Comment by losvedir | Hacker News Reader

Comment by losvedir | Hacker News Reader

I tried adding a partial index the other day but Rails didn't seem to particularly like it. Are the examples here from Rails 4? (I'm on 3.2.16).

The issue I had was that, while the partial index syntax worked and actually did create it, it wasn't reflected anywhere in the generated schema. So I was worried that future developers wouldn't realize there was a partial index (we use schema.rb as the canonical reference of DB state), and if we ever get rid of migrations by condensing them into one big one we might miss that there should be a partial index on the column.

And changing the config to generate schema.sql instead of schema.rb didn't help. It's broken with the latest version of postgresql...

Switch from schema.rb to structure.sql by setting config.active_record.schema_format = :sql in your application config if you want to do anything remotely interesting with your schema.

The article covers only Rails 4.

Ah, bummer. Anyone have any luck getting partial indexes to work in Rails 3.2?

You can always execute arbitrary SQL in migrations. For instance:

    def up
      execute('ALTER TABLE people ADD INDEX ...')
    end

The one thing to keep in mind though is that if you use ruby schema format, your tests won't pick up those execute statements. In that case it's best to either use the sql format or re-run migrations in the test environment to set up the test db.

You could just do it manually:

    execute %{
      create index index_users_on_name
      on users (name)
      where state = 'NY';
    }

Upgrading from Rails 3.2 to Rails 4.0 takes very little time, assuming the gems you depend on are compatible (which they should be, by now, or you might want to look for replacement gems..)

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