After installing this extension the folowing Mview subscriptions work correctly for "By Schedule" indexer mode when product entity is deleted:
<view id="hawksearch_products" class="HawkSearch\EsIndexing\Model\Indexer\Product" group="indexer">
<subscriptions>
<table name="catalog_category_product" entity_column="product_id" />
<table name="catalog_product_relation" entity_column="parent_id"/>
</subscriptions>
</view>Bug reference link: catalog_product_relation is unsuitable for mview