Drop initial prepared_at index, and create one with created_at
What does this MR do and why?
Initially we were going to query for every prepared_at = NULL row, but now we are going to do it based on the created_at time too.
We have a current index which is ID, and prepared_at = NULL.
This query is going to be run with each_batch
logic, for example: !121999 (diffs) (but also with where created_at > 1.day)
Following this guide, this is the creation of the new index, and dropping of the old index.
Follow up drop issue: #419917 (closed)
Follow up add issue: #419918 (closed)
Edited by Marc Shaw