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staudenmeir / laravel-adjacency-list

Recursive Laravel Eloquent relationships with CTEs
MIT License
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Laravel Adjacency List

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This Laravel Eloquent extension provides recursive relationships for trees and graphs using common table expressions (CTE).

Compatibility

Installation

composer require staudenmeir/laravel-adjacency-list:"^1.0"

Use this command if you are in PowerShell on Windows (e.g. in VS Code):

composer require staudenmeir/laravel-adjacency-list:"^^^^1.0"

Versions

Laravel Package
11.x 1.21
10.x 1.13
9.x 1.12
8.x 1.9
7.x 1.5
6.x 1.3
5.8 1.1
5.5–5.7 1.0

Usage

The package offers recursive relationships for traversing two types of data structures:

Trees: One Parent per Node (One-to-Many)

Use the package to traverse a tree structure with one parent per node. Use cases might be recursive categories, a page hierarchy or nested comments.

Supports Laravel 5.5+.

Getting Started

Consider the following table schema for hierarchical data in trees:

Schema::create('users', function (Blueprint $table) {
    $table->id();
    $table->unsignedBigInteger('parent_id')->nullable();
});

Use the HasRecursiveRelationships trait in your model to work with recursive relationships:

class User extends Model
{
    use \Staudenmeir\LaravelAdjacencyList\Eloquent\HasRecursiveRelationships;
}

By default, the trait expects a parent key named parent_id. You can customize it by overriding getParentKeyName():

class User extends Model
{ 
    public function getParentKeyName()
    {
        return 'parent_id';
    }
}

By default, the trait uses the model's primary key as the local key. You can customize it by overriding getLocalKeyName():

class User extends Model
{
    public function getLocalKeyName()
    {
        return 'id';
    }
}

Included Relationships

The trait provides various relationships:

$ancestors = User::find($id)->ancestors;

$users = User::with('descendants')->get();

$users = User::whereHas('siblings', function ($query) {
    $query->where('name', 'John');
})->get();

$total = User::find($id)->descendants()->count();

User::find($id)->descendants()->update(['active' => false]);

User::find($id)->siblings()->delete();

Trees

The trait provides the tree() query scope to get all models, beginning at the root(s):

$tree = User::tree()->get();

treeOf() allows you to query trees with custom constraints for the root model(s). Consider a table with multiple separate lists:

$constraint = function ($query) {
    $query->whereNull('parent_id')->where('list_id', 1);
};

$tree = User::treeOf($constraint)->get();

You can also pass a maximum depth:

$tree = User::tree(3)->get();

$tree = User::treeOf($constraint, 3)->get();

You can also chaperone tree relationships to load ancestors and parent relationships already present in the tree to (potentially) reduce N+1 queries:

$users = User::tree(3)->get();

$users->loadTreeRelationships();

Or with toTree():

$users = User::tree(1)->get();

$tree = $users->loadTreeRelationships()->toTree();

Filters

The trait provides query scopes to filter models by their position in the tree:

$noLeaves = User::hasChildren()->get();

$noRoots = User::hasParent()->get();

$leaves = User::isLeaf()->get();
$leaves = User::doesntHaveChildren()->get();

$roots = User::isRoot()->get();

Order

The trait provides query scopes to order models breadth-first or depth-first:

$tree = User::tree()->breadthFirst()->get();

$descendants = User::find($id)->descendants()->depthFirst()->get();

Depth

The results of ancestor, bloodline, descendant and tree queries include an additional depth column.

It contains the model's depth relative to the query's parent. The depth is positive for descendants and negative for ancestors:

$descendantsAndSelf = User::find($id)->descendantsAndSelf()->depthFirst()->get();

echo $descendantsAndSelf[0]->depth; // 0
echo $descendantsAndSelf[1]->depth; // 1
echo $descendantsAndSelf[2]->depth; // 2

Change the column name by overriding getDepthName() if your table already contains a depth column:

class User extends Model
{
    public function getDepthName()
    {
        return 'depth';
    }
}
Depth Constraints

You can use the whereDepth() query scope to filter models by their relative depth:

$descendants = User::find($id)->descendants()->whereDepth(2)->get();

$descendants = User::find($id)->descendants()->whereDepth('<', 3)->get();

Queries with whereDepth() constraints that limit the maximum depth still build the entire (sub)tree internally. Use withMaxDepth() to set a maximum depth that improves query performance by only building the requested section of the tree:

$descendants = User::withMaxDepth(3, function () use ($id) {
    return User::find($id)->descendants;
});

This also works with negative depths (where it's technically a minimum):

$ancestors = User::withMaxDepth(-3, function () use ($id) {
    return User::find($id)->ancestors;
});

Path

The results of ancestor, bloodline, descendant and tree queries include an additional path column.

