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plpgsql documentation

From: Chris Browne <cbbrowne(at)acm(dot)org>
To: pgsql-patches(at)postgresql(dot)org
Subject: plpgsql documentation
Date: 2006-05-25 22:39:15
Message-ID: 601wuh686k.fsf_-_@dba2.int.libertyrms.com (view raw or flat)
Thread:
Lists: pgsql-patches
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.

Index: plperl.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/plperl.sgml,v
retrieving revision 2.52
diff -c -u -r2.52 plperl.sgml
--- plperl.sgml	10 Mar 2006 19:10:48 -0000	2.52
+++ plperl.sgml	25 May 2006 22:38:45 -0000
@@ -17,6 +17,12 @@
    <ulink url="http://www.perl.com">Perl programming language</ulink>.
   </para>
 
+  <para> The usual advantage to using PL/Perl is that this allows use,
+   within stored functions, of the manyfold <quote>string
+    munging</quote> operators and functions available for Perl.  Parsing
+   complex strings may be be easier using Perl than it is with the
+   string functions and control structures provided in PL/pgsql.</para>
+  
   <para>
    To install PL/Perl in a particular database, use
    <literal>createlang plperl <replaceable>dbname</></literal>.
Index: plpgsql.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/plpgsql.sgml,v
retrieving revision 1.88
diff -c -u -r1.88 plpgsql.sgml
--- plpgsql.sgml	10 Mar 2006 19:10:48 -0000	1.88
+++ plpgsql.sgml	25 May 2006 22:38:46 -0000
@@ -155,21 +155,36 @@
 
     <para>
      That means that your client application must send each query to
-     the database server, wait for it to be processed, receive the
-     results, do some computation, then send other queries to the
-     server. All this incurs interprocess communication and may also
-     incur network overhead if your client is on a different machine
-     than the database server.
+     the database server, wait for it to be processed, receive and
+     process the results, do some computation, then send further
+     queries to the server.  All this incurs interprocess
+     communication and will also incur network overhead if your client
+     is on a different machine than the database server.
     </para>
 
     <para>
-     With <application>PL/pgSQL</application> you can group a block of computation and a
-     series of queries <emphasis>inside</emphasis> the
-     database server, thus having the power of a procedural
-     language and the ease of use of SQL, but saving lots of
-     time because you don't have the whole client/server
-     communication overhead. This can make for a
-     considerable performance increase.
+     With <application>PL/pgSQL</application> you can group a block of
+     computation and a series of queries <emphasis>inside</emphasis>
+     the database server, thus having the power of a procedural
+     language and the ease of use of SQL, but with considerable
+     savings because you don't have the whole client/server
+     communication overhead.
+    </para>
+    <itemizedlist>
+
+     <listitem><para> Elimination of additional round trips between
+     client and server </para></listitem>
+
+     <listitem><para> Intermediate results that the client does not
+     need do not need to be marshalled or transferred between server
+     and client </para></listitem>
+
+     <listitem><para> There is no need for additional rounds of query
+     parsing </para></listitem>
+
+    </itemizedlist>
+    <para> This can allow for a considerable performance increase as
+    compared to an application that does not use stored functions.
     </para>
 
     <para>
Index: pltcl.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/pltcl.sgml,v
retrieving revision 2.39
diff -c -u -r2.39 pltcl.sgml
--- pltcl.sgml	10 Mar 2006 19:10:48 -0000	2.39
+++ pltcl.sgml	25 May 2006 22:38:46 -0000
@@ -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>.

-- 
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