Recursive CTEs for Hierarchical Data in Laravel | Mohamed Said [ ![Mohamed Said](https://cdn.msaied.com/01KT78WE565VEMM3PSNQAAB0MH.png) Mohamed Said Laravel Backend Engineer ](https://www.msaied.com) [ Home ](https://www.msaied.com) [ Projects ](https://www.msaied.com/projects) [ Articles ](https://www.msaied.com/articles) [ Certificates ](https://www.msaied.com/certificates) [ Contact ](https://www.msaied.com#contact-section) [ ](https://github.com/EG-Mohamed) [ Home ](https://www.msaied.com) [ Projects ](https://www.msaied.com/projects) [ Articles ](https://www.msaied.com/articles) [ Certificates ](https://www.msaied.com/certificates) [ Contact ](https://www.msaied.com#contact-section) [ home ](https://www.msaied.com) [ articles ](https://www.msaied.com/articles) Recursive CTEs and Hierarchical Data in Laravel with PostgreSQL On this page 1. [ The Problem With Nested Sets and Closure Tables ](#the-problem-with-nested-sets-and-closure-tables) 2. [ The Schema ](#the-schema) 3. [ Writing the Recursive CTE ](#writing-the-recursive-cte) 4. [ Integrating With Eloquent ](#integrating-with-eloquent) 5. [ Fetching Ancestors (Upward Traversal) ](#fetching-ancestors-upward-traversal) 6. [ Guarding Against Infinite Loops ](#guarding-against-infinite-loops) 7. [ Performance Notes ](#performance-notes) 8. [ Takeaways ](#takeaways) ![Recursive CTEs and Hierarchical Data in Laravel with PostgreSQL](https://cdn.msaied.com/607/ac508dd27011f0f2c57b0bee7707b740.png) #laravel #postgresql #eloquent #database Recursive CTEs and Hierarchical Data in Laravel with PostgreSQL ================================================================= 29 Aug 2026 3 min read ![Mohamed Said](https://cdn.msaied.com/01KT78WE565VEMM3PSNQAAB0MJ.jpg) Mohamed Said Table of contents 1. [ 01 The Problem With Nested Sets and Closure Tables ](#the-problem-with-nested-sets-and-closure-tables) 2. [ 02 The Schema ](#the-schema) 3. [ 03 Writing the Recursive CTE ](#writing-the-recursive-cte) 4. [ 04 Integrating With Eloquent ](#integrating-with-eloquent) 5. [ 05 Fetching Ancestors (Upward Traversal) ](#fetching-ancestors-upward-traversal) 6. [ 06 Guarding Against Infinite Loops ](#guarding-against-infinite-loops) 7. [ 07 Performance Notes ](#performance-notes) 8. [ 08 Takeaways ](#takeaways) The Problem With Nested Sets and Closure Tables ----------------------------------------------- Most Laravel tutorials reach for nested sets or closure tables when modelling hierarchical data. Both work, but they add write complexity: every insert or move must update auxiliary columns or rows. PostgreSQL's `WITH RECURSIVE` gives you the same read power from a plain adjacency-list table—just a `parent_id` foreign key—with no extra bookkeeping. ### The Schema ```sql CREATE TABLE categories ( id BIGSERIAL PRIMARY KEY, parent_id BIGINT REFERENCES categories(id) ON DELETE CASCADE, name TEXT NOT NULL ); CREATE INDEX idx_categories_parent ON categories(parent_id); ``` In Laravel the migration is straightforward: ```php Schema::create('categories', function (Blueprint $table) { $table->id(); $table->foreignId('parent_id')->nullable()->constrained('categories')->cascadeOnDelete(); $table->string('name'); }); ``` ### Writing the Recursive CTE A recursive CTE has two parts joined by `UNION ALL`: the **anchor** (the starting row) and the **recursive member** (the self-join that walks the tree). ```sql WITH RECURSIVE subtree AS ( -- anchor: the root we care about SELECT id, parent_id, name, 0 AS depth FROM categories WHERE id = :root_id UNION ALL -- recursive member: children of the current frontier SELECT c.id, c.parent_id, c.name, s.depth + 1 FROM categories c JOIN subtree s ON c.parent_id = s.id ) SELECT * FROM subtree ORDER BY depth, name; ``` PostgreSQL iterates until no new rows are produced, so you get the full subtree in one round-trip. ### Integrating With Eloquent The cleanest approach is a **local scope** that swaps the