ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR: column categories.search_priority does not exist

[david (David Taylor)]

Adding the multisite:migrate line is part of the #howto for multisite setups

Multisite configuration with Docker

While multisite is supported in the Discourse application, this is an advanced sysadmin setup. If you don’t know what you’re doing, do not set up multisite. The Discourse team is unable to provide multisite configuration support. If you wish to host multiple domains on a singled Docker setup, you’ll need a multisite configuration. Here are the basic building blocks for one. Understand hooks Multisite is a fairly advanced topic. Before attempting a multisite build, spend some time…

@pfaffman

how your multisite databases get migrated

Using the multisite:migrate command as described in the #howto

@pfaffman

I’m very confused how either these databases have been getting migrated

This is certainly surprising. I think you would be noticing issues if you hadn’t migrated for a whole year. If it was only a few weeks, then it might be possible to continue running on an old schema without too many errors. Have you modified one of the other templates to include multisite:migrate?