Products added to a category are not shown at the frontend.

[addinm]

Preconditions (*)

1. Magento CE <= 2.2.6
2. Magento Commerce Edition <= 2.2.6

Steps to reproduce (*)

1. Run magento indexer:reindex to make all indexes up to date.
2. Switch all indexes to the "Update Scheduled" mode.
3. Set up Cron.
4. Create a simple product (visible at the frontend, qty > 0)
5. Create a category.
6. Go to the frontend and make sure that the category is empty.
7. Open the created category (step 4) and assign the created product to it.
8. Save category changes.
9. Wait until Cron reindexes category changes or run magento indexer:reindex catalog_category_product.
10. Open the category at the frontend.

Expected result (*)

1. Category must contain the product.

Actual result (*)

1. The category is still empty

The problem

It looks like the category uses the information from the 'catalogsearch_fulltext' index because running magento indexer:reindex catalogsearch_fulltext solves the issue.

The solution

The solution is simple: track changes in the "catalog_category_product" table and update the "catalogsearch_fulltext_cl" changelog table.

This can be done by adding an additional subscriber:
<table name="catalog_category_product" entity_column="product_id" />
to the vendor/magento/module-catalog-search/etc/mview.xml file.

So the updated file should look this way:

<?xml version="1.0" encoding="UTF-8"?>
<!--
/**
 * 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:Mview/etc/mview.xsd">
    <view id="catalogsearch_fulltext" class="\Magento\CatalogSearch\Model\Indexer\Mview\Action" group="indexer">
        <subscriptions>
            <table name="catalog_product_entity" entity_column="entity_id" />
            <table name="catalog_product_entity_int" entity_column="entity_id" />
            <table name="catalog_product_entity_decimal" entity_column="entity_id" />
            <table name="catalog_product_entity_text" entity_column="entity_id" />
            <table name="catalog_product_entity_varchar" entity_column="entity_id" />
            <table name="catalog_product_entity_datetime" entity_column="entity_id" />
            <table name="catalog_product_website" entity_column="product_id" />
            <table name="cataloginventory_stock_item" entity_column="product_id" />
            <table name="catalog_product_bundle_selection" entity_column="parent_product_id" />
            <table name="catalog_product_super_link" entity_column="product_id" />
            <table name="catalog_product_link" entity_column="product_id" />
            <table name="catalog_category_product" entity_column="product_id" />
        </subscriptions>
    </view>
</config>

[magento-engcom-team]

Hi @addinm. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

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• Information on your environment
• Steps to reproduce
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Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

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@addinm do you confirm that you was able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

[magento-engcom-team]

Hi @engcom-backlog-andrii. Thank you for working on this issue.
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[hostep]

I was reading the unpublished release notes for Magento 2.2.7 yesterday, and they seem to mention a fix in there which sound very similar to this bug report:

You can now see category changes on the storefront as expected after the changes have been saved. Previously, Magento did not display changes to product categories on the storefront until reindexing occurred even if update on schedule was set and the cache had been cleaned.

Maybe best to re-test your bug when Magento 2.2.7 gets released tomorrow?

[magento-engcom-team]

@engcom-backlog-andrii Thank you for verifying the issue. Based on the provided information internal tickets MAGETWO-96667, MAGETWO-96668 were created

[addinm]

@hostep Thank you for the information, I'll re-check this on 2.2.7 tomorrow.