This is a Laravel 4-10 package for working with trees in relational databases.
Contents:
Nested sets or Nested Set Model is a way to effectively store hierarchical data in a relational table. From wikipedia:
The nested set model is to number the nodes according to a tree traversal, which visits each node twice, assigning numbers in the order of visiting, and at both visits. This leaves two numbers for each node, which are stored as two attributes. Querying becomes inexpensive: hierarchy membership can be tested by comparing these numbers. Updating requires renumbering and is therefore expensive.
NSM shows good performance when tree is updated rarely. It is tuned to be fast for getting related nodes. It'is ideally suited for building multi-depth menu or categories for shop.
Suppose that we have a model Category
; a $node
variable is an instance of that model
and the node that we are manipulating. It can be a fresh model or one from database.
Node has following relationships that are fully functional and can be eagerly loaded:
parent
children
ancestors
descendants
Moving and inserting nodes includes several database queries, so it is highly recommended to use transactions.
IMPORTANT! As of v4.2.0 transaction is not automatically started
Another important note is that structural manipulations are deferred until you
hit save
on model (some methods implicitly call save
and return boolean result
of the operation).
If model is successfully saved it doesn't mean that node was moved. If your application
depends on whether the node has actually changed its position, use hasMoved
method:
if ($node->save()) {
$moved = $node->hasMoved();
}
When you simply creating a node, it will be appended to the end of the tree:
Category::create($attributes); // Saved as root
$node = new Category($attributes);
$node->save(); // Saved as root
In this case the node is considered a root which means that it doesn't have a parent.
// #1 Implicit save
$node->saveAsRoot();
// #2 Explicit save
$node->makeRoot()->save();
The node will be appended to the end of the tree.
If you want to make node a child of other node, you can make it last or first child.
In following examples, $parent
is some existing node.
There are few ways to append a node:
// #1 Using deferred insert
$node->appendToNode($parent)->save();
// #2 Using parent node
$parent->appendNode($node);
// #3 Using parent's children relationship
$parent->children()->create($attributes);
// #5 Using node's parent relationship
$node->parent()->associate($parent)->save();
// #6 Using the parent attribute
$node->parent_id = $parent->id;
$node->save();
// #7 Using static method
Category::create($attributes, $parent);
And only a couple ways to prepend:
// #1
$node->prependToNode($parent)->save();
// #2
$parent->prependNode($node);
You can make $node
to be a neighbor of the $neighbor
node using following methods:
$neighbor
must exists, target node can be fresh. If target node exists,
it will be moved to the new position and parent will be changed if it's required.
# Explicit save
$node->afterNode($neighbor)->save();
$node->beforeNode($neighbor)->save();
# Implicit save
$node->insertAfterNode($neighbor);
$node->insertBeforeNode($neighbor);
When using static method create
on node, it checks whether attributes contains
children
key. If it does, it creates more nodes recursively.
$node = Category::create([
'name' => 'Foo',
'children' => [
[
'name' => 'Bar',
'children' => [
[ 'name' => 'Baz' ],
],
],
],
]);
$node->children
now contains a list of created child nodes.
You can easily rebuild a tree. This is useful for mass-changing the structure of the tree.
Category::rebuildTree($data, $delete);
$data
is an array of nodes:
$data = [
[ 'id' => 1, 'name' => 'foo', 'children' => [ ... ] ],
[ 'name' => 'bar' ],
];
There is an id specified for node with the name of foo
which means that existing
node will be filled and saved. If node is not exists ModelNotFoundException
is
thrown. Also, this node has children
specified which is also an array of nodes;
they will be processed in the same manner and saved as children of node foo
.
Node bar
has no primary key specified, so it will be created.
$delete
shows whether to delete nodes that are already exists but not present
in $data
. By default, nodes aren't deleted.
As of 4.2.8 you can rebuild a subtree:
Category::rebuildSubtree($root, $data);
This constraints tree rebuilding to descendants of $root
node.
In some cases we will use an $id
variable which is an id of the target node.
Ancestors make a chain of parents to the node. Helpful for displaying breadcrumbs to the current category.
Descendants are all nodes in a sub tree, i.e. children of node, children of children, etc.
Both ancestors and descendants can be eagerly loaded.
