Why does Rails .select alias change attributes to lowercase? - sql

Question

In our controller, we are trying to show a video series, which should return JSON similar to this:
{
id: 1,
name: "Series Name",
videos: [
id: 2,
name: "Video Name",
isInPlaylist: true,
isFavorite: false
]
}
We are adding the isInPlaylist and isInFavorite attributes via another table where we store data if a user has acted upon a video (rated it, favorited it, etc.).
videos = series.videos
.where('videos.is_live = true')
.joins("some join to user_videos join_table")
.select(
'videos.*,
coalesce(user_videos.rating, 0.0) as user_rating,
coalesce(user_videos.enqueue, \'false\') as isInPlaylist,
coalesce(user_videos.favorite, \'false\') as isFavorite'
)
Note that in our select statement those attributes are explicitly aliased as camel-cased values. However when we execute this query, these attributes are returned lower case instead:
{
isinplaylist: true,
isfavorite: false
}

Answer 1

This is not a Rails behavior, but rather a SQL behavior. Alias's are folded to lower case unless explicitly quoted. For an example, here is the output of a simple query in psql (the Postgres CLI program).
=# select created_at as theTimeNow from users limit 5;
thetimenow
----------------------------
2013-03-05 18:45:11.127092
2013-09-07 16:43:01.349823
2013-03-05 18:53:35.888306
2013-09-07 16:53:06.553129
2013-10-29 00:38:56.909418
(5 rows)
=# select created_at as "theTimeNow" from users limit 5;
theTimeNow
----------------------------
2013-03-05 18:45:11.127092
2013-09-07 16:43:01.349823
2013-03-05 18:53:35.888306
2013-09-07 16:53:06.553129
2013-10-29 00:38:56.909418
(5 rows)
Notice the column name outputs

Answer 2

Wrapping the alias in double quotes preserves case-sensitivity.
.select('foo as Bar') # => { bar: true }
.select('foo as "Bar"') # => { Bar: true }
The change to lower case is not an issue with the Rails .select() method but is enforced by the DB, in our case PostgreSQL, and is a practice called "Folding". Its worth noting that while PSQL will fold to lowercase letters, mySQL will fold to upper case letters.
I would argue however that it should still be included in the Rails API docs
¯\_(ツ)_/¯

Answer 3

I like you answer. The behaviour you see is rails default. As an alternative and
a more classic 'rails way' would be to use a json serializing library like jBuilder. It gives you lot more control over your API but your problem would be easy to fix in that using:
json.key_format! camelize: :lower
json.first_name 'David'
# => { "firstName": "David" }
To use something like this you would alias the columns as is_in_playlist format.
Here's a good place to start with jBuilder learning:
http://railscasts.com/episodes/320-jbuilder
Good tutorial on more json serializers:
http://railscasts.com/episodes/409-active-model-serializers