Jonathan Leto: June 2010 Archives

Rakudo Perl 6 in Your PostgreSQL Database!

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It has been a very exciting few weeks in the Perl 6 world with regard to database access. mberends++ just wrote a nice blog post about how Perl 6 support for DBI is ramping up with work on MiniDBI (formerly FakeDBI). Multiple developers recently made great progress on PostgreSQL drivers and have been improving the Parrot interface to libpq, Pg.pir .

I have also been dutifully hacking on PL/Perl6, which embeds Rakudo Perl 6 into your PostgreSQL datbase via PL/Parrot, and just recently merged the plperl6 branch, which adds the first basic support for PL/Perl 6. Here is how it currently works:

  • You must first install a recent version of Parrot and Rakudo Perl 6. I develop with Parrot trunk and Rakudo master because I often need very recent changes/bugfixes
  • You will need a moderately recent version of PostgreSQL. PL/Parrot has been known to work with versions as old as 8.3.8, but I mostly develop on the master branch, so 9.x will probably work best
  • When you type "make install" for Rakudo Perl 6, you will see that it installs a file called "perl6.pbc" into the lib/$version/languages/perl6 directory of the Parrot installation that Rakudo was configured with.

To tell PL/Parrot that you would also like PL/Perl6, you set the environment variable PERL6PBC to the full path of perl6.pbc like so:

export PERL6PBC=/Users/leto/git/rakudo/parrot_install/lib/2.5.0-devel/languages/perl6/perl6.pbc

A PBC file is Parrot bytecode, and the perl6.pbc file basically bundles all of Rakudo Perl 6 into a single file. You can play around with the Rakudo Perl 6 REPL by running:

$ parrot $PERL6PBC

which is pretty much the exact same thing as running the perl6 binary in your $PATH.

When you compile PL/Parrot with the $PERL6PBC environment variable set, it automatically creates a separate Parrot interpreter with the perl6.pbc bytecode loaded, so that Perl 6 code can be executed.

To run PL/Parrot tests, you type "make test". You can also do this the PostgreSQL way with "make installcheck", which will run the tests and verify that the output matches a certain, known output. "make tests" just generates the TAP output.

Currently PL/Perl 6 tests are not run by default, they have their own Makefile target: test_plperl6 This is what the output of "make test_plperl6" looks like currently, on commit 44a985f123 of the perl6_args branch.

We run a total of 9 tests, 6 of which correctly run Perl 6 code and pass. You will notice that all the failing tests are relating to passing arguments into Rakudo from PostgreSQL, which is what I am currently trying to get to work. Currently I am passing a Parrot ResizablePMCArray of the arguments to a Rakudo function and executing it, but the function can't seem to see it. My guess is that Rakudo wants native datatypes and not Parrot datatypes. If you know how to create Rakudo datatypes from PIR, please let me know :) I promise you will -Ofun.

What does PL/Perl 6 look like? Here is a nice example of a PL/Perl6 function which calculates the sum of all Fibonacci numbers <= 100:

CREATE FUNCTION test_fibonacci_plperl6(integer) RETURNS int LANGUAGE plperl6 AS $$
[+] (1, 1, *+* ... 100)
$$;

You will notice three spiffy new Perl 6 operators in there, the summation operator [+], the new range operator ... (which used to be .. in Perl 5), and the *+* operator. What exactly is the *+* operator? pmichaud++ jokingly referred to it as the "cheerleading plus", but it is actually just a plain old infix "+" operator, sandwiched by two "*" (a.k.a Whatever) operands. It basically takes the previous two elements in a list, sums them together and returns the sum, which is exactly how the Fibonacci sequence is defined.

If you are interested in hacking on PL/Perl 6, PL/Parrot or anything related, come join us in #plparrot on freenode, join the mailing list and fork us on github !

About this Archive

This page is a archive of recent entries written by Jonathan Leto in June 2010.

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