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Declarative schema management provides some nice properties that aren't present in imperative/migration-based tools. I'm the creator of a widely-used declarativ

Declarative schema management provides some nice properties that aren't present in imperative/migration-based tools. I'm the creator of a widely-used declarative tool for MySQL/MariaDB called Skeema, and I wrote a blog post summarizing some advantages a few years back: https://www.skeema.io/blog/2019/01/18/declarative/ https://www.skeema.io/blog/2019/01/18/declarative/ You are correct that renames are problematic with declarative tools, but in production renames are problematic in general because of deploy-order concerns. Best practice with schema changes is always for applications to be able to work fine with both the old and new schema, and renames typically break this, as most ORMs / database interface layers don't support this. So renames already require a special process at companies that even allow renames in production (in my experience, many do not). Skeema treats them as an out-of-band activity; it gets out of your way and you handle the rename outside of the tool, and then can use Skeema to update your repo afterwards. If you accidentally try to do a rename inside the tool, it will treat it as a drop-and-create, but it prevents the push from proceeding since it detects it is destructive.

satyrnein 5y ago
I find Skeema pretty compelling, but I couldn't figure out one aspect: Say I'm adding a gender column to my employees table. I see how Skeema would be an alternative to running DDL in a migration. But I would end up still needing a migration to backfill the data. So I could use Skeema, but I still need migrations (we also occasionally fix data due to bugs, etc). At that point, we were less motivated to add an additional process. Is that what Skeema users do, or is there some other approach, or maybe this isn't what I should be doing in the first place?
- evanelias 5y ago
  Currently, Skeema doesn't interact with DML or provide anything to help here. But that means you're free to use whatever solution you'd like, and Skeema won't get in your way, even if you store your DML in the same repo or even same subdirectories. Part of the reason for this is that some of Skeema's users are quite large, and larger MySQL users already have in-house solutions for row data migrations. When your tables are huge and/or sharded, a data migration consists of a lot more complexity than just putting an UPDATE statement into a .sql file :) I do agree it would be good to have some options in Skeema for DML at various scales, and it's something I plan to start approaching in the future, hopefully later this year. Overall my approach with Skeema's roadmap has been to first get DDL right for tables, then get DDL right for other types of objects (finally complete), and only then move on to considering automation for other areas (whether that be DML, or something like managing users/grants, database global variables, etc).

satyrnein 5y ago

I find Skeema pretty compelling, but I couldn't figure out one aspect: Say I'm adding a gender column to my employees table. I see how Skeema would be an alternative to running DDL in a migration. But I would end up still needing a migration to backfill the data. So I could use Skeema, but I still need migrations (we also occasionally fix data due to bugs, etc). At that point, we were less motivated to add an additional process. Is that what Skeema users do, or is there some other approach, or maybe this isn't what I should be doing in the first place?

evanelias 5y ago
Currently, Skeema doesn't interact with DML or provide anything to help here. But that means you're free to use whatever solution you'd like, and Skeema won't get in your way, even if you store your DML in the same repo or even same subdirectories. Part of the reason for this is that some of Skeema's users are quite large, and larger MySQL users already have in-house solutions for row data migrations. When your tables are huge and/or sharded, a data migration consists of a lot more complexity than just putting an UPDATE statement into a .sql file :) I do agree it would be good to have some options in Skeema for DML at various scales, and it's something I plan to start approaching in the future, hopefully later this year. Overall my approach with Skeema's roadmap has been to first get DDL right for tables, then get DDL right for other types of objects (finally complete), and only then move on to considering automation for other areas (whether that be DML, or something like managing users/grants, database global variables, etc).