postgresql/doc/src/sgml/ref/load.sgml

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$Header: /cvsroot/pgsql/doc/src/sgml/ref/load.sgml,v 1.7 1999/07/22 15:09:12 thomas Exp $
Postgres documentation
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<refentry id="SQL-LOAD">
 <refmeta>
  <refentrytitle id="SQL-LOAD-TITLE">
   LOAD
  </refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>
 <refnamediv>
  <refname>
   LOAD
  </refname>
  <refpurpose>
   Dynamically loads an object file
  </refpurpose>
 </refnamediv>
 <refsynopsisdiv>
  <refsynopsisdivinfo>
   <date>1999-07-20</date>
  </refsynopsisdivinfo>
  <synopsis>
LOAD '<replaceable class="PARAMETER">filename</replaceable>'
  </synopsis>

  <refsect2 id="R2-SQL-LOAD-1">
   <refsect2info>
    <date>1998-09-01</date>
   </refsect2info>
   <title>
    Inputs
   </title>
   <para>
    <variablelist>
     <varlistentry>
      <term><replaceable class="PARAMETER">filename</replaceable></term>
      <listitem>
       <para>
	Object file for dynamic loading.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>

  <refsect2 id="R2-SQL-LOAD-2">
   <refsect2info>
    <date>1998-09-24</date>
   </refsect2info>
   <title>
    Outputs
   </title>
   <para>

    <variablelist>
     <varlistentry>
      <term><computeroutput>
LOAD
       </computeroutput></term>
      <listitem>
       <para>
	Message returned on successful completion.
       </para>
      </listitem>
     </varlistentry>
     <varlistentry>
      <term><computeroutput>
ERROR:  LOAD: could not open file '<replaceable class="PARAMETER">filename</replaceable>'
       </computeroutput></term>
      <listitem>
       <para>
	Message returned if the specified file is not found. The file must be visible
	<emphasis>to the <productname>Postgres</productname> backend</emphasis>,
	with the appropriate full path name specified, to avoid this message.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>
 </refsynopsisdiv>

 <refsect1 id="R1-SQL-LOAD-1">
  <refsect1info>
   <date>1998-09-24</date>
  </refsect1info>
  <title>
   Description
  </title>

  <para>
   Loads an object (or ".o") file into the 
   <productname>Postgres</productname> backend address space.  Once a
   file is loaded, all functions in that file can be accessed.  This
   function is used in support of user-defined types and functions.
  </para>

  <para>
   If a file is not loaded using
   <command>LOAD</command>, 
   the file will be loaded automatically the first time the
   function is called by <productname>Postgres</productname>.
   <command>LOAD</command>
   can also be used to reload an object file if it has been edited and
   recompiled.  Only objects created from C language files are supported
   at this time.
  </para>

  <refsect2 id="R2-SQL-LOAD-3">
   <refsect2info>
    <date>1998-09-24</date>
   </refsect2info>
   <title>
    Notes
   </title>

   <para>
    Functions in loaded object files should not call functions in other
    object files loaded through the
    <command>LOAD</command>
    command. For example, all functions in file <literal>A</literal> should
    call each other, functions in the standard or math libraries, or in
    Postgres itself.  They should not call functions defined in a different
    loaded file <literal>B</literal>.
    This is because if <literal>B</literal> is reloaded, the Postgres loader is
    not able to relocate the calls from the functions in
    <literal>A</literal> into
    the new address space of <literal>B</literal>.
    If <literal>B</literal> is not reloaded, however, there will
    not be a problem.
   </para>
   <para>
    Object files must be compiled to contain position independent code.
    For example, 
    on DECstations you must use
    <application>/bin/cc</application>
    with the <literal>-G 0</literal> option when compiling object files to be
    loaded.
   </para>
   <para>
    Note that if you are porting <productname>Postgres</productname>
    to a new platform, <command>LOAD</command>
    will have to work in order to support ADTs.
   </para>
  </refsect2>
 </refsect1>

 <refsect1 id="R1-SQL-LOAD-2">
  <title>
   Usage
  </title>
  <para>
   Load the file <filename>/usr/postgres/demo/circle.o</filename>:

   <programlisting>
LOAD '/usr/postgres/demo/circle.o'
   </programlisting>
  </para>
 </refsect1>

 <refsect1 id="R1-SQL-LOAD-3">
  <title>
   Compatibility
  </title>

  <refsect2 id="R2-SQL-LOAD-4">
   <refsect2info>
    <date>1998-09-24</date>
   </refsect2info>
   <title>
    SQL92
   </title>
   <para>
    There is no <command>LOAD</command> in <acronym>SQL92</acronym>.
   </para>
  </refsect2>
 </refsect1>
</refentry>

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