ElasticPress 4.0.0 Search Algorithm

elasticpress-search-algorithm-4.0.php

<?php
/**
 * These functions can be used by ElasticPress 3.5.5+ users wanting to
 * use the search algorithm introduced as default in EP 4.0
 */

/**
 * Change the search algorithm to the one introduced in ElasticPress 4.0.
 *
 * @param array  $query         Current query
 * @param array  $query_vars    Query variables
 * @param string $search_text   Search text
 * @param array  $search_fields Search fields
 * @return array New query
 */
function ep_custom_change_search_algorithm( $query, $args, $search_text, $search_fields ) {
	return [
		'bool' => [
			'should' => [
				[
					'multi_match' => [
						'query'  => $search_text,
						'type'   => 'phrase',
						'fields' => $search_fields,
						'boost'  => apply_filters( 'ep_match_phrase_boost', 3, $search_fields, $args ),
					],
				],
				[
					'multi_match' => [
						'query'     => $search_text,
						'fields'    => $search_fields,
						'boost'     => apply_filters( 'ep_match_boost', 1, $search_fields, $args ),
						'fuzziness' => apply_filters( 'ep_match_fuzziness', 'auto', $search_fields, $args ),
						'operator'  => 'and',
					],
				],
				[
					'multi_match' => [
						'query'       => $search_text,
						'type'        => 'cross_fields',
						'fields'      => $search_fields,
						'boost'       => apply_filters( 'ep_match_cross_fields_boost', 1, $search_fields, $args ),
						'analyzer'    => 'standard',
						'tie_breaker' => 0.5,
						'operator'    => 'and',
					],
				],
			],
		],
	];
}
add_filter( 'ep_formatted_args_query', 'ep_custom_change_search_algorithm', 10, 4 );

/**
 * Apply `1` as the weight for the cross_field clause.
 *
 * @param string $weighted_field The field and its weight as used in the ES query.
 * @param string $field          Field name
 * @param string $weight         Weight value
 * @param array  $fieldset       Current subset of formatted ES args
 * @return array New weighted field string
 */
function ep_custom_adjust_weight_for_cross_fields( $weighted_field, $field, $weight, $fieldset ) {
	if ( 'cross_fields' === $fieldset['type'] ) {
		$weighted_field = "{$field}^1";
	}
	return $weighted_field;
}
add_filter( 'ep_query_weighting_fields', 'ep_custom_adjust_weight_for_cross_fields', 10, 5 );