Developer Documentation

CMS Integration

The Search module automatically integrates with the search functionality in the CMS, transparently upgrading requests to use Elasticsearch where possible.

(This feature is provided by ElasticPress, with additions from Altis.)

Querying with ElasticPress

By default, all search operations using the query APIs will transparently make use of the search index. This includes WP_Query, WP_User_Query, WP_Term_Query, and REST API queries, where the search parameter is specified (typically s).

You may want to manually enable this behaviour to use the search index for non-search queries. This may improve performance when running complex queries, such as meta queries, that would otherwise be too slow to do in the database.

Note: This usage is advanced, and may have wide-ranging implications for your queries, as you're querying the indexed fields rather than the original, source fields. Ensure you test this behaviour extensively.

To enable the use of ElasticPress integration, set the ep_integrate query param to true. (If the s (search) parameter is present ep_integrate will be set to true automatically.)

For example, the following query finds projects based on meta value, but does not contain search parameters. By default, ElasticPress would not be used, but is enabled explicitly by setting ep_integrate to true.

$posts = new WP_Query( [
	'ep_integrate' => true, // Use Elasticsearch.
	'post_type' => 'project',
	'meta_query' => [
		[
			'key' => 'color',
			'value' => [ 'blue', 'green' ],
			'compare' => 'IN'
		],
	],
] );

Note: This example may trigger Automated Code Review warnings due to the use of a meta query. While meta queries have a lower performance impact with Elasticsearch, it's important to test performance characteristics.

The automatic integration can be disabled on a per query basis by explicitly setting ep_integrate to false in the query arguments or on the pre_get_posts action. For example:

add_action( 'pre_get_posts', function ( WP_Query $query ) {
	// Avoid using Elasticsearch for the 'project' post type.
	if ( $query->is_search() && $query->get( 'post_type' ) === 'project' ) {
		$query->set( 'ep_integrate', false );;
	}
} );

Customising Searched Fields

Altis will search key content fields by default, including those defined in the field boosting config, depending on the type of content.

Using Query Parameters

WP_Query, WP_Term_Query and WP_User_Query support a search_fields parameter. This can be used to override the default searched fields and even to modify how the fields are boosted using the <field>^<boost value> syntax.

$posts = new WP_Query( [
	'ep_integrate' => true, // Use Elasticsearch.
	'post_type' => 'project',
	'search_fields' => [
		'post_title',
		'meta.client.value^2',
	],
] );

When using the search_fields parameter, the ep_search_fields filter will be run which can modify the list of searched fields.

Using Filters

As noted above the ep_search_fields filter can be used to further customise queries that use the search_fields parameter:

add_filter( 'ep_search_fields', function ( array $fields ) : array {
	$fields[] = 'alt';
	$fields[] = 'meta.keywords.value';
	return $fields;
} );

To modify the default searchable fields (when the search_fields parameter is not used) you need to use the ep_weighting_default_post_type_weights filter. The filter has 2 parameters, a keyed array of fields including their enabled status and weight, and the post type.

add_filter( 'ep_weighting_default_post_type_weights', function ( array $fields, string $post_type ) : array {
	// Add fields for all post types.
	$fields['meta.keywords.value'] = [
		'enabled' => true,
		'weight' => 1.0,
	];

	// Add fields for specific post types.
	switch ( $post_type ) {
		case 'attachment':
			$fields['alt'] = [
				'enabled' => true,
				'weight' => 1.5,
			];
			break;
		case 'project':
			$fields['meta.client.value'] = [
				'enabled' => true,
				'weight' => 1.0,
			];
			break;
	}

	return $fields;
}, 10, 2 );