yaml_db | Rails plugin for a database-independent dump format | Database library

updating sql to gem 'mysql2', '~> 0.4.10' fixed the issue

Heroku doesn't support Ruby 2.3.1, 2.3.3 or 2.4.0

Look at your log:

You need to specify the file as a Thor template. Rails uses Thor templates for generating templates with ERB style code inside them.

Replace:
copy_file 'model.rb', "app/models/#{file_name}.rb"

With:
template 'model.rb.tt', "app/models/#{file_name}.rb"

By adding the .tt extension you're telling the generator to handle the file as a Thor template, which will interpret the Ruby code (ERB style) inside the file and then create a file with that same name minus the .tt extension. Any file you have without the .tt extension the generator will copy wholesale, without executing any of the code inside.

A useful tip: Sometimes you want to leave some ERB code inside a Thor template file without it being executed. By default any ERB style tags inside a .tt file will be process and in it's place a string will be written to the output file. You can avoid the processing of ERB tags but using a double percent sign in the tag.

For example, lets say you have a file named foo.erb.tt, which will create the file foo.erb when your generator runs. Let's also say we have a article_name variable and it's value is Breaking News

If you put <%= article_name %> in the file it will write Breaking News to the foo.erb.

If you put <%%= article_name %> (notice the %%) it will write <%= article_name %>to the foo.erb.

I found the following reference handy when learning this stuff.

• Rails Application Templates article at Rails Guides.
• Creating and Customizing Rails Generators & Templates article at Rails Guides.
• Thor Actions Docs these are the commands used in our template.rb file.

Thor comes with several actions that help with script and generator tasks. You might be familiar with them since some came from Rails Templates. They are: say, ask, yes?, no?, add_file, remove_file, copy_file, template, directory, inside, run, inject_into_file and a couple more.

I faced a similar situation some time ago, with an app designed with database multitenancy. To merge all data into a single database I ended up creating a rake task, that would go through every record and association and recreate them in the new database.

The task had two arguments SOURCE and DESTINATION, and it would be run like: rake db:merge SOURCE=some_database DESTINATION=new_database. The task was run for each database I needed to merge.

Inside the rake task the idea was something like this:

I would agree with the people saying use the built in database tools to do it. Or figure out if there's a way to tell the database to export to CSV, and then import that way.

However, if you really want a database agnostic way, here's another way: use your own API.

By that I mean that in 2017 your Rails app really should not just output HTML, but also output JSON. Maybe you want to write a SPA type app in the future, or a mobile app. Making sure there's a Javascript representation of the object, in addition to the HTML version, is a great idea.

So, if you have /projects in your app, write a script that requests /projects as JSON. Save each object as its own file, then in your remote system post everything back in.

If there's anything not in the JSON representation (ie you don't list all the users on the project) make sure to hit those endpoints too and save everything to a separate JSON file.

Then write a player script that POSTS all those files to your destination service.

That's one way to do it. There other way is to write it entirely in Ruby in ActiveRecord - this might be useful as some kind of user data export functionality, so this could be an awesome way to do it too, but in my mind, "can we build a Javascript frontend or mobile app for this?" is usually asked way before, "can the user get their data out" ;)

Well this is weird, but solved.

The 'process' method that puma has been griping about is normally defined in the uploader/processing.rb file in the carrierwave gem.

I say normally because in mine, it wasn't. Somehow I wound up with a malformed processing.rb file which did not contain 'process' (nor it's evil twin 'process!') as it should have. I've strained my brain over how this happened and can't really account for it.

Nevertheless, grabbing a good copy of the file and replacing my malformed one with it solved the problem.

Seems almost anticlimactic, doesn't it?

Anyhow, onward and I'd like to thank @Md.FarhanMemon and @SachinSingh for their taking the time to respond and ask questions.

You're copying a database, Rails really shouldn't have anything to do with the process (and as you're seeing, it just gets in the way).

Instead, put on your DBA hat and copy the database without bothering with Rails. Dump the data using pg_dump and then restore the data with pg_restore. The database's backup/restore tools know all about foreign keys, triggers, extensions, and anything else that Railsy tools don't understand.