magento2/app/code/Magento/OpenSearch/Model/OpenSearch.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
declare(strict_types=1);

namespace Magento\OpenSearch\Model;

/**
 * The purpose of this class is adding the support for opensearch version 2
 */

class OpenSearch extends SearchClient
{

    /**
     * Add mapping to OpenSearch index
     *
     * @param array $fields
     * @param string $index
     * @param string $entityType
     * @return void
     */
    public function addFieldsMapping(array $fields, string $index, string $entityType)
    {
        $params = [
            'index' => $index,
            'body' => [
                'properties' => [],
                'dynamic_templates' => $this->dynamicTemplatesProvider->getTemplates(),
            ],
        ];

        foreach ($this->applyFieldsMappingPreprocessors($fields) as $field => $fieldInfo) {
            $params['body']['properties'][$field] = $fieldInfo;
        }

        $this->getOpenSearchClient()->indices()->putMapping($params);
    }

    /**
     * Execute search by $query
     *
     * @param array $query
     * @return array
     */
    public function query(array $query): array
    {
        unset($query['type']);
        return $this->getOpenSearchClient()->search($query);
    }
}