While upgrading from Mysource Matrix version 3.20.1 - 3.22.1 I needed to make some changes to the database in Postgres.

Do you think I had any recollection on how this might be done?  Of course not.

After a few attempts I got it back to this....

Open the terminal window and ssh to the server (although you should already be there during the upgrade, this is just incase you are really starting from the beginning)

Type 'psql -d mysource_matrix -U matrix' and press enter

psql  this tells the terminal that you want to go to the postgres command line

-d denotes which database you will be making changes to, so if you're not working with mysource_matrix add your own database name

-U dentoes the user you are performing the commands as.

Both of these default to the current user for both the database and the user, so you need to specify both.