base query for the CTE result: ```php class Category extends Model { public function scopeSubtreeOf(Builder $query, int $rootId): Builder { $sql = addBinding($rootId, 'from') ->orderBy('depth') ->orderBy('name'); } } ``` Usage is ergonomic: ```php $tree = Category::subtreeOf(42)->get(); ``` Because `fromSub` replaces the `FROM` clause, all subsequent Eloquent constraints (`where`, `with`, `select`) still compose correctly. ### Fetching Ancestors (Upward Traversal) Flip the join direction to walk toward the root: ```php public function scopeAncestorsOf(Builder $query, int $leafId): Builder { $sql = addBinding($leafId, 'from') ->orderByDesc('depth'); } ``` This is ideal for breadcrumb generation: `Category::ancestorsOf($currentId)->pluck('name')` returns the path from root to leaf. ### Guarding Against Infinite Loops PostgreSQL stops when the recursive member returns zero rows, but a corrupted `parent_id` cycle will loop forever. Add a depth guard: ```sql WHERE s.depth < 50 -- inside the recursive member's WHERE clause ``` Or use the `CYCLE` clause available in PostgreSQL 14+: ```sql WITH RECURSIVE subtree AS ( ... ) CYCLE id SET is_cycle USING path SELECT * FROM subtree WHERE NOT is_cycle; ``` ### Performance Notes - The index on `parent_id` is critical; PostgreSQL uses it on every recursive iteration. - For very wide trees (thousands of siblings per level), add a composite index `(parent_id, name)` to cover the `ORDER BY`. - `EXPLAIN (ANALYZE, BUFFERS)` will show a `CTE Scan` node; ensure it reads from the index rather than a sequential scan on the base table. Takeaways --------- - A plain adjacency-list table plus `WITH RECURSIVE` handles most tree use-cases without closure tables or nested sets. - Wrap the CTE in a `fromSub` scope so Eloquent constraints remain composable. - Walk downward for subtrees, upward for breadcrumbs—same pattern, reversed join. - Add a depth guard or PostgreSQL 14's `CYCLE` clause to protect against corrupt data. - Index `parent_id` (and optionally cover with sort columns) to keep recursive iterations fast. Found this useful? [ ](https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.msaied.com%2Farticles%2Frecursive-ctes-and-hierarchical-data-in-laravel-with-postgresql&text=Recursive+CTEs+and+Hierarchical+Data+in+Laravel+with+PostgreSQL) [ ](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.msaied.com%2Farticles%2Frecursive-ctes-and-hierarchical-data-in-laravel-with-postgresql) Frequently Asked Questions ---------------------------- 3 questions Q01 Can I eager-load relationships on the result of a recursive CTE scope? Yes. Because the scope uses `fromSub` to replace the FROM clause rather than wrapping the entire query, Eloquent's `with()` calls still append the standard relationship sub-queries. Just chain `->with('products')` as normal after `subtreeOf()`. Q02 Is `WITH RECURSIVE` significantly slower than a closure table for reads? For moderate tree depths (under ~20 levels) and a proper index on `parent_id`, the difference is negligible. Closure tables win on very deep trees with millions of rows because they trade write cost for a flat read. Profile with `EXPLAIN ANALYZE` for your specific data shape before optimising prematurely. Q03 Does this approach work with MySQL? MySQL 8.0+ supports `WITH RECURSIVE`, so the SQL is portable. However, the `CYCLE` detection clause is PostgreSQL-specific. On MySQL you must rely on a depth guard in the WHERE clause of the recursive member. Continue reading More Articles --------------- [ View all ](https://www.msaied.com/articles) [ ![Laravel API Resources: Sparse Fieldsets, Cursor Pagination, and Per-Route Rate Limiting](https://cdn.msaied.com/606/93349b03f4527b9100157c6774bb4ce2.png) laravel api eloquent ### Laravel API Resources: Sparse Fieldsets, Cursor Pagination, and Per-Route Rate Limiting Go beyond basic JsonResource usage. 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