Hierarchical Categories — Facet Drill-Down Navigation

Hierarchical Categories

What You Get

Once configured, your search sidebar shows a collapsible drill-down facet. Visitors click any category value to zoom into that level — a breadcrumb trail and back button keep navigation intuitive:

How It Works

During ingestion, the module scans every entity_reference field on your node or Commerce product that points to a taxonomy_term. For each referenced term, it calls Drupal's loadAllParents() to walk the full ancestor chain, then assigns each level to a positional Solr field:

• item_list_element_1_name_sm — root / top-level ancestor (depth 1)
• item_list_element_2_name_sm — second level (depth 2)
• item_list_element_3_name_sm — third level (depth 3)
• … up to depth 6

You only assign a node to the most specific (leaf) term — the module finds all ancestors automatically. Multiple entity reference fields on the same content type are merged into the same positional fields.

Step 1 — Build Your Taxonomy Vocabulary

Go to Structure → Taxonomy in your Drupal admin. Create a new vocabulary (e.g., "Product Categories") or use an existing one.

1. Navigate to Structure → Taxonomy → Add vocabulary
2. Add your root terms first (e.g., "Electronics", "Clothing", "Books")
3. Add child terms — when adding a term, expand Relations and set its Parent term to the appropriate root
4. Add leaf terms at the deepest level you need (e.g., "Laptops" under "Computers" under "Electronics")
5. You can go up to 6 levels deep — deeper hierarchies are capped at depth 6

Step 2 — Add an Entity Reference Field to Your Content Type

Your content type needs an entity_reference field that references taxonomy terms from your vocabulary.

1. Go to Structure → Content types → [Your type] → Manage fields
2. Click Add field and choose Reference → Taxonomy term
3. Under Reference type, set Vocabularies to your taxonomy (e.g., "Product Categories")
4. Save the field settings
5. When editing a node, assign it to the most specific (leaf) category — the module walks up to find all ancestors

Step 3 — Ingest Your Content

The module picks up entity_reference → taxonomy_term fields automatically during ingestion. No additional configuration is needed on the module side.

• Real-time sync — enabled by default. Every time you save a node, the updated hierarchy is pushed immediately.
• Bulk ingestion — go to the Data Ingestion tab and click Ingest All Now to re-process your full content library if you added the field to existing content types.

Solr Fields Produced

For a product assigned to "Laptops" (child of "Computers" → child of "Electronics"), ingestion produces:

All fields use the _sm suffix — multi-valued string. If a node belongs to multiple leaf categories (e.g., "Laptops" and "Tablets"), each chain is merged: depth 2 will contain both "Laptops" and "Tablets" while depth 1 contains just "Computers".

Step 4 — Enable the Hierarchical Facet Widget

Once content is ingested, the item_list_element_* fields appear in your Facet Configuration table automatically.

1. Go to the Facet Mapping tab in your Opensolr Search settings
2. Find item_list_element_1_name_sm in the Facet Configuration section
3. Set the Widget column to Hierarchical
4. Set a Display Label (e.g., "Category", "Product Type")
5. Check the Enable checkbox to show the facet on the search page
6. Save the configuration

The search page will now show a collapsible drill-down facet. The Opensolr search engine automatically reads all item_list_element_N_name_sm fields for the selected depth. You only configure the depth-1 field — the rest are detected automatically.