http://qs1969.pair.com?node_id=11130406

tomgracey has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks

So this is basic question about Raku. I am experimenting with it whilst having not the slightest clue what I'm doing. Just the module/package/class (which is it anyway?) loading system seems rather baffling. But I digress.

So here's the problem:

I have a basic schema file, which looks like this: 

use Red;

model User {
    has Int $!id is serial;
    has Str $.username is column is rw;
    has Str $.password is column is rw;
    has @.vmails is relationship(*.user_id, :model<Vmail>);
}

model Vmail {
    has Int $!id is serial;
    has Int $!user_id is referencing(*.id, :model<User>);
    has Str $.name is column;
    has $.user is relationship(*.id, :model<User>);
}

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And my script looks like this: 
#!/usr/bin/raku

use Red;
use lib 'lib';
use Schema;

my $*RED-DB = database "Pg", :user<vmail_user>, :dbname<vmail>, :passw
+ord<--redacted-->;
my $user = User.^create( username => 'Bill' );
print "*** DONE ***\n";

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The database and tables exist in postgres (created manually rather than using Red) - and the table definitions are: 
 
# \d user
                          Table "public.user"
  Column  |  Type   |                     Modifiers
----------+---------+-------------------------------------------------
+--
 id       | integer | not null default nextval('user_id_seq'::regclass
+)
 username | text    |
 password | text    |
Indexes:
    "user_pkey" PRIMARY KEY, btree (id)
Referenced by:
    TABLE "vmail" CONSTRAINT "vmail_user_id_fkey" FOREIGN KEY (user_id
+) REFERENCES "user"(id)

=# \d vmail
                          Table "public.vmail"
 Column  |  Type   |                     Modifiers
---------+---------+--------------------------------------------------
+--
 id      | integer | not null default nextval('vmail_id_seq'::regclass
+)
 user_id | integer |
 name    | text    |
Indexes:
    "vmail_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
    "vmail_user_id_fkey" FOREIGN KEY (user_id) REFERENCES "user"(id)

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When I run the script I get the following output: 
Could not find Vmail in:
    file#/var/www/apps/raku/vmail/lib
    inst#/root/.raku
    inst#/opt/rakudo-pkg/share/perl6/site
    inst#/opt/rakudo-pkg/share/perl6/vendor
    inst#/opt/rakudo-pkg/share/perl6/core
    ap#
    nqp#
    perl5#
  in block  at /opt/rakudo-pkg/share/perl6/site/sources/9740DDE0E85E09
+3DCDF40F690C620BD9BAEE9078 (Red::Attr::Relationship) line 46
  in method relationship-model at /opt/rakudo-pkg/share/perl6/site/sou
+rces/9740DDE0E85E093DCDF40F690C620BD9BAEE9078 (Red::Attr::Relationshi
+p) line 43
  in method build-relationship at /opt/rakudo-pkg/share/perl6/site/sou
+rces/9740DDE0E85E093DCDF40F690C620BD9BAEE9078 (Red::Attr::Relationshi
+p) line 67
  in method <anon> at /opt/rakudo-pkg/share/perl6/site/sources/C6C0BDE
+B2D9A3E5141D8CD425806A5162AFE5DE9 (MetamodelX::Red::Relationship) lin
+e 58
  in method create at /opt/rakudo-pkg/share/perl6/site/sources/A963FC4
+C1C5D6923CAA0DC1451EE51EA254DA1ED (MetamodelX::Red::Model) line 483
  in block <unit> at test_red.raku line 9

[download]

Hm... I don't think I am such a huge fan of the SHA-1 hashes...

Any idea why it can't find Vmail? I thought it might be related to the order of declaration of the model statements. I note that one of the examples (here: https://github.com/FCO/Red/blob/master/examples/alive/Schema.rakumod) seems to declare empty(?) models first and redeclare them later (to avoid referencing a model the that doesn't exist? Seems a bit ugly). I don't know if this has anything to do with it, but I tried adding model Vmail{...} at the top with no effect on the output

I only ever ask dumb questions and don't expect this to be any different...! But any help for a raku first-timer would be much appreciated.

Thanks!

Replies are listed 'Best First'.
Re: [Raku] Trying to get Red see the schema
by smokemachine (Hermit) on Mar 28, 2021 at 14:29 UTC
    Hi! Sorry, I was too late to answer that on #raku. The problem here is that when you create a `:model<Something>` Red tries to `use` "Something", on that case `Vmail` but that file does not exist, to fix that you could simply add `:require<Schema>` on that. 
    use Red;

model User is table<_user> {
        has Int $!id is serial;
        has Str $.username is column is rw;
        has Str $.password is column{ :nullable } is rw;
        has @.vmails is relationship(*.user_id, :model<Vmail>, :requir
+e<Schema>);
}

model Vmail {
        has Int $!id is serial;
        has Int $!user_id is referencing(*.id, :model<User>, :require<
+Schema>);
        has Str $.name is column;
        has $.user is relationship(*.id, :model<User>, :require<Schema
+>);
}

    [download]
    I'm trying to make it not necessary.
[reply]
[d/l]

      Ah ok I see - thank you that is very helpful!

      I notice that you call your table _user (ie with an underscore). Is this because user is a reserved word in Postgres? Is there a way to actually have a table called user? I mean, in Postgres you would just have to make sure to double quote the word. Do you know if there's a way to switch on double quoting of table names?

[reply]
[d/l]
[select]
        I'm just finishing my last change to make it possible to use any table name. It's going to wrap the table name with "". I'll let you know when it's committed.
[reply]
Re: [Raku] Trying to get Red see the schema
by smokemachine (Hermit) on Mar 28, 2021 at 14:48 UTC
    It seems https://github.com/FCO/Red/blob/master/examples/alive/Schema.rakumod has the same problem as your code. I'll fix that example (that was written before `:api<2>`). About the: 
    model Log     {...}
model Person  {...}

    [download]
    That's the raku way to use a class/model before defining it, raku parses it in only 1 pass.
[reply]
[d/l]
Re: [Raku] Trying to get Red see the schema
by erix (Prior) on Mar 26, 2021 at 23:00 UTC

    Could it be a Vmail / vmail confusion?

    (because postgres will make all table/columns names lowercase, unless they are double-quoted)

    (just a guess - I know nothing about Raku)

[reply]

      Thanks for the suggestion. It could well be something like this. I am under the impression that when Red generates tables from schema files it converts names to lowercase, so I would assume it should pick up manually created ones just the same. Also from the output it does look like its missing a file rather than a db table. I could well be mistaken though!

[reply]
[d/l]
Re: [Raku] Trying to get Red see the schema
by perlfan (Vicar) on Mar 27, 2021 at 02:29 UTC
    I only ever ask dumb questions and don't expect this to be any different...! But any help for a raku first-timer would be much appreciated.

    You'd probably find a lot more help on the perl6/raku mailing list. No doubt some monks here can be helpful; but just so you don't waste too much time this is not the best place for these questions.
[reply]
      The question is only some hours old, and some monks are very much into Raku.

      So better don't call it off yet. ... :)

      > this is not the best place for these questions.

      I know you meant it in a helpful way. But saying something like this might set a tone. :)

      Raku questions are very much on topic and welcome here.

      Cheers Rolf
      (addicted to the Perl Programming Language :)
      Wikisyntax for the Monastery

[reply]
        yes, trying to be helpful and minimize wasted time; it'd actually be nice if there was some Raku section, yanno, for good will; for most it just looks like a crusty old perl 5 help site :) - I should note OP's use of [Raku] was nice and shows awareness. Can't count on most to be so courteous I'd think.
[reply]
[d/l]

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