Ask Connection to quote symbolic column names when building ORDER BY

[rdlugosz]

In some databases (e.g, mysql) column names referenced in ORDER BY clauses
should be quoted in case they are reserved words. This corrects an issue that
occurs when using the Model.order(:symbol) method if :symbol happens to be a reserved word (e.g., "key").

Most AR methods already handle this correctly, so calling Model.where(:key) does NOT fail
but Model.order(:key) does. This change impacts columns specified as symbols only.

This problem was originally reported as issue #2601. Tests pass.

Note to @tenderlove: it seems that this is something that could ultimately live within AREL, but based on what I saw the symbols are already strings and " ASC/DESC" is already attached to the column names before we get there. To be honest, after a few hours in the code I'm not completely clear as to where AR's intended responsibilities end and AREL's begin so if I'm missing something obvious pls inform.

PS - First Rails pull request so go easy on me... :)

[tenderlove]

I'll take a look at this. If we construct ASC / DESC nodes in the SQL AST, then quoting on a per db basis should be trivial. I need to look more closely though.

[rdlugosz]

Thx for taking a look.

Definitely an edge case but it can have you scratching your head when you hit it ...Especially since a column named "key" doesn't blow up sqlite - only mysql :/

[ahawkins]

@tenderlove that is definitely the way to do it. I always wondered why it doesn't work this way atm. Have you made any progress?

[lloeki]

How to order with quoted columns with Arel:

author_arel = Author.arel_table
email_attr = author_arel[:email]
Author.order(email_attr.asc)

[steveklabnik]

This will need a rebase.

[steveklabnik]

@thatRD PING! Are you interested in keeping this PR updated?

[rdlugosz]

Hey Steve - I'll do a rebase and see how well it aligns to the current code. If things have changed dramatically in this area I'll probably let it go.

[steveklabnik]

Allllrighty. Let me know if I can help.

[rdlugosz]

Looks like this issue has been fixed by timsly@633ea6a826cb5e587165f78d15770271cb39f670. I'm closing this PR and associated issue.