It contains the dot-separated path of local keys from the query's parent to the model:

$descendantsAndSelf = User::find(1)->descendantsAndSelf()->depthFirst()->get();

echo $descendantsAndSelf[0]->path; // 1
echo $descendantsAndSelf[1]->path; // 1.2
echo $descendantsAndSelf[2]->path; // 1.2.3

Change the column name by overriding getPathName() if your table already contains a path column:

class User extends Model
{
    public function getPathName()
    {
        return 'path';
    }

You can also customize the path separator by overriding getPathSeparator():

class User extends Model
{
    public function getPathSeparator()
    {
        return '.';
    }
}

Custom Paths

You can add custom path columns to the query results:

class User extends Model
{
    public function getCustomPaths()
    {
        return [
            [
                'name' => 'slug_path',
                'column' => 'slug',
                'separator' => '/',
            ],
        ];
    }
}

$descendantsAndSelf = User::find(1)->descendantsAndSelf;

echo $descendantsAndSelf[0]->slug_path; // user-1
echo $descendantsAndSelf[1]->slug_path; // user-1/user-2
echo $descendantsAndSelf[2]->slug_path; // user-1/user-2/user-3

You can also reverse custom paths:

class User extends Model
{
    public function getCustomPaths()
    {
        return [
            [
                'name' => 'reverse_slug_path',
                'column' => 'slug',
                'separator' => '/',
                'reverse' => true,
            ],
        ];
    }
}

Nested Results

Use the toTree() method on a result collection to generate a nested tree:

$users = User::tree()->get();

$tree = $users->toTree();

This recursively sets children relationships:

[
  {
    "id": 1,
    "children": [
      {
        "id": 2,
        "children": [
          {
            "id": 3,
            "children": []
          }
        ]
      },
      {
        "id": 4,
        "children": [
          {
            "id": 5,
            "children": []
          }
        ]
      }
    ]
  }
]

Initial & Recursive Query Constraints

You can add custom constraints to the CTE's initial and recursive query. Consider a query where you want to traverse a tree while skipping inactive users and their descendants:

$tree = User::withQueryConstraint(function (Builder $query) {
    $query->where('users.active', true);
}, function () {
    return User::tree()->get();
});

You can also add a custom constraint to only the initial or recursive query using withInitialQueryConstraint()/ withRecursiveQueryConstraint().

Additional Methods

The trait also provides methods to check relationships between models:

$rootUser = User::create(['parent_id' => null]); 
$firstLevelUser = User::create(['parent_id' => $rootUser->id]); 
$secondLevelUser = User::create(['parent_id' => $firstLevelUser->id]);  

$isChildOf = $secondLevelUser->isChildOf($firstLevelUser); // Output: true
$isParentOf = $rootUser->isParentOf($firstLevelUser); // Output: true
$depthRelatedTo = $secondLevelUser->getDepthRelatedTo($rootUser); // Output: 2

Custom Relationships

You can also define custom relationships to retrieve related models recursively.

HasManyOfDescendants

Consider a HasMany relationship between User and Post:

 class User extends Model
 {
     public function posts()
     {
         return $this->hasMany(Post::class);
     }
 }

Define a HasManyOfDescendants relationship to get all posts of a user and its descendants:

class User extends Model
{
    public function recursivePosts()
    {
        return $this->hasManyOfDescendantsAndSelf(Post::class);
    }
}

$recursivePosts = User::find($id)->recursivePosts;

$users = User::withCount('recursivePosts')->get();

Use hasManyOfDescendants() to only get the descendants' posts:

class User extends Model
{
    public function descendantPosts()
    {
        return $this->hasManyOfDescendants(Post::class);
    }
}
BelongsToManyOfDescendants

