I worked on migrating our MySQL system to PostgreSQL using pgloader ( https://pgloader.io/ ).
There were some hiccups, things that needed clarification in documentation, and some additional processes that needed to be done outside of the system to get everything we need in place, it was a amazing help. Not sure the project would've been possible without it.
Data mapping from PostgreSQL to PostgreSQL as in the article isn't nearly as bad as going between systems. We took a full extended outage and didn't preload any data. There were many dry runs before hand and validation before hand, but the system wasn't so mission critical that we couldn't afford to shutoff the system for a couple of hours.
We also ended up using pgloader. Its not without its friction either. For example the concurrency/number of rows setting seems broken out the gate, and its like playing darts with a blindfold on to get it to run without running out of memory. But being able to read the source, github actions, and overall at least I could debug my problems, or find others who had the same issue.
There were some hiccups, things that needed clarification in documentation, and some additional processes that needed to be done outside of the system to get everything we need in place, it was a amazing help. Not sure the project would've been possible without it.
Data mapping from PostgreSQL to PostgreSQL as in the article isn't nearly as bad as going between systems. We took a full extended outage and didn't preload any data. There were many dry runs before hand and validation before hand, but the system wasn't so mission critical that we couldn't afford to shutoff the system for a couple of hours.