unnecessary parens when combining multiple "UNION ALL" (mysql)

[bughit]

https://github.com/brianhempel/active_record_union/pull/4#issuecomment-163079230

to repro:

use gem 'active_record_union', github: 'odedniv/active_record_union' in a rails (with mysql) project then with any model run the following:

User.where(id: 1).union(User.where(id: 2), User.where(id: 3)).to_sql

SELECT `users`.* FROM ( (SELECT `users`.* FROM `users` WHERE `users`.`id` = 1) UNION (SELECT `users`.* FROM `users` WHERE `users`.`id` = 2) UNION (SELECT `users`.* FROM `users` WHERE `users`.`id` = 3) ) `users`

User.where(id: 1).union_all(User.where(id: 2), User.where(id: 3)).to_sql

SELECT `users`.* FROM ( ( (SELECT `users`.* FROM `users` WHERE `users`.`id` = 1) UNION ALL (SELECT `users`.* FROM `users` WHERE `users`.`id` = 2) ) UNION ALL (SELECT `users`.* FROM `users` WHERE `users`.`id` = 3) ) `users`

note the extra grouping with UNION ALL

[kbrock]

Please let me know if #510 meets your needs (and if it works for you)

[matthewd]

Per #523, Arel development is moving to rails/rails.

If this issue is still relevant, please consider reopening it over there. (Note that the Rails repository does not accept feature request issues, and requires reproduction steps that rely on Active Record's documented API.)

[kbrock]

Merged into Rails