ElasticPress - Polylang

elasticpress-polylang.php

// Filter Elasticsearch posts by current language
add_filter( 'ep_formatted_args', function($formatted_args, $args) {
	$formatted_args['post_filter']['bool']['must'][] = [
		'term' => [
			'lang' => pll_current_language()
		]
	];
	return $formatted_args;
}, 10, 2);

// Add language data to Elasticsearch database
add_filter('ep_post_sync_args_post_prepare_meta', function($post_args, $post_id) {
	$post_args['lang'] = pll_get_post_language($post_id);
	return $post_args;
}, 10, 2);