BUG #17652: Performance degradation after migrating from v13.4 to v14.4

The following bug has been logged on the website:

Bug reference:      17652
Logged by:          Michael Guissine
Email address:      mguissine@gmail.com
PostgreSQL version: 14.4
Operating system:   AWS RDS
Description:

Hello,

We recently upgraded our AWS RDS instances to PG 14.4 and are seeing weird
performance degradation. The issue seems to be isolated to one specific use
case which is querying partitioned table with a large number of elements in
the IN clause. In our setup, we observed that Postgres is switching from
Index Scan to Bitmap Index Scan/Bitmap Heap Scan if the number of elements
in the IN clause is above 60, below 60 the Index Scan is performed on all
partitions.

Query and query plan are attached below. We also tried to turn off
enable_bitmapscan and observed that query is performing well which was our
experience in the previous version (pg 13.4)

https://explain.depesz.com/s/F587

Thank you!