PL/Perl - New Features in PostgreSQL 9.0

PL/Perl New Featuresin PostgreSQL 9.0

Tim Bunce - June 2010

Creative Commons BY-NC-SA 3.0

PL/Perl Changes

‣ USER‣ INTERNAL‣ DBA‣ NYTPROF

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( "\\146\\157\\157") ==> "foo"

encode_bytea( "\x{263a}" ) ==> "\\xe298ba" UTF8 decode_bytea( "\\xe298ba" ) ==> "\342\230\272" 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 ) ==> undefencode_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 lateruse 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

PL/Perl Changes

‣ USER‣ INTERNAL‣ DBA‣ NYTPROF

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

PL/Perl Changes

‣ USER‣ INTERNAL‣ DBA‣ NYTPROF

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 configuationplperl.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!

PL/Perl Changes

‣ USER‣ INTERNAL‣ DBA‣ NYTPROF

Devel::NYTProfPerl 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.tvVideo: http://www.fosslc.org/drupal/content/plperl-new-features-90

Questions?

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