Consider a BelongsToMany relationship between User and Role:

 class User extends Model
 {
     public function roles()
     {
         return $this->belongsToMany(Role::class);
     }
 }

Define a BelongsToManyOfDescendants relationship to get all roles of a user and its descendants:

class User extends Model
{
    public function recursiveRoles()
    {
        return $this->belongsToManyOfDescendantsAndSelf(Role::class);
    }
}

$recursiveRoles = User::find($id)->recursiveRoles;

$users = User::withCount('recursiveRoles')->get();

Use belongsToManyOfDescendants() to only get the descendants' roles:

class User extends Model
{
    public function descendantRoles()
    {
        return $this->belongsToManyOfDescendants(Role::class);
    }
}
MorphToManyOfDescendants

Consider a MorphToMany relationship between User and Tag:

 class User extends Model
 {
     public function tags()
     {
         return $this->morphToMany(Tag::class, 'taggable');
     }
 }

Define a MorphToManyOfDescendants relationship to get all tags of a user and its descendants:

class User extends Model
{
    public function recursiveTags()
    {
        return $this->morphToManyOfDescendantsAndSelf(Tag::class, 'taggable');
    }
}

$recursiveTags = User::find($id)->recursiveTags;

$users = User::withCount('recursiveTags')->get();

Use morphToManyOfDescendants() to only get the descendants' tags:

class User extends Model
{
    public function descendantTags()
    {
        return $this->morphToManyOfDescendants(Tag::class, 'taggable');
    }
}
MorphedByManyOfDescendants

Consider a MorphedByMany relationship between Category and Post:

 class Category extends Model
 {
     public function posts()
     {
         return $this->morphedByMany(Post::class, 'categorizable');
     }
 }

Define a MorphedByManyOfDescendants relationship to get all posts of a category and its descendants:

class Category extends Model
{
    public function recursivePosts()
    {
        return $this->morphedByManyOfDescendantsAndSelf(Post::class, 'categorizable');
    }
}

$recursivePosts = Category::find($id)->recursivePosts;

$categories = Category::withCount('recursivePosts')->get();

Use morphedByManyOfDescendants() to only get the descendants' posts:

class Category extends Model
{
    public function descendantPosts()
    {
        return $this->morphedByManyOfDescendants(Post::class, 'categorizable');
    }
}
Intermediate Scopes

You can adjust the descendants query (e.g. child users) by adding or removing intermediate scopes:

User::find($id)->recursivePosts()->withTrashedDescendants()->get();

User::find($id)->recursivePosts()->withIntermediateScope('active', new ActiveScope())->get();

User::find($id)->recursivePosts()->withIntermediateScope(
    'depth',
    function ($query) {
        $query->whereDepth('<=', 10);
    }
)->get();

User::find($id)->recursivePosts()->withoutIntermediateScope('active')->get();
Usage outside of Laravel

If you are using the package outside of Laravel or have disabled package discovery for staudenmeir/laravel-cte, you need to add support for common table expressions to the related model:

class Post extends Model
{
    use \Staudenmeir\LaravelCte\Eloquent\QueriesExpressions;
}

Deep Relationship Concatenation

You can include recursive relationships into deep relationships by concatenating them with other relationships using staudenmeir/eloquent-has-many-deep. This works with Ancestors, Bloodline and Descendants relationships (Laravel 9+).

Consider a HasMany relationship between User and Post and building a deep relationship to get all posts of a user's descendants:

User → descendants → User → has many → Post

Install the additional package, add the HasRelationships trait to the recursive model and define a deep relationship:

class User extends Model
{
    use \Staudenmeir\EloquentHasManyDeep\HasRelationships;
    use \Staudenmeir\LaravelAdjacencyList\Eloquent\HasRecursiveRelationships;

    public function descendantPosts(): \Staudenmeir\EloquentHasManyDeep\HasManyDeep
    {
        return $this->hasManyDeepFromRelations(
            $this->descendants(),
            (new static)->posts()
        );
    }

    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

$descendantPosts = User::find($id)->descendantPosts;

At the moment, recursive relationships can only be at the beginning of deep relationships:

Known Issues

MariaDB doesn't yet support correlated CTEs in subqueries. This affects queries like User::whereHas('descendants') or User::withCount('descendants').

