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Update PL documentation:

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An article at WebProNews quoted from the PG docs as to the merits of
stored procedures.  I have added a bit more material on their merits,
as well as making a few changes to improve the introductions to
PL/Perl and PL/Tcl.

Chris Browne
This commit is contained in:
Bruce Momjian
2006-05-30 11:40:21 +00:00
parent 4c494889a6
commit fcc02c20fc
3 changed files with 59 additions and 33 deletions
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43
doc/src/sgml/pltcl.sgml
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@@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.40 2006/05/27 20:24:16 adunstan Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.41 2006/05/30 11:40:21 momjian Exp $ -->
<chapter id="pltcl">
<title>PL/Tcl - Tcl Procedural Language</title>
@@ -25,22 +25,27 @@
<title>Overview</title>
<para>
PL/Tcl offers most of the capabilities a function
writer has in the C language, except for some restrictions.
PL/Tcl offers most of the capabilities a function writer has in
the C language, with a few restrictions, and with the addition of
the powerful string processing libraries that are available for
Tcl.
</para>
<para>
The good restriction is that everything is executed in a safe
Tcl interpreter. In addition to the limited command set of safe Tcl, only
a few commands are available to access the database via SPI and to raise
messages via <function>elog()</>. There is no way to access internals of the
database server or to gain OS-level access under the permissions of the
<productname>PostgreSQL</productname> server process, as a C function can do.
Thus, any unprivileged database user may be
permitted to use this language.
One compelling <emphasis>good</emphasis> restriction is that
everything is executed from within the safety of the context of a
Tcl interpreter. In addition to the limited command set of safe
Tcl, only a few commands are available to access the database via
SPI and to raise messages via <function>elog()</>. PL/Tcl
provides no way to access internals of the database server or to
gain OS-level access under the permissions of the
<productname>PostgreSQL</productname> server process, as a C
function can do. Thus, unprivileged database users may be trusted
to use this language; it does not give them unlimited authority.
</para>
<para>
The other, implementation restriction is that Tcl functions cannot
be used to create input/output functions for new data types.
The other notable implementation restriction is that Tcl functions
may not be used to create input/output functions for new data
types.
</para>
<para>
Sometimes it is desirable to write Tcl functions that are not restricted
@@ -55,12 +60,12 @@
a user logged in as the database administrator.
</para>
<para>
The shared object for the <application>PL/Tcl</> and <application>PL/TclU</> call handlers is
automatically built and installed in the
<productname>PostgreSQL</productname>
library directory if Tcl support is specified
in the configuration step of the installation procedure. To install
<application>PL/Tcl</> and/or <application>PL/TclU</> in a particular database, use the
The shared object code for the <application>PL/Tcl</> and
<application>PL/TclU</> call handlers is automatically built and
installed in the <productname>PostgreSQL</productname> library
directory if Tcl support is specified in the configuration step of
the installation procedure. To install <application>PL/Tcl</>
and/or <application>PL/TclU</> in a particular database, use the
<command>createlang</command> program, for example
<literal>createlang pltcl <replaceable>dbname</></literal> or
<literal>createlang pltclu <replaceable>dbname</></literal>.