I'm maintaining a database cluster with 10s of millions of partial indexes, many of which contain a LIKE pattern. Each table in the cluster has several of these

I'm maintaining a database cluster with 10s of millions of partial indexes, many of which contain a LIKE pattern. Each table in the cluster has several of these partial indexes. Because of all of these partial indexes, we became CPU bound. For the longest time, we thought all of the CPU was going to evaluating the LIKE patterns. Eventually, I decided to generate a flame graph of our database and discovered that we were only spending 0.3% of the time evaluating the partial index predicates. In turns out most of the CPU usage was evenly split between looking up the metadata of the index and in parsing the index predicate. So the index expression itself doesn't really matter, but having lots of these indexes can become an issue.