// Accessing ancestors
$node->ancestors;
// Accessing descendants
$node->descendants;
It is possible to load ancestors and descendants using custom query:
$result = Category::ancestorsOf($id);
$result = Category::ancestorsAndSelf($id);
$result = Category::descendantsOf($id);
$result = Category::descendantsAndSelf($id);
In most cases, you need your ancestors to be ordered by the level:
$result = Category::defaultOrder()->ancestorsOf($id);
A collection of ancestors can be eagerly loaded:
$categories = Category::with('ancestors')->paginate(30);
// in view for breadcrumbs:
@foreach($categories as $i => $category)
<small>{{ $category->ancestors->count() ? implode(' > ', $category->ancestors->pluck('name')->toArray()) : 'Top Level' }}</small><br>
{{ $category->name }}
@endforeach
Siblings are nodes that have same parent.
$result = $node->getSiblings();
$result = $node->siblings()->get();
To get only next siblings:
// Get a sibling that is immediately after the node
$result = $node->getNextSibling();
// Get all siblings that are after the node
$result = $node->getNextSiblings();
// Get all siblings using a query
$result = $node->nextSiblings()->get();
To get previous siblings:
// Get a sibling that is immediately before the node
$result = $node->getPrevSibling();
// Get all siblings that are before the node
$result = $node->getPrevSiblings();
// Get all siblings using a query
$result = $node->prevSiblings()->get();
Imagine that each category has many
goods. I.e. HasMany
relationship is established.
How can you get all goods of $category
and every its descendant? Easy!
// Get ids of descendants
$categories = $category->descendants()->pluck('id');
// Include the id of category itself
$categories[] = $category->getKey();
// Get goods
$goods = Goods::whereIn('category_id', $categories)->get();
If you need to know at which level the node is:
$result = Category::withDepth()->find($id);
$depth = $result->depth;
Root node will be at level 0. Children of root nodes will have a level of 1, etc.
To get nodes of specified level, you can apply having
constraint:
$result = Category::withDepth()->having('depth', '=', 1)->get();
IMPORTANT! This will not work in database strict mode
All nodes are strictly organized internally. By default, no order is applied, so nodes may appear in random order and this doesn't affect displaying a tree. You can order nodes by alphabet or other index.
But in some cases hierarchical order is essential. It is required for retrieving ancestors and can be used to order menu items.
To apply tree order defaultOrder
method is used:
$result = Category::defaultOrder()->get();
You can get nodes in reversed order:
$result = Category::reversed()->get();
To shift node up or down inside parent to affect default order:
$bool = $node->down();
$bool = $node->up();
// Shift node by 3 siblings
$bool = $node->down(3);
The result of the operation is boolean value of whether the node has changed its position.
Various constraints that can be applied to the query builder:
Descendants constraints:
$result = Category::whereDescendantOf($node)->get();
$result = Category::whereNotDescendantOf($node)->get();
$result = Category::orWhereDescendantOf($node)->get();
$result = Category::orWhereNotDescendantOf($node)->get();
$result = Category::whereDescendantAndSelf($id)->get();
// Include target node into result set
$result = Category::whereDescendantOrSelf($node)->get();
Ancestor constraints:
$result = Category::whereAncestorOf($node)->get();
$result = Category::whereAncestorOrSelf($id)->get();
$node
can be either a primary key of the model or model instance.
After getting a set of nodes, you can convert it to tree. For example:
$tree = Category::get()->toTree();
This will fill parent
and children
relationships on every node in the set and
you can render a tree using recursive algorithm:
$nodes = Category::get()->toTree();
$traverse = function ($categories, $prefix = '-') use (&$traverse) {
foreach ($categories as $category) {
echo PHP_EOL.$prefix.' '.$category->name;
$traverse($category->children, $prefix.'-');
}
};
$traverse($nodes);
This will output something like this:
- Root
-- Child 1
--- Sub child 1
-- Child 2
- Another root
Also, you can build a flat tree: a list of nodes where child nodes are immediately after parent node. This is helpful when you get nodes with custom order (i.e. alphabetically) and don't want to use recursion to iterate over your nodes.
$nodes = Category::get()->toFlatTree();
Previous example will output:
Root
Child 1
Sub child 1
Child 2
Another root
Sometimes you don't need whole tree to be loaded and just some subtree of specific node. It is show in following example:
$root = Category::descendantsAndSelf($rootId)->toTree()->first();
In a single query we are getting a root of a subtree and all of its
descendants that are accessible via children
relation.
