Mattermost Migration Postgres restore fails

Troubleshooting
1

I am following the migration guide to move my mattermost server from one instance (u18.04+postgres10) to a new instance (u20.04+postgres13). Both installations are on the same server and schema version (5.36.1).

I am stuck on the DB migration part. I am using pg_dumpall --user=postgres > mattermost_db on the old box and psql -f mattermost_db mattermost on the new box but it fails with messages like:

psql:mattermost_db:40807: ERROR: relation "table_name" already exists, and
psql:mattermost_db:14: ERROR: role "mmuser" already exists

I know this is probably more of a postgres question than a mattermost question, but after a week of trying all sorts of things, I am really stuck.

Thank you so much in advance for any advice!

2

Hi, @mmadmin

Since you mentioned that you are currently stuck at the Postgres migration part specifically, may I know if you are dumping the data into a brand new database since you mentioned that you are getting the relation XXXX and role XXX already exists?

If not, were you trying to merge the Mattermost server together?

3

Thank you for your response. The new server is a brand new mattermost installation, I am not trying to merge two servers.

I have considered deleting all the tables on the new server, but did not know the potential [future] risks related to that… (Also, if I went that route, I would be unsure which tables not to delete, etc.).

My assumption is that there is a postgres command that would overwrite the tables on the target instance. [But I’ve had trouble finding the right postgres command(s) to do that.]

Thank you again! :slight_smile:

4

Hi, @mmadmin

So, that means that you are not dumping it into a fresh database. Am I getting the right idea?

I came across the article that suggests the following:

To rewrite data, you should either drop tables first or pg_dump -F c and pg_restore -c .

I’d recommend testing it on a staging instance first if you have any.

5

Hi @ahmaddanial Correct, I’m testing a new instance with the omni installation method, which of course sets up the target DB with the schema for a fresh install.

I will try your postgres commands and report back. Thank you so very much!!!

p.s. yes I’m testing with a cloned prod instance, and a new target instance. Thank you again. :slight_smile:

1 Like