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-$Header: /cvsroot/pgsql/doc/src/sgml/plperl.sgml,v 2.5 2000/09/29 20:21:34 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/plperl.sgml,v 2.6 2000/12/19 18:16:25 petere Exp $
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- <chapter id="pl-perl">
- <title>PL/perl - Perl Procedural Language</title>
+<chapter id="plperl">
+ <title>PL/Perl - Perl Procedural Language</title>
+
+ <para>
+ PL/Perl allows you to write functions in the Perl programming
+ language which may be used in SQL queries as if they were built into
+ <productname>Postgres</productname>.
+ </para>
+
+ <para>
+ The PL/Perl intepreter is a full Perl interpreter. However, certain
+ operations have been disabled in order to maintain the security of
+ the system. In general, the operations that are restricted are
+ those that interact with the environment. This includes filehandle
+ operations, <literal>require</literal>, and <literal>use</literal>
+ (for external modules). It should be noted that this security is
+ not absolute. Indeed, several Denial-of-Service attacks are still
+ possible - memory exhaustion and endless loops are two examples.
+ </para>
+
+ <sect1 id="plperl-install">
+ <title>Building and Installing</title>
<para>
- This chapter describes how to compile, install and
- use PL/Perl.
+ In order to build and install PL/Perl if you are installing
+ <productname>Postgres</productname> from source then the
+ <option>--with-perl</option> must be supplied to the
+ <filename>configure</filename> script. PL/Perl requires that, when
+ <productname>Perl</productname> was installed, the
+ <filename>libperl</filename> library was build as a shared object.
+ At the time of this writing, this is almost never the case in the
+ Perl packages that are distributed with the operating systems. A
+ message like this will appear during the build to point out this
+ fact:
+<screen>
+<computeroutput>
+*****
+* Cannot build PL/Perl because libperl is not a shared library.
+* Skipped.
+*****
+</computeroutput>
+</screen>
+ Therefore it is likely that you will have to re-build and install
+ <productname>Perl</productname> manually to be able to build
+ PL/Perl.
</para>
- <sect1 id="plperl-overview">
- <title>Overview</title>
- <para>
- PL/Perl allows you to write functions in the Perl scripting
- language which may be used in SQL queries as if they were
- built into <productname>Postgres</productname>.
- </para>
- <para>
- The PL/Perl intepreter is a full Perl interpreter. However,
- certain operations have been disabled in order to increase
- the security level of the system.
- </para>
- <para>
- In general, the operations that are restricted are those that
- interact with the environment. This includes filehandle operations,
- <literal>require</literal>, and <literal>use</literal> (for external
- modules).
- </para>
- <para>
- It should be noted that this security is not absolute. Indeed, several
- Denial-of-Service attacks are still possible - memory exhaustion and
- endless loops are two.
- </para>
- </sect1>
- <sect1 id="plperl-install">
- <title>Building and Installing</title>
- <para>
- Assuming that the <productname>Postgres</productname>
- source tree is rooted at $PGSRC, then the Pl/perl source
- code is located in $PGSRC/src/pl/plperl.
- </para>
- <para>
- To build, simply do the following:
- <programlisting>
-cd $PGSRC/src/pl/plperl
-perl Makefile.PL
-make
- </programlisting>
- </para>
+ <para>
+ When you want to retry to build PL/Perl after having reinstalled
+ Perl, then change to the directory
+ <filename>src/pl/plperl</filename> in the
+ <productname>Postgres</productname> source tree and issue the commands
+<programlisting>
+gmake clean
+gmake all
+gmake install
+</programlisting>
+ </para>
- <para>
- This will create a shared library file. On a Linux system, it will be
- named plperl.so. The extension may differ on other systems.
- </para>
- <para>
- The shared library should then be copied into the lib subdirectory of the
- postgres installation.
- </para>
- <para>
- The createlang command is used to install the language into a database.
- If it is installed into template1, all future databases will have the
- language installed automatically.
- </para>
- </sect1>
+ <para>
+ The <command>createlang</command> command is used to install the
+ language into a database.
+<screen>
+<prompt>$</prompt> <userinput>createlang plperl template1</userinput>
+</screen>
+ If it is installed into template1, all future databases will have
+ the language installed automatically.
+ </para>
+ </sect1>
- <sect1 id="plperl-use">
- <title>Using PL/Perl</title>
- <para>
- Assume you have the following table:
- <programlisting>
+ <sect1 id="plperl-use">
+ <title>Using PL/Perl</title>
+
+ <para>
+ Assume you have the following table:
+<programlisting>
CREATE TABLE EMPLOYEE (
name text,
- basesalary int4,
- bonus int4 );
- </programlisting>
-
- In order to get the total compensation (base + bonus) we could
- define a function as follows:
- <programlisting>
-CREATE FUNCTION totalcomp(int4, int4) RETURNS int4
+ basesalary integer,
+ bonus integer
+);
+</programlisting>
+
+ In order to get the total compensation (base + bonus) we could
+ define a function as follows:
+<programlisting>
+CREATE FUNCTION totalcomp(integer, integer) RETURNS integer
AS 'return $_[0] + $_[1]'
LANGUAGE 'plperl';
- </programlisting>
+</programlisting>
- Note that the arguments are passed to the function in
- <literal>@_</literal> as might be expected. Also, because
- of the quoting rules for the SQL creating the function, you
- may find yourself using the extended quoting functions (qq[],
- q[], qw[]) more often that you are used to.