Graphs: Multiple Parents per Node (Many-to-Many)

You can also use the package to traverse graphs with multiple parents per node that are defined in a pivot table. Use cases might be a bill of materials (BOM) or a family tree.

Supports Laravel 9+.

Getting Started

Consider the following table schema for storing directed graphs as nodes and edges:

Schema::create('nodes', function (Blueprint $table) {
    $table->id();
});

Schema::create('edges', function (Blueprint $table) {
    $table->unsignedBigInteger('source_id');
    $table->unsignedBigInteger('target_id');
    $table->string('label');
    $table->unsignedBigInteger('weight');
});

Use the HasGraphRelationships trait in your model to work with graph relationships and specify the name of the pivot table:

class Node extends Model
{
    use \Staudenmeir\LaravelAdjacencyList\Eloquent\HasGraphRelationships;

    public function getPivotTableName(): string
    {
        return 'edges';
    }
}

By default, the trait expects a parent key named parent_id and child key named child_id in the pivot table. You can customize them by overriding getParentKeyName() and getChildKeyName():

class Node extends Model
{
    public function getParentKeyName(): string
    {
        return 'source_id';
    }

    public function getChildKeyName(): string
    {
        return 'target_id';
    }
}

By default, the trait uses the model's primary key as the local key. You can customize it by overriding getLocalKeyName():

class Node extends Model
{
    public function getLocalKeyName(): string
    {
        return 'id';
    }
}

Included Relationships

The trait provides various relationships:

$ancestors = Node::find($id)->ancestors;

$nodes = Node::with('descendants')->get();

$nodes = Node::has('children')->get();

$total = Node::find($id)->descendants()->count();

Node::find($id)->descendants()->update(['active' => false]);

Node::find($id)->parents()->delete();

Pivot Columns

Similar to BelongsToMany relationships, you can retrieve additional columns from the pivot table besides the parent and child key:

class Node extends Model
{
    public function getPivotColumns(): array
    {
        return ['label', 'weight'];
    }
}

$nodes = Node::find($id)->descendants;

foreach ($nodes as $node) {
    dump(
        $node->pivot->label,
        $node->pivot->weight
    );
}

Cycle Detection

If your graph contains cycles, you need to enable cycle detection to prevent infinite loops:

class Node extends Model
{
    public function enableCycleDetection(): bool
    {
        return true;
    }
}

You can also retrieve the start of a cycle, i.e. the first duplicate node. With this option, the query results include an is_cycle column that indicates whether the node is part of a cycle:

class Node extends Model
{
    public function enableCycleDetection(): bool
    {
        return true;
    }

    public function includeCycleStart(): bool
    {
        return true;
    }
}

$nodes = Node::find($id)->descendants;

foreach ($nodes as $node) {
    dump($node->is_cycle);
}

Subgraphs

The trait provides the subgraph() query scope to get the subgraph of a custom constraint:

$constraint = function ($query) {
    $query->whereIn('id', $ids);
};

$subgraph = Node::subgraph($constraint)->get();

You can pass a maximum depth as the second argument:

$subgraph = Node::subgraph($constraint, 3)->get();

Order

The trait provides query scopes to order nodes breadth-first or depth-first:

$descendants = Node::find($id)->descendants()->breadthFirst()->get();

$descendants = Node::find($id)->descendants()->depthFirst()->get();

Depth

The results of ancestor, descendant and subgraph queries include an additional depth column.

It contains the node's depth relative to the query's parent. The depth is positive for descendants and negative for ancestors:

$descendantsAndSelf = Node::find($id)->descendantsAndSelf()->depthFirst()->get();

echo $descendantsAndSelf[0]->depth; // 0
echo $descendantsAndSelf[1]->depth; // 1
echo $descendantsAndSelf[2]->depth; // 2

Change the column name by overriding getDepthName() if your table already contains a depth column:

class Node extends Model
{
    public function getDepthName(): string
    {
        return 'depth';
    }
}
Depth Constraints

You can use the whereDepth() query scope to filter nodes by their relative depth:

$descendants = Node::find($id)->descendants()->whereDepth(2)->get();

$descendants = Node::find($id)->descendants()->whereDepth('<', 3)->get();

Queries with whereDepth() constraints that limit the maximum depth still build the entire (sub)graph internally. Use withMaxDepth() to set a maximum depth that improves query performance by only building the requested section of the graph:

$descendants = Node::withMaxDepth(3, function () use ($id) {
    return Node::find($id)->descendants;
});

This also works with negative depths (where it's technically a minimum):

$ancestors = Node::withMaxDepth(-3, function () use ($id) {
    return Node::find($id)->ancestors;
});

Path

The results of ancestor, descendant and subgraph queries include an additional path column.

