liferay-search-tuning-rankings index is missing from Elasticsearch after installing DXP 7.2 FP8+/SP3+

Environment

• Existing Liferay DXP 7.2 installations after moving to Fix Pack 8+/Service Pack 3+ (FP8+/SP3+) patch level
• Elasticsearch 6.x/7.x

Symptom

After installing DXP 7.2 FP8+/SP3+, the liferay-search-tuning-rankings index is missing from Elasticsearch.

Resolution

This index is replaced with one or more indexes which comply with the following naming pattern: liferay-<companyId>-search-tuning-rankings. Each new index stores Result Ranking entries for a given Virtual Instance. (The companyId belongs to a given Company record in your the database. It is displayed as "Instance ID" in the UI and represents the Virtual Instance.)

Existing data (documents) from the old index are migrated automatically at the first startup after the installation of FP8/SP3. Please refer to this guide for further details.