Problem with Mojo::Pg

[Alexey Stavrov]

I have this code which not output "666", "End Inserts", "End". What i do wrong?

#!/usr/bin/perl


use strict;
use warnings;
use v5.10;


use Mojo::Pg;
use Mojo::IOLoop;


my $pg = Mojo::Pg->new('postgresql://alex@/test');


my $db = $pg->db;


$db->query(q{create table if not exists qwe (num integer, text text)});


sub upsert {
  Mojo::IOLoop->delay(
    sub {
      my $delay = shift;
      for my $i (1 .. 30) {
        warn "update: $i";
        $db->query(q{update qwe set num = ? where text = ?}, $i, "$i" => $delay->begin);
      }
    },
    sub {
      my $delay = shift;


      $delay->pass;


      for my $i (1 .. 30) {
        my ($err, $res) = (shift, shift);
        unless ($res->rows) {
          my $end = $delay->begin;
          say "insert $i";
          $db->query(q{insert into qwe(num, text) values (?, ?)}, $i, "$i" => sub { say '666'; $end->(@_); });
        }
      }
    },
    sub {
      say 'End inserts';
      Mojo::IOLoop->stop;
    }
  );
}


upsert();


Mojo::IOLoop->start;


say 'End';

Thanks.

[Daniel Mantovani]

In Mojo::IOLoop either $delay->begin or $delay->end must be invoked BEFORE you leave each step. It doesn't seem to be the case in the first step.

There is a very nice explanation of what is hapening here: http://www.slideshare.net/deepfountainconsulting/asynchronous-programming-patterns-in-perl. There is even a very similar case in the quiz # 1, page 91. Just writing $delay->begin inside a callback does not mean you are actually invoking it before you leave the step.

Second step looks fine, I tried but couldn't actually make it work :( but hope this comment will help.

BR,

Daniel

[Dan Book]

That is not correct. The callback from $delay->begin is intended to be invoked when the non-blocking activity is ready, after the control has returned to the event loop.

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[Alexey Stavrov]

You are wrong. First callback is correct and second callback is called.

If "$db" replace on "$pg->db" then it works fine, but i don't know why this example not work.

вторник, 24 марта 2015 г., 18:57:49 UTC+5 пользователь Daniel Mantovani написал:

[Dotan Dimet]

There's a $delay->pass at the 2nd line of the 2nd step, which I think will cause it to skip right down to the 3rd step?

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[Alexey Stavrov]

Yes, you right. May be need to do truncate table qwe at least and delete "$delay->pass;" line to reduce number of lines in main logic.

вторник, 24 марта 2015 г., 19:52:13 UTC+5 пользователь Dotan Dimet написал: