1#@!#!123s

��JFIF�� 1#@!#!123s
: / proc / self / root / usr / share / doc / postgresql-9.2.24 / html /
Filename : pltcl-unknown.html
back
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Modules and the unknown Command</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REV="MADE"
HREF="mailto:pgsql-docs@postgresql.org"><LINK
REL="HOME"
TITLE="PostgreSQL 9.2.24 Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="PL/Tcl - Tcl Procedural Language"
HREF="pltcl.html"><LINK
REL="PREVIOUS"
TITLE="Trigger Procedures in PL/Tcl"
HREF="pltcl-trigger.html"><LINK
REL="NEXT"
TITLE="Tcl Procedure Names"
HREF="pltcl-procnames.html"><LINK
REL="STYLESHEET"
TYPE="text/css"
HREF="stylesheet.css"><META
HTTP-EQUIV="Content-Type"
CONTENT="text/html; charset=ISO-8859-1"><META
NAME="creation"
CONTENT="2017-11-06T22:43:11"></HEAD
><BODY
CLASS="SECT1"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="5"
ALIGN="center"
VALIGN="bottom"
><A
HREF="index.html"
>PostgreSQL 9.2.24 Documentation</A
></TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
TITLE="Trigger Procedures in PL/Tcl"
HREF="pltcl-trigger.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="pltcl.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="60%"
ALIGN="center"
VALIGN="bottom"
>Chapter 40. PL/Tcl - Tcl Procedural Language</TD
><TD
WIDTH="20%"
ALIGN="right"
VALIGN="top"
><A
TITLE="Tcl Procedure Names"
HREF="pltcl-procnames.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="PLTCL-UNKNOWN"
>40.7. Modules and the <CODE
CLASS="FUNCTION"
>unknown</CODE
> Command</A
></H1
><P
>        PL/Tcl has support for autoloading Tcl code when used.
        It recognizes a special table, <TT
CLASS="LITERAL"
>pltcl_modules</TT
>, which
        is presumed to contain modules of Tcl code.  If this table
        exists, the module <TT
CLASS="LITERAL"
>unknown</TT
> is fetched from the table
        and loaded into the Tcl interpreter immediately before the first
        execution of a PL/Tcl function in a database session.  (This
        happens separately for each Tcl interpreter, if more than one is
        used in a session; see <A
HREF="pltcl-global.html"
>Section 40.4</A
>.)
       </P
><P
>        While the <TT
CLASS="LITERAL"
>unknown</TT
> module could actually contain any
        initialization script you need, it normally defines a Tcl
        <CODE
CLASS="FUNCTION"
>unknown</CODE
> procedure that is invoked whenever Tcl does
        not recognize an invoked procedure name.  <SPAN
CLASS="APPLICATION"
>PL/Tcl</SPAN
>'s standard version
        of this procedure tries to find a module in <TT
CLASS="LITERAL"
>pltcl_modules</TT
>
        that will define the required procedure.  If one is found, it is
        loaded into the interpreter, and then execution is allowed to
        proceed with the originally attempted procedure call.  A
        secondary table <TT
CLASS="LITERAL"
>pltcl_modfuncs</TT
> provides an index of
        which functions are defined by which modules, so that the lookup
        is reasonably quick.
       </P
><P
>        The <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> distribution includes
        support scripts to maintain these tables:
        <TT
CLASS="COMMAND"
>pltcl_loadmod</TT
>, <TT
CLASS="COMMAND"
>pltcl_listmod</TT
>,
        <TT
CLASS="COMMAND"
>pltcl_delmod</TT
>, as well as source for the standard
        <TT
CLASS="LITERAL"
>unknown</TT
> module in <TT
CLASS="FILENAME"
>share/unknown.pltcl</TT
>.  This module
        must be loaded
        into each database initially to support the autoloading mechanism.
       </P
><P
>        The tables <TT
CLASS="LITERAL"
>pltcl_modules</TT
> and <TT
CLASS="LITERAL"
>pltcl_modfuncs</TT
>
        must be readable by all, but it is wise to make them owned and
        writable only by the database administrator.  As a security
        precaution, PL/Tcl will ignore <TT
CLASS="LITERAL"
>pltcl_modules</TT
> (and thus,
        not attempt to load the <TT
CLASS="LITERAL"
>unknown</TT
> module) unless it is
        owned by a superuser.  But update privileges on this table can be
        granted to other users, if you trust them sufficiently.
       </P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="pltcl-trigger.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="pltcl-procnames.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Trigger Procedures in PL/Tcl</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="pltcl.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Tcl Procedure Names</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>