Update plugin search algorithm for Elasticsearch version 7

[robfelty]

The plugin search on wordpress.org (and also in wp-admin) is powered by Elasticsearch. Currently the index is running on Elasticsearch version 2, which is quite outdated. We would like to move the index to Elasticsearch version 7, in order to be more up to date. In testing this change, we noticed that some internal scoring changes in Elasticsearch resulted in different results, giving higher weight to the boosting parts of the search query, such as ranking plugins with higher install counts higher. In order to keep the results as similar as possible to the current results, these changes give slightly higher weight to the text based parts of the query, giving similar results to the current query when running on Elasticsearch 7.

Deploying this change should be done at the same time that the active version of the index is updated to the new version running Elasticsearch 7.

I am attaching a patch to the plugin search algorithm.

[robfelty]

patch for the plugin search

[dd32]

Thanks for the ticket @robfelty!

This change looks good to me, and I'm happy to deploy it whenever you'd like to coincide with the migration. Feel free to organise that directly with me or one of my other team mates, I'll ping you directly to organise a time.

[dd32]

In 12362:

Plugin Directory: Search: Alter the Elastic Search query to provide a more expected result set on the new ES index.

For more detailed reasonings, see the ticket below.

Props robfelty.
Fixes #6677.