If you don't need $root
node itself, do following instead:
$tree = Category::descendantsOf($rootId)->toTree($rootId);
To delete a node:
$node->delete();
IMPORTANT! Any descendant that node has will also be deleted!
IMPORTANT! Nodes are required to be deleted as models, don't try do delete them using a query like so:
Category::where('id', '=', $id)->delete();
This will break the tree!
SoftDeletes
trait is supported, also on model level.
To check if node is a descendant of other node:
$bool = $node->isDescendantOf($parent);
To check whether the node is a root:
$bool = $node->isRoot();
Other checks:
$node->isChildOf($other);
$node->isAncestorOf($other);
$node->isSiblingOf($other);
$node->isLeaf()
You can check whether a tree is broken (i.e. has some structural errors):
$bool = Category::isBroken();
It is possible to get error statistics:
$data = Category::countErrors();
It will return an array with following keys:
oddness
-- the number of nodes that have wrong set of lft
and rgt
valuesduplicates
-- the number of nodes that have same lft
or rgt
valueswrong_parent
-- the number of nodes that have invalid parent_id
value that
doesn't correspond to lft
and rgt
valuesmissing_parent
-- the number of nodes that have parent_id
pointing to
node that doesn't existsSince v3.1 tree can now be fixed. Using inheritance info from parent_id
column,
proper _lft
and _rgt
values are set for every node.
Node::fixTree();
Imagine you have Menu
model and MenuItems
. There is a one-to-many relationship
set up between these models. MenuItem
has menu_id
attribute for joining models
together. MenuItem
incorporates nested sets. It is obvious that you would want to
process each tree separately based on menu_id
attribute. In order to do so, you
need to specify this attribute as scope attribute:
protected function getScopeAttributes()
{
return [ 'menu_id' ];
}
But now, in order to execute some custom query, you need to provide attributes that are used for scoping:
MenuItem::scoped([ 'menu_id' => 5 ])->withDepth()->get(); // OK
MenuItem::descendantsOf($id)->get(); // WRONG: returns nodes from other scope
MenuItem::scoped([ 'menu_id' => 5 ])->fixTree(); // OK
When requesting nodes using model instance, scopes applied automatically based on the attributes of that model:
$node = MenuItem::findOrFail($id);
$node->siblings()->withDepth()->get(); // OK
To get scoped query builder using instance:
$node->newScopedQuery();
Always use scoped query when eager loading:
MenuItem::scoped([ 'menu_id' => 5])->with('descendants')->findOrFail($id); // OK
MenuItem::with('descendants')->findOrFail($id); // WRONG
It is highly suggested to use database that supports transactions (like MySql's InnoDb) to secure a tree from possible corruption.
To install the package, in terminal:
composer require kalnoy/nestedset
For Laravel 5.5 and above users:
Schema::create('table', function (Blueprint $table) {
...
$table->nestedSet();
});
// To drop columns
Schema::table('table', function (Blueprint $table) {
$table->dropNestedSet();
});
For prior Laravel versions:
...
use Kalnoy\Nestedset\NestedSet;
Schema::create('table', function (Blueprint $table) {
...
NestedSet::columns($table);
});
To drop columns:
...
use Kalnoy\Nestedset\NestedSet;
Schema::table('table', function (Blueprint $table) {
NestedSet::dropColumns($table);
});
Your model should use Kalnoy\Nestedset\NodeTrait
trait to enable nested sets:
use Kalnoy\Nestedset\NodeTrait;
class Foo extends Model {
use NodeTrait;
}
If your previous extension used different set of columns, you just need to override following methods on your model class:
public function getLftName()
{
return 'left';
}
public function getRgtName()
{
return 'right';
}
public function getParentIdName()
{
return 'parent';
}
// Specify parent id attribute mutator
public function setParentAttribute($value)
{
$this->setParentIdAttribute($value);
}
If your tree contains parent_id
info, you need to add two columns to your schema:
$table->unsignedInteger('_lft');
$table->unsignedInteger('_rgt');
After setting up your model you only need to fix the tree to fill
_lft
and _rgt
columns:
MyModel::fixTree();
Copyright (c) 2017 Alexander Kalnoy
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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