[Dbix-class] Setup relationship for 'modified preorder tree traversal' structure

[Wade.Stuart at fallon.com]

Take a look at MojoMojo -- it has a pretty complete NS Tree implementation
(modified preorder tree traversal ~ NS Tree  or so it looks so via the code
below).




Charlie Garrison <garrison at zeta.org.au> wrote on 06/24/2007 02:59:29 PM:

> Good morning,
>
> I am using 'modified preorder tree traversal' for one of my
> tables and I'm having trouble working out how to create the
> relationship for descendant records.
>
> The table looks like (simplified):
>
> CREATE TABLE access_tree (
>    atr_key int(10) unsigned NOT NULL auto_increment,
>    participant_key int(10) unsigned DEFAULT '0' NOT NULL,
>    lft bigint(21) unsigned DEFAULT '0' NOT NULL,
>    rgt bigint(21) unsigned DEFAULT '0' NOT NULL,
>    PRIMARY KEY (atr_key),
>    KEY participant_key (participant_key),
>    KEY lft (lft),
>    KEY rgt (rgt)
> );
>
> My model looks like this (simplified):
>
> package RPDB::AccessTree;
>
> use base 'DBIx::Class';
> use strict;
> use warnings;
>
> __PACKAGE__->load_components(qw/ Core /);
> __PACKAGE__->table('access_tree');
> __PACKAGE__->add_columns(qw/ atr_key participant_key lft rgt /);
> __PACKAGE__->set_primary_key('atr_key');
>
> __PACKAGE__->belongs_to(user => 'RPDB::User', 'atr_key'); #
> reverse rel setup in RPDB::User
> __PACKAGE__->belongs_to(participant => 'RPDB::Participant',
> 'participant_key');
> __PACKAGE__->has_many(descendants => 'RPDB::AccessTree',
>      { 'foreign.lft' => { -between => [ 'self.lft', 'self.rgt' ]
> } },
>      { cascade_delete => 0 }
> );
>
> And I am using the relationship in my controller:
>
> my $descendants = $c->user->atr->descendants;
>
> Which generates an error like:
>
> "DBIx::Class::Relationship::Accessor::__ANON__(): Invalid rel
> cond val HASH(0x1e31984)
>
> I haven't been able to find examples of more complex join
> criteria; I ended up with the above following the manual...
>
>  From DBIC::Relationship::Base:
> The condition needs to be an SQL::Abstract-style representation
> of the join between the tables.
>
>  From SQL::Abstract:
> You can use this same format to use other grouping functions,
> such as BETWEEN, SOME, and so forth. For example:
>      my %where  = (
>          user   => 'nwiger',
>          completion_date => {
>             -not_between => ['2002-10-01', '2003-02-06']
>          }
>      );
>
> If anyone can show me where I'm going wrong and how I should
> create the join criteria (or some other way of approaching
> this), then I would appreciate it.
>
> Thanks,
> Charlie
>
> --
>     Charlie Garrison  <garrison at zeta.org.au>
>     PO Box 141, Windsor, NSW 2756, Australia
>
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