Re: [HACKERS] Transform for pl/perl

2017-11-15 10:24 GMT+01:00 Oleg Bartunov <obartunov(at)gmail(dot)com>:

>
>
> On 14 Nov 2017 11:35, "Anthony Bykov" <a(dot)bykov(at)postgrespro(dot)ru> wrote:
>
> On Fri, 10 Nov 2017 14:40:21 +0100
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>
> > Hi
> >
> > 2017-10-24 14:27 GMT+02:00 Anthony Bykov <a(dot)bykov(at)postgrespro(dot)ru>:
> >
> > > There are some moments I should mention:
> > > 1. {"1":1}::jsonb is transformed into HV {"1"=>"1"}, while
> > > ["1","2"]::jsonb is transformed into AV ["1", "2"]
> > >
> > > 2. If there is a numeric value appear in jsonb, it will be
> > > transformed to SVnv through string (Numeric->String->SV->SVnv). Not
> > > the best solution, but as far as I understand this is usual
> > > practise in postgresql to serialize Numerics and de-serialize them.
> > >
> > > 3. SVnv is transformed into jsonb through string
> > > (SVnv->String->Numeric).
> > >
> > > An example may also be helpful to understand extension. So, as an
> > > example, function "test" transforms incoming jsonb into perl,
> > > transforms it back into jsonb and returns it.
> > >
> > > create extension jsonb_plperl cascade;
> > >
> > > create or replace function test(val jsonb)
> > > returns jsonb
> > > transform for type jsonb
> > > language plperl
> > > as $$
> > > return $_[0];
> > > $$;
> > >
> > > select test('{"1":1,"example": null}'::jsonb);
> > >
> > >
> > I am looking to this patch:
> >
> > 1. the patch contains some artefacts - look the word "hstore"
> >
> > 2. I got lot of warnings
> >
> >
> > make[1]: Vstupuje se do adresáře
> > „/home/pavel/src/postgresql/contrib/jsonb_plperl“
> > gcc -Wall -Wmissing-prototypes -Wpointer-arith
> > -Wdeclaration-after-statement -Wendif-labels
> > -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
> > -fwrapv -fexcess-precision=standard -g -ggdb -Og -g3
> > -fno-omit-frame-pointer -fPIC -I../../src/pl/plperl -I. -I.
> > -I../../src/include -D_GNU_SOURCE -I/usr/include/libxml2
> > -I/usr/lib64/perl5/CORE -c -o jsonb_plperl.o jsonb_plperl.c
> > jsonb_plperl.c: In function ‘SV_FromJsonbValue’: jsonb_plperl.c:83:9:
> > warning: ‘result’ may be used uninitialized in this function
> > [-Wmaybe-uninitialized] return (result);
> > ^
> > jsonb_plperl.c: In function ‘SV_FromJsonb’:
> > jsonb_plperl.c:95:10: warning: ‘object’ may be used uninitialized in
> > this function [-Wmaybe-uninitialized]
> > HV *object;
> > ^~~~~~
> > In file included from /usr/lib64/perl5/CORE/perl.h:5644:0,
> > from ../../src/pl/plperl/plperl.h:52,
> > from jsonb_plperl.c:17:
> > /usr/lib64/perl5/CORE/embed.h:404:19: warning: ‘value’ may be used
> > uninitialized in this function [-Wmaybe-uninitialized]
> > #define newRV(a) Perl_newRV(aTHX_ a)
> > ^~~~~~~~~~
> > jsonb_plperl.c:101:10: note: ‘value’ was declared here
> > SV *value;
> > ^~~~~
> > gcc -Wall -Wmissing-prototypes -Wpointer-arith
> > -Wdeclaration-after-statement -Wendif-labels
> > -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
> > -fwrapv -fexcess-precision=standard -g -ggdb -Og -g3
> > -fno-omit-frame-pointer -fPIC -shared -o jsonb_plperl.so
> > jsonb_plperl.o -L../../src/port -L../../src/common -Wl,--as-needed
> > -Wl,-rpath,'/usr/lib64/perl5/CORE',--enable-new-dtags -Wl,-z,relro
> > -specs=/usr/lib/rpm/redhat/redhat-hardened-ld
> > -fstack-protector-strong -L/usr/local/lib -L/usr/lib64/perl5/CORE
> > -lperl -lpthread -lresolv -lnsl -ldl -lm -lcrypt -lutil -lc make[1]:
> > Opouští se adresář „/home/pavel/src/postgresql/contrib/jsonb_plperl“
> >
> > [pavel(at)nemesis contrib]$ gcc --version
> > gcc (GCC) 7.2.1 20170915 (Red Hat 7.2.1-2)
> > Copyright (C) 2017 Free Software Foundation, Inc.
> > This is free software; see the source for copying conditions. There
> > is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
> > PARTICULAR PURPOSE.
> >
> > 3. regress tests passed
> >
> > 4. There are not any documentation - probably it should be part of
> > PLPerl
> >
> > 5. The regress tests doesn't coverage other datatypes than numbers. I
> > miss boolean, binary, object, ... Maybe using data::dumper or some
> > similar can be interesting
> >
> > Note - it is great extension, I am pleasured so transformations are
> > used.
> >
> > Regards
> >
> > Pavel
> > >
> > > --
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> > > To make changes to your subscription:
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> > >
>
> Hello,
> Thank you for your review. I have fixed most of your comments, except
> for the 5-th part, about data::dumper - I just couldn't understand
> your point, but I've added more tests with more complex objects if this
> helps.
>
> Please, take a look at new patch. You can find it in attachments to
> this message (it is called "0001-jsonb_plperl-extension-v2.patch")
>
>
> I'm curious, how much benefit we could get from this ? There are several
> publicly available json datasets, which can be used to measure performance
> gaining. I have bookmarks and review datasets available from
> http://www.sai.msu.su/~megera/postgres/files/, look at js.dump.gz and
> jr.dump.gz
>

I don't expect significant performance effect - it remove some
transformations - perl object -> json | json -> jsonb - but on modern cpu
these transformations should be fast. For me - main benefit is user comfort
- it does direct transformation from perl object -> jsonb

But some performance check can be interesting

Regards

Pavel

>
>
> --
> Anthony Bykov
> Postgres Professional: http://www.postgrespro.com
> The Russian Postgres Company
>
>
>