Rename tables for rails convention

[BenMorganIO]

No description provided.

[magnusvk]

This looks good, though I'd want to split up the migration. As this stands, the whole migration will run in one database migration which feels dangerous and I don't think is necessary. If we had one migration per rename, it would run each in its own transaction.

[BenMorganIO]

@magnusvk I think this will be the last time I separate things out...

[magnusvk]

:)

[grzlus]

Using DISTINCT that way, will not work in PostgreSQL (if I undestand correctly, why distinct is used there). In documentation, we have example:

SELECT DISTINCT ON (location) location, time, report
    FROM weather_reports
    ORDER BY location, time DESC;

So when we want to show records with unique spree_product.id then we need to add ON before field name, but this is not compatible with other DBs.

[BenMorganIO]

@grzlus If we add the ON keyword, then we could definitely move this to Arel, but you're right, this won't be compatible with other DBs. I think I'll just make an if statement for database type. Its not nice, but it'll do :(

[grzlus]

This will not be so easy: https://github.com/rails/arel/blob/master/lib/arel/visitors/to_sql.rb#L298 Only PostgreSQL has implemented visit function for distinct_on

You need to guess what DB is used and use distinct/distinct on 😞

[cbrunsdon]

Cleaning up these commits isn't going to be worth the effort to get them into core, the majority of the important functionality of #289 already got in, so just killing this.