decided not to migrate Moodle from MySQL to Postgres

Though Moodle is believed to have better performance on PostgreSQL than on MySQL, 

There is a migrate tool

https://bobcares.com/blog/moodle-mysql-to-postgres/

But could have issues,

Some troubles you may find when using this tool:

If there is any object in the current database (columns, tables,...) not included in the XMLDB schema or the other way around the dbtransfer won't be executed until these objects are removed (this may happen if Moodle has been upgraded from earlier versions, if some plugin hasn't been correctly uninstalled...).

https://docs.moodle.org/405/en/Database_transfer

Also, "Depending on the size of your database, the process may take several hours."

So, decided not to migrate to Postgres at the moment.

Edit - update in Aug 2026 - ChatGPT says, (private URL for my reference - https://chatgpt.com/c/6a9267b3-5d78-83ee-9bed-f3db27750248 ) "My current assessment is that a PostgreSQL migration before the Moodle 5.3 upgrade is unlikely to deliver enough performance improvement to justify the migration effort and testing risk. I'd spend the effort on caching, PHP tuning, and perhaps a RAM upgrade first."

Change	Expected impact
MySQL → PostgreSQL	0–10%
MySQL tuning	5–20%
Redis/MUC tuning	10–50%
Faster CPU	Often noticeable
More RAM (8 → 16 GB)	Often more useful than DB migration