Modifying columns

I think it is a reasonable expectation that it would be possible to:

• rename a column
• change the data type
• add or drop the null constraint
• change the default

And probably other things that I have not thought of.

I would imagine the syntax for doing this would be something like

 knex.Schema.table('table_name', function (t) {
        t.string('my_column').renameTo('something_else');
        t.string('my_column').changeTo('text');
        t.string('my_column').nullable() < adds nullable if not already present
        t.string('my_column').notNullable() < removes nullable if present
        t.string('my_column').defaultTo('whatever') < adds or updates the default
  });

Maybe there needs to be something extra in the chain, possibly at the knex.Schema.table level to indicate that this is a modify statement not an add.

I realise that this is tricky to implement across various databases, especially in SQLite where you have to create a whole new table, but in a system which requires migrations, without these tools it is going to be necessary to use knex.raw and write all the migrations for each DB supported, which sort of defeats the point of having a nice ORM especially one which is about to support migrations.

[tkellen]

Switching between MySQL and PostgreSQL seamlessly is a pipe dream that will never happen for anyone on a meaningful scale ever. All database systems have strengths and weaknesses. It makes absolutely no sense to limit yourself to a subset that works across both so you can arbitrarily decide to switch between one or the other.

ActiveRecord doesn’t do migrations “right”. There is a huge set of functionality it doesn’t provide a DSL for. You are right that more human effort has been dumped into ActiveRecord’s migration system though. The reason for that is simple numbers.

Knex:

ActiveRecord:

My question remains. Where is the value in these DSLs? Anything you want to migrate can be expressed in SQL. You don’t need to build some half-baked sugar on top of it. People have been talking about altering columns here for 3 years. Meanwhile SQL has been trucking along doing the same thing just fine for 30.

Also, RE: switching between PostgreSQL and MySQL, what happens if you decide to move from javascript to ruby? How much time will it take you to transcribe all of your SQL migrations from one silly pointless DSL to another? Maybe we should write a portable DSL, you say? That’s SQL.

[RobertWarrenGilmore]

I would love to see an API like table.modifyColumn('myCol').notNullable().defaultTo('hello').