- </para>
- <para>
- We may now use our function like so:
- <programlisting>
-SELECT name, totalcomp(basesalary, bonus) from employee
- </programlisting>
- </para>
- <para>
- But, we can also pass entire tuples to our function:
- <programlisting>
-CREATE FUNCTION empcomp(employee) returns int4
- AS 'my $emp = shift;
- return $emp->{''basesalary''} + $emp->{''bonus''};'
- LANGUAGE 'plperl';
- </programlisting>
- A tuple is passed as a reference to hash. The keys are the names of
- fields in the tuples. The values are values of the corresponding
- field in the tuple.
- </para>
+ Notice that the arguments to the function are passed in
+ <varname>@_</varname> as might be expected.
+ </para>
+
+ <para>
+ We can now use our function like so:
+<programlisting>
+SELECT name, totalcomp(basesalary, bonus) FROM employee;
+</programlisting>
+ </para>
+
+ <para>
+ But, we can also pass entire tuples to our functions:
+<programlisting>
+CREATE FUNCTION empcomp(employee) RETURNS integer AS '
+ my $emp = shift;
+ return $emp->{''basesalary''} + $emp->{''bonus''};
+' LANGUAGE 'plperl';
+</programlisting>
+ A tuple is passed as a reference to a hash. The keys are the names
+ of the fields in the tuples. The hash values are values of the
+ corresponding fields in the tuple.
+ </para>
+
+ <tip>
<para>
- The new function <literal>empcomp</literal> can used like:
- <programlisting>
-SELECT name, empcomp(employee) from employee;
- </programlisting>
+ Because the function body is passed as an SQL string literal to
+ <command>CREATE FUNCTION</command> you have to escape single
+ quotes within your Perl source, either by doubling them as shown
+ above, or by using the extended quoting functions
+ (<literal>q[]</literal>, <literal>qq[]</literal>,
+ <literal>qw[]</literal>). Backslashes must be escaped by doubling
+ them.
</para>
- </sect1>
- </chapter>
+ </tip>
+
+ <para>
+ The new function <function>empcomp</function> can used like:
+<programlisting>
+SELECT name, empcomp(employee) FROM employee;
+</programlisting>
+ </para>
+
+ <para>
+ Here is an example of a function which will not work because file
+ system operations are not allowed for security reasons:
+<programlisting>
+CREATE FUNCTION badfunc() RETURNS integer AS '
+ open(TEMP, ">/tmp/badfile");
+ print TEMP "Gotcha!\n";
+ return 1;
+' LANGUAGE 'plperl';
+</programlisting>
+ The creation of the function will succeed, but executing it will not.
+ </para>
+
+ </sect1>
+</chapter>
<!-- Keep this comment at the end of the file
Local variables:
-README for PL/Perl 2000.10.24
-
-PREREQUISITES
-======================================================================
-+ Perl must be built as a shared library.
-+ when compiling Postgres, use the --with-perl option. Alternatively,
- you can build plperl separately in an already-configured source tree:
- cd to $POSTGRES_SRC/src/pl/plperl/ and do "gmake all install".
-
-CONFIGURING
-======================================================================
-+ as postgres super user:
- createlang plperl [database]
-
-NOTES ON USAGE
-======================================================================
-+ Use q[], qq[], and qw[] instead of single quotes in
- function definitions.
-+ When using escape sequences, you must backslash your
- backslashes, e.g.
- $alphanum =~ s/\W//g; # Wrong! Will replace capital W's
- $alphanum =~ s/\\W//g; # Right! Will replace non-word chars
-+ Arguments to the function are available in @_
-+ If argument is declared as a tuple, then tuple is represented as a
- hash reference.
-
-EXAMPLES
-======================================================================
-CREATE FUNCTION addints(int4, int4) RETURNS int4 AS '
-return $_[0] + $_[1]
-' LANGUAGE 'plperl';
-
-SELECT addints(3,4);
-
--- of course, you can pass tuples;
-CREATE TABLE twoints ( a integer, b integer);
-CREATE FUNCTION addtwoints(twoints) RETURNS integer AS '
-$tup = shift;
-return $tup->{"a"} + $tup->{"b"};
-' LANGUAGE 'plperl';
-
-SELECT addtwoints(twoints) from twoints;
-
--- here is one that will fail. Creating the function
--- will work, but using it will fail.
-CREATE FUNCTION badfunc() RETURNS int4 AS '
-open(TEMP, ">/tmp/badfile");
-print TEMP "Gotcha!\n";
-return 1;
-' LANGUAGE 'plperl';
-
-SELECT badfunc();
+PL/Perl allows you to write PostgreSQL functions and procedures in
+Perl. To include PL/Perl in the build use './configure --with-perl'.
+To build from this directory use 'gmake all; gmake install'. libperl
+must have been built as a shared library, which is usually not the
+case in standard installations.
+
+Consult the PostgreSQL User's Guide and the INSTALL file in the
+top-level directory of the source distribution for more information.
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