Rails: How do I filter a ActiveRecord collection result without making new db queries?

Question

Say I have a Candle model with 'today' scope. The scope runs a few heavy conditions and gives me around 5k rows as the result.

today_candles = Candle.today

I want to later filter this collection with a column value. For eg:

aaa_candles = today_candles.where(type: 'AAA')
bbb_candles = today_candles.where(type: 'BBB')
...

But each of this filter is making a new db request as follows:

Candle.today.where(type: 'AAA')
Candle.today.where(type: 'BBB')
...

Is there a way to filter on the initial collection today_candles data without making new multiple db requests? It feels like a basic functionality but I cannot find it.

I am currently storing the collection as an array and then looping through them to filter and avoid multiple db calls. But this feels stupid.

Please note: I'm not sure if Rails does cache the AR collection and filter them without new db_queries in a production environment. I'm currently on webrick (development).

Answer 1

If you want to filter later - just treat relation as array. For example, filter with select:

today_candles.select { |x| x.type == 'AAA' }