It contains the dot-separated path of local keys from the query's parent to the node:

$descendantsAndSelf = Node::find(1)->descendantsAndSelf()->depthFirst()->get();

echo $descendantsAndSelf[0]->path; // 1
echo $descendantsAndSelf[1]->path; // 1.2
echo $descendantsAndSelf[2]->path; // 1.2.3

Change the column name by overriding getPathName() if your table already contains a path column:

class Node extends Model
{
    public function getPathName(): string
    {
        return 'path';
    }
}

You can also customize the path separator by overriding getPathSeparator():

class Node extends Model
{
    public function getPathSeparator(): string
    {
        return '.';
    }
}

Custom Paths

You can add custom path columns to the query results:

class Node extends Model
{
    public function getCustomPaths(): array
    {
        return [
            [
                'name' => 'slug_path',
                'column' => 'slug',
                'separator' => '/',
            ],
        ];
    }
}

$descendantsAndSelf = Node::find(1)->descendantsAndSelf;

echo $descendantsAndSelf[0]->slug_path; // node-1
echo $descendantsAndSelf[1]->slug_path; // node-1/node-2
echo $descendantsAndSelf[2]->slug_path; // node-1/node-2/node-3

You can also reverse custom paths:

class Node extends Model
{
    public function getCustomPaths(): array
    {
        return [
            [
                'name' => 'reverse_slug_path',
                'column' => 'slug',
                'separator' => '/',
                'reverse' => true,
            ],
        ];
    }
}

Nested Results

Use the toTree() method on a result collection to generate a nested tree:

$nodes = Node::find($id)->descendants;

$tree = $nodes->toTree();

This recursively sets children relationships:

[
  {
    "id": 1,
    "children": [
      {
        "id": 2,
        "children": [
          {
            "id": 3,
            "children": []
          }
        ]
      },
      {
        "id": 4,
        "children": [
          {
            "id": 5,
            "children": []
          }
        ]
      }
    ]
  }
]

Initial & Recursive Query Constraints

You can add custom constraints to the CTE's initial and recursive query. Consider a query where you want to traverse a node's descendants while skipping inactive nodes and their descendants:

$descendants = Node::withQueryConstraint(function (Builder $query) {
    $query->where('nodes.active', true);
}, function () {
    return Node::find($id)->descendants;
});

You can also add a custom constraint to only the initial or recursive query using withInitialQueryConstraint()/ withRecursiveQueryConstraint().

Deep Relationship Concatenation

You can include recursive relationships into deep relationships by concatenating them with other relationships using staudenmeir/eloquent-has-many-deep (Laravel 9+).

Consider a HasMany relationship between Node and Post and building a deep relationship to get all posts of a node's descendants:

Node → descendants → Node → has many → Post

Install the additional package, add the HasRelationships trait to the recursive model and define a deep relationship:

class Node extends Model
{
    use \Staudenmeir\EloquentHasManyDeep\HasRelationships;
    use \Staudenmeir\LaravelAdjacencyList\Eloquent\HasGraphRelationships;

    public function descendantPosts(): \Staudenmeir\EloquentHasManyDeep\HasManyDeep
    {
        return $this->hasManyDeepFromRelations(
            $this->descendants(),
            (new static)->posts()
        );
    }

    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

$descendantPosts = Node::find($id)->descendantPosts;

At the moment, recursive relationships can only be at the beginning of deep relationships:

Known Issues

MariaDB doesn't yet support correlated CTEs in subqueries. This affects queries like Node::whereHas('descendants') or Node::withCount('descendants').

Package Conflicts

Contributing

Please see CONTRIBUTING and CODE OF CONDUCT for details.