CREATE FUNCTION</command>.
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If the AS clause is left empty then <command>CREATE FUNCTION</command>
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assumes the C name of the function is the same as the SQL name.
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</para>
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<para>
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For dynamically-loaded C functions, the SQL name of the function must
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be the same as the C function name, because the AS clause is used to
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give the path name of the object file containing the C code. In this
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situation it is best not to try to overload SQL function names. It
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might work to load a C function that has the same C name as an internal
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function or another dynamically-loaded function --- or it might not.
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On some platforms the dynamic loader may botch the load in interesting
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ways if there is a conflict of C function names. So, even if it works
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for you today, you might regret overloading names later when you try
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to run the code somewhere else.
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</para>
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<para>
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For dynamically-loaded C functions, the SQL name of the function must
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be the same as the C function name, because the AS clause is used to
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give the path name of the object file containing the C code. In this
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situation it is best not to try to overload SQL function names. It
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might work to load a C function that has the same C name as an internal
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function or another dynamically-loaded function --- or it might not.
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On some platforms the dynamic loader may botch the load in interesting
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ways if there is a conflict of C function names. So, even if it works
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for you today, you might regret overloading names later when you try
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to run the code somewhere else.
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</para>
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<para>
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A C function cannot return a set of values.
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</para>
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</refsect2>
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</refsect1>
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@ -195,7 +221,7 @@ SELECT one() AS answer;
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</para>
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<para>
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To create a C function, calling a routine from a user-created
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This example creates a C function by calling a routine from a user-created
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shared library. This particular routine calculates a check
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digit and returns TRUE if the check digit in the function parameters
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is correct. It is intended for use in a CHECK contraint.
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@ -216,25 +242,26 @@ CREATE TABLE product (
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</programlisting>
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</refsect1>
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<refsect1 id="R1-SQL-CREATEFUNCTION-3">
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<title>
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Bugs
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</title>
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<para>
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A C function cannot return a set of values.
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-CREATEFUNCTION-4">
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<title>
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Compatibility
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</title>
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<para>
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<command>CREATE FUNCTION</command> is
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a <productname>Postgres</productname> language extension.
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</para>
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<refsect2 id="R2-SQL-CREATEFUNCTION-4">
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<refsect2info>
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<date>1998-04-15</date>
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</refsect2info>
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<title>
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SQL92
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</title>
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<para>
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<command>CREATE FUNCTION</command> is
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a <productname>Postgres</productname> language extension.
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</para>
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</refsect2>
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<refsect2 id="R2-SQL-CREATEFUNCTION-5">
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<refsect2info>
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<date>1998-09-09</date>
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</refsect2info>
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