Viewing File: /home/maglabs/it/dev/tests/integration/testsuite/Magento/Indexer/Model/Config/_files/indexer.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:Indexer/etc/indexer.xsd">
    <indexer id="catalogsearch_fulltext" view_id="catalogsearch_fulltext"
             class="Magento\CatalogSearch\Model\Indexer\Fulltext"
             primary="first">

        <title translate="true">Catalog Search</title>
        <description translate="true">Rebuild Catalog product fulltext search index</description>

        <fieldset name="first" source="MagentoModule\ServiceClassOrRepositoryClass"
                  provider="Magento\Indexer\Model\Fieldset\ProductFieldset">
            <field name="title_alias" origin="title" xsi:type="searchable" dataType="text">
                <filter class="Magento\Framework\Search\Index\Filter\LowercaseFilter"/>
            </field>
            <field name="identifier" xsi:type="filterable" handler="Magento\Framework\Search\Index\Handler"/>
        </fieldset>

        <fieldset name="second" source="MagentoModule\ServiceClassOrRepositoryClass">
            <reference fieldset="first" from="id_field" to="second_entity_id"/>
            <field name="title" xsi:type="searchable"/>
        </fieldset>

        <saveHandler class="Magento\Cms\Model\Indexer\StoreResource"/>
        <structure class="Magento\Cms\Model\Indexer\IndexStructure"/>
        <dependencies>
            <indexer id="indexer_2"/>
        </dependencies>
    </indexer>
    <indexer id="indexer_2" view_id="indexer_2"
             class="Magento\Module\IndexerSecond">
        <dependencies>
            <indexer id="indexer_4" />
        </dependencies>
    </indexer>
    <indexer id="indexer_3" view_id="indexer_3"
             class="Magento\Module\IndexerThird">
    </indexer>
    <indexer id="indexer_4" view_id="indexer_4"
             class="Magento\Module\IndexerFourth">
    </indexer>
</config>