PL/Perl - New Features in PostgreSQL 9.0

PL/Perl New Features in PostgreSQL 9.0 Tim Bunce - June 2010 Creative Commons BY-NC-SA 3.0

PL/Perl Changes ‣ USER ‣ INTERNAL ‣ DBA ‣ NYTPROF

New Builtins

quote_... quote_literal( "foo" ) ==> "'foo'" quote_literal( "don't "carp"" ) ==> "'don''t "carp"'" quote_literal( "" ) ==> "''" quote_nullable( "foo" ) ==> "'foo'" quote_nullable( "don't "carp"" ) ==> "'don''t "carp"'" quote_nullable( "" ) ==> "''" quote_ident( "foo" ) ==> "foo" quote_ident( "don't "carp"" ) ==> ""don't ""carp"""" quote_ident( "" ) ==> """"

quote_...(undef) quote_literal( undef ) ==> undef quote_nullable( undef ) ==> "NULL" quote_ident( undef ) ==> """" (warn)

{en,de}code_bytea encode_bytea( "foo" ) ==> "x666f6f" decode_bytea( "x666f6f" ) ==> "foo" decode_bytea( "146157157") ==> "foo" encode_bytea( "x{263a}" ) ==> "xe298ba" UTF8 decode_bytea( "xe298ba" ) ==> "342230272" Not UTF8 encode_bytea( "" ) ==> "x" decode_bytea( "x" ) ==> "" decode_bytea( "" ) ==> "" encode_bytea( undef ) ==> "x" (warn) decode_bytea( undef ) ==> "" (warn)

looks_like_number looks_like_number( 1 ) ==> 1 looks_like_number( 0 ) ==> 1 looks_like_number( "+7.2e-9" ) ==> 1 looks_like_number( "foo" ) ==> 0 looks_like_number( "" ) ==> 0 looks_like_number( undef ) ==> undef looks_like_number( " 4 " ) ==> 1 looks_like_number( "5plus" ) ==> 0 (but '5plus'+0=5)

encode_array_* encode_array_literal( ["foo","bar"] ) ==> "{"foo", "bar"}" encode_array_constructor( ["foo","bar"] ) ==> "ARRAY['foo', 'bar']" encode_array_literal( [1,[2,[undef]]] ) ==> "{"1", {"2", {NULL}}}" encode_array_constructor( [1,[2,[undef]]] ) ==> "ARRAY['1', ARRAY['2', ARRAY[NULL]]]"

encode_array_* encode_array_literal( "foo" ) ==> "foo" encode_array_constructor( "foo" ) ==> "'foo'" encode_array_literal( undef ) ==> undef encode_array_constructor( undef ) ==> "NULL"

Trusted require/use • require/use work for already loaded modules use strict; # old way: BEGIN { strict->import(); } • extra pre-loaded modules use warnings; use Carp; use feature qw(say); # for perl 5.10 or later use utf8; # if server_encoding is utf8

CONTEXT: ... • PL/Perl tracks the context of log messages - before: WARNING: ...some warning from perl code... - now: WARNING: ...some warning from perl code... CONTEXT: PL/Perl function "..."

DO '...' LANGUAGE plperl; • Arbitrary chunks of perl code can be executed directly from psql, or client apps, via DO • No need to create and run a stored procedure each time. DO $$ spi_exec("... $_ ...") for 'a'..'z'; $$ language plperl;

Other Changes • Using $a and $b in sort blocks now works! • eval { ... } and eval "..." - can now be used in plperl • END blocks are now run at end of session - they can't (currently) access the database • Warnings from perl are now WARNINGs - they used to be NOTICE

INTERNAL • The Safe module is no longer used for plperl - Improved security and reduced call overheads - Upgrade to latest security patch! • Validates return values are in server encoding - ERROR: invalid byte sequence for encoding • Internal code refactoring and cleanup

New plperl.* Conﬁg • Specify perl code to run during initialization: plperl.on_init = '...perl...' plperl.on_plperlu_init = '...perl...' plperl.on_plperl_init = '...perl...' • Can only be set by superuser or postgres.conf • Code can't access the database

~ Timeline ~ ▾ Perl interpreter created on demand ▿ Options from PERL5OPT env var are processed ▿ PL/Perl support code bootstraps ▿ plperl.on_init code runs Above may happen in postmaster at startup if plperl is loaded via shared_preload_libraries ▾ Interpreter is specialised for plperl (or plperlu) ▿ Modules loaded: strict, warnings, features, Carp ▿ Perl operators are restricted (require, open etc.) ▿ DynaLoader package is deleted ▿ plperl.on_plperl_init code runs ▿ Database access is enabled

plperl.on_init • Handy to set global perl conﬁguation plperl.on_init='use lib qw(/myapp); use ...;' plperl.on_init='require "plperloninit.pl";' • SECURITY RISK! Only load modules you're happy for plperl code to use! Also check any other modules loaded as dependencies! Use Devel::TraceLoad to see what's actually loaded: PERL5OPT='-MDevel::Trace=summary' pg_ctl ...

PL/Perl Best Practice • Include explicit use statements in functions • Don't assume modules have been pre-loaded • For plperlu that'll actually load if needed • For plperl it'll check that module was loaded - so you'll get an immediate clear failure if not - for example on a replica with old postgres.conf ﬁle

plperl.on_plperl_init • Originally intended for things like - PGOPTIONS="-c plperl.on_plperl_init='...'" - to enable debug or proﬁling for a session • But... • Can only be set by superuser or postgres.conf - sadly, due to SECURITY DEFINER risks. - You shouldn't write SECURITY DEFINER functions in plperl if untrusted users can use plperl!

Devel::NYTProf Perl Source Code Proﬁler PostgreSQL::PLPerl::NYTProf

Enabling NYTProf • Via postgres.conf: plperl.on_init='use PostgreSQL::PLPerl::NYTProf' • Via environment variable: PERL5OPT='-MPostgreSQL::PLPerl::NYTProf' pg_ctl ... • Immediately active. To enable on demand: NYTPROF=start=no PERL5OPT=... pg_ctl ... DO 'DB::enable_profile' LANGUAGE plperl;

Reporting from NYTProf • Writes per-backend data ﬁles: $PGDATA/nytprof.out.$pid • To generate a report: nytprofhtml --file=$PGDATA/nytprof.out.4321 --open

~ Demo ~ Screencast: http://timbunce.blip.tv Video: http://www.fosslc.org/drupal/content/plperl-new-features-90

Questions? Tim.Bunce@pobox.com http://blog.timbunce.org @timbunce on twitter

http://xkcd.com/519/

PL/Perl - New Features in PostgreSQL 9.0

by Tim Bunce on May 30, 2010

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