DBIx::OO::Tree DBIx::OO::Tree is a Perl module to manipulate hierarchical data using the "nested sets" model.
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DBIx::OO::Tree Tags

Perl module data hierarchical hierarchical data nested sets

DBIx::OO::Tree Description

DBIx::OO::Tree is a Perl module to manipulate hierarchical data using the "nested sets" model. DBIx::OO::Tree is a Perl module to manipulate hierarchical data using the "nested sets" model.SYNOPSYS CREATE TABLE Categories ( id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY, label VARCHAR(255), -- these columns are required by DBIx::OO::Tree parent INTEGER UNSIGNED, lft INTEGER UNSIGNED NOT NULL, rgt INTEGER UNSIGNED NOT NULL, mvg TINYINT DEFAULT 0, INDEX(lft), INDEX(rgt), INDEX(mvg), INDEX(parent) ); * * * package Category; use base 'DBIx::OO'; use DBIx::OO::Tree; __PACKAGE__->table('Categories'); __PACKAGE__->columns(P => , E => ); # note it's not necessary to declare lft, rgt, mvg or parent. We # declare parent simply because it might be useful, but # DBIx::OO:Tree works with low-level SQL therefore it doesn't # require that the DBIx::OO object has these fields. # the code below creates the structure presented in my $electronics = Category->tree_append({ label => 'electronics' }); my $tvs = $electronics->tree_append({ label => 'televisions' }); my $tube = $tvs->tree_append({ label => 'tube' }); my $plasma = $tvs->tree_append({ label => 'plasma' }); my $lcd = $plasma->tree_insert_before({ label => 'lcd' }); my $portable = $tvs->tree_insert_after({ label => 'portable electronics' }); my $mp3 = $portable->tree_append({ label => 'mp3 players' }); my $flash = $mp3->tree_append({ label => 'flash' }); my $cds = $portable->tree_append({ label => 'cd players' }); my $radios = Category->tree_append($portable->id, { label => '2 way radios' }); # fetch and display a subtree my $data = $electronics->tree_get_subtree({ fields => }); my $levels = Category->tree_compute_levels($data); foreach my $i (@$data) { print ' ' x $levels->{$i->{id}}, $i->{label}, "n"; } ## or, create DBIx::OO objects from returned data: my $array = Category->init_from_data($data); print join("n", (map { ' ' x $levels->{$_->id} . $_->label } @$array)); # display path info my $data = $flash->tree_get_path; print join("n", (map { $_->{label} } @$data)); # move nodes around $mp3->tree_reparent($lcd->id); $tvs->tree_reparent($portable->id); $cds->tree_reparent(undef); $plasma->tree_move_before($tube->id); $portable->tree_move_before($electronics->id); # delete nodes $lcd->tree_delete;This module is a complement to DBIx::OO to facilitate storing trees in database using the "nested sets model", presented in . Its main ambition is to be extremely fast at retrieving data (sacrificing for this the performance of UPDATE-s, INSERT-s or DELETE-s). Currently this module requires you to have these columns in the table: - id: primary key (integer) - parent: integer, references the parent node (NULL for root nodes) - lft, rgt: store the node position - mvg: used only when moving nodes"parent" and "mvg" are not esentially required by the nested sets model as presented in , but they are necessary for this module to work. In particular, "mvg" is only required by functions that move nodes, such as tree_reparent(). If you don't want to move nodes around you can omit "mvg".Retrieval functions should be very fast (one SQL executed). To further promote speed, they don't return DBIx::OO blessed objects, but an array of hashes instead. It's easy to create DBIx::OO objects from these, if required, by calling DBIx::OO->init_from_data() (see DBIx::OO for more information).Insert/delete/move functions, however, need to ensure the tree integrity. Here's what happens currently: - tree_append, tree_insert_before, tree_insert_after -- these execute one SELECT and two UPDATE-s (that potentially could affect a lot of rows). - tree_delete: execute one SELECT, one DELETE and two UPDATE-s. - tree_reparent -- executes 2 SELECT-s and 7 UPDATE-s. I know, this sounds horrible--if you have better ideas I'd love to hear them. Requirements: · Perl

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