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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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8
doc/src/sgml/plperl.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.54 2006/05/29 13:51:23 adunstan Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.55 2006/05/30 11:40:21 momjian Exp $ -->
<chapter id="plperl">
<title>PL/Perl - Perl Procedural Language</title>
@ -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>.

41
doc/src/sgml/plpgsql.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.89 2006/05/28 03:03:17 adunstan Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.90 2006/05/30 11:40:21 momjian Exp $ -->
<chapter id="plpgsql">
<title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title>
@ -155,21 +155,36 @@ $$ LANGUAGE plpgsql;
<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>

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>.