On any Magento version, because some extensions only work with flat tables there is a risk if you disable flat tables. If you know that you have some extensions that use Flat Catalog indexers, you may need to take that into consideration when setting those values to "No".
This article describes how to solve site performance issues and slow running and stuck crons caused by flat tables and indexers having been enabled.
AFFECTED PRODUCTS AND VERSIONS
- Magento Commerce Cloud 2.1.x and above
- Magento Commerce (On-Premise) 2.1.x and above
- Magento Open Source 2.1.x and above
Issue
Flat indexers can cause:
- Heavy SQL load and site performance issues.
- Long running and stuck crons.
Cause
Flat tables and indexers enabled.
Solution
Starting with Magento 2.1.x and above, the use of a flat catalog is no longer a best practice and is not recommended. Continued use of this feature is known to cause performance degradation and other indexing issues. To disable the flat catalog:
- In the Magento Admin, navigate to Stores > Settings > Configuration.
- In the panel on the left under Catalog, choose Catalog.
- Expand the Storefront section, and do the following:
- Set Use Flat Catalog Category to No.
- Set Use Flat Catalog Product to No.
- When complete, click Save Config. Then when prompted, refresh the cache.
- Flush cache by running
php bin/magento cache:flush
If you can't change the Use Flat Catalog Category and Use Flat Catalog Product to No because the options are greyed out disable flat indexers in app/etc/config.php:
- Run this command to make sure all indexers are set to Update by schedule:
php bin/magento indexer:set-mode schedule - Edit
app/etc/config.phpand locate the lines withflat_catalog_productandflat_catalog_category- change them from 1 to 0 to disable them. - Run the command
php bin/magento app:config:import - Run this command to confirm that the flat indexers are disabled:
php bin/magento indexer:status - Flush cache by running
php bin/magento cache:flush