If you are using Magento 2.3.0 you have to use elasticsearch 5.x. Refer to offical doc.
Composer of Magento 2.3.0
{
"name": "magento/module-elasticsearch",
"description": "N/A",
"require": {
"php": "~7.1.3||~7.2.0",
"magento/module-advanced-search": "100.3.*",
"magento/module-catalog": "103.0.*",
"magento/module-catalog-search": "101.0.*",
"magento/module-customer": "102.0.*",
"magento/module-eav": "102.0.*",
"magento/module-search": "101.0.*",
"magento/module-store": "101.0.*",
"magento/module-catalog-inventory": "100.3.*",
"magento/framework": "102.0.*",
"elasticsearch/elasticsearch": "~2.0|~5.1"
},
"suggest": {
"magento/module-config": "101.1.*"
},
"type": "magento2-module",
"license": [
"OSL-3.0",
"AFL-3.0"
],
"autoload": {
"files": [
"registration.php"
],
"psr-4": {
"Magento\\Elasticsearch\\": ""
}
},
"version": "100.3.0"
}
If you want to use elasticsearch 6.x you need to upgrade your magento to v2.3.1.
Composer of Magento 2.3.1
{
"name": "magento/module-elasticsearch",
"description": "N/A",
"require": {
"php": "~7.1.3||~7.2.0",
"magento/module-advanced-search": "100.3.*",
"magento/module-catalog": "103.0.*",
"magento/module-catalog-search": "101.0.*",
"magento/module-customer": "102.0.*",
"magento/module-eav": "102.0.*",
"magento/module-search": "101.0.*",
"magento/module-store": "101.0.*",
"magento/module-catalog-inventory": "100.3.*",
"magento/framework": "102.0.*",
"elasticsearch/elasticsearch": "~2.0|~5.1|~6.1"
},
"suggest": {
"magento/module-config": "101.1.*"
},
"type": "magento2-module",
"license": [
"OSL-3.0",
"AFL-3.0"
],
"autoload": {
"files": [
"registration.php"
],
"psr-4": {
"Magento\\Elasticsearch\\": ""
}
},
"version": "100.3.1"
}
Best Answer
Go to
Open Catalog Search and select Elastic Search 5.0 +
Flush Magento Cache , do a full reindex, and check again .
If you see Magento 2.3.0 release notes LINK ,
If you still having issues than install Elastic Search 5.x with this steps magento provides Link. It is easy , just follow the steps . This link Link has the steps for ubuntu .