Skip database migrations

[sosedoff]

I thought it would be useful to skip database migration task if the database is up to date.

Could utilize rake db:version and save it as a file somewhere at shared/.schema_version.

Ideas?

[skojin]

that's solve no problem, this task take same time as run empty rake db:migrate

[sosedoff]

The workaround could be an arbitrary execution of rake db:version after migration and saving the result to .migration file. During the next deployment, right before the migration, it should check the latest file under db/migrate and compare it to the saved version. Thats what i meant in the first place.

This could save around 3 seconds per deploy, which it a lot in most cases.

[skojin]

That work only in migration numbers sequenced, as in old rails. Now migration with old timestamp can be merged and migrated after more fresh migration. E.g. when some feature developed long time and merged into master. Rails have schema_versions table and check is each migration migrated.

[sosedoff]

Well, any suggestions then ?

[skojin]

Close this issue, leave work with migrations for rails. Now migrations even not most long task on deploy, assets packaging take more time.

[mikong]

If some improvements can save a few seconds here and there, it may be worth a look. Though in this case, migrations is a bit tricky. Even if we track the migrations independently from the database (say in a text file), there's still the danger that someone may run a migration manually at a server. Using mina should not prevent people from being able to do that.

I'm closing this for now. @sosedoff, @skojin, thanks for contributing to the project.

[rstacruz]

I think we can do this by checking the current deployed version's db/schema.rb and diffing it with the db/schema.rb to be deployed.

Reopening for discusisons :)

[sosedoff]

Good point, lets just do that.

[mikong]

For everyone's reference, let's take note that running rake db:migrate isn't exactly the same as checking schema.rb. If there's a new migration that somehow didn't update the schema.rb, then the behavior of running rake db:migrate vs checking schema.rb is different.

However...

If 99% of the cases commit their latest schema.rb (as everyone should!), then it's worth doing this for the benefit of most people. We'll still provide the classic rake db:migrate task in the form of rails:db_migrate:force, the same way we have rails:assets_precompile:force.

@sosedoff, @skojin, thanks for participating in the discussions :)

[rstacruz]

Done in v0.1.3.pre1, feel free to scrutinize and test it.

[sosedoff]

Great, will try it out.