Read magento 2 there is no such adapter elasticsearch for more information.
Magento 2.1.10 contains almost 40 security fixes and functional enhancements so it will bring a lot of benefits of
your online store owner to upgrade to this latest version. But along with this, you may run into errors.
How to fix the there is no such adapter error
# run this query UPDATE core_config_data set value = 'mysql' where path='catalog/search/engine'; # and run these commands php -f bin/magento setup:upgrade php -f bin/magento cache:flush php -f bin/magento indexer:reindex
Magento 2.3.1 adds support for Elasticsearch 6.x and it is enabled by default. Magento still provides connectivity for Elasticsearch 2.x and 5.x but these must be enabled in order to use these versions. Elasticsearch 2.x is still supported but strongly discouraged. If you must run Elasticsearch 2.x or 5.x with Magento 2.3.1, you must change the Elasticsearch PHP client.
Change the Elasticsearch Client
If you need to work with Elasticsearch 5.x, run the following command:
composer require "elasticsearch/elasticsearch:~5.1"
If you need to work with Elasticsearch 2.x, run the following command:
composer require "elasticsearch/elasticsearch:~2.0"
To re-enable Elasticsearch 6.x, run the following command:
composer require "elasticsearch/elasticsearch:~6.1"
Then configure Elasticsearch within Magento Admin.
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