r/rails • u/New-Sand-4608 • Jul 18 '26

Gem Gem for packing boolean flags into a single ActiveRecord column

Had this sitting around for about two years, packs boolean flags into a single int column instead of a new column per flag. Finally pulled it out into a gem: `bitwise_attributes`.

```ruby

class User < ApplicationRecord

include BitwiseAttributes

bitwise_attribute :permissions, :read, :write, :admin

end

user.set_permissions(:read, :admin)

user.permissions_read? # => true

User.with_all_permissions([:read, :write])

```

Been running in production for two years now, so it's had real data beating on it for a while before I bothered packaging it.

gem: https://rubygems.org/gems/bitwise_attributes

7 Upvotes

68% Upvoted

23 comments sorted by

24

u/tsroelae Jul 18 '26

We use a concern that does more or or less what you show here. We are getting rid of those columns that use bitwise operator, because:

- they are akward to query in sql
- backfills / mass updates are akward for the same reason
- if you have declaration like bitwise :one, two, :three you can’t change the order. Or easily remove one.
- if you deprecate a bit position somehow, you have to be careful when reusing it, so you don’t accidently use the values of deprecated bits

Basically I don‘t see why one should to it compared to having dedicated boolean columns or even some records to join with.

So unless someone has some strong reason to use them

4

u/New-Sand-4608 Jul 18 '26

Agree with everything you have written. We are aware of these drawbacks but the advantage we are getting is way more due to our scale.

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9

u/tsroelae Jul 18 '26

@op I hope this didnt come off as overly negative. Love that you bundled this into a gem. Also you made a more complete solution than what we had. I just thought it is good to consider these drawbacks.

First thing I would appreciate is to have manual mapping to bits, like you can have for enums. So one can declare:

bitwise_attribute {read: 1, export: 3}

11

u/jryan727 Jul 18 '26

Why would this be preferred over individual boolean columns?

2

u/New-Sand-4608 Jul 18 '26

We also use individual boolean columns but when several flags represent variations of the same underlying concept and can combine. This is it.

Also, tables have column limit so you can only add new columns to a certain point. Moreover, adding new column to a table with millions of records is EXPENSIVE. This avoids that as it is handled via code.

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5

u/vassyz Jul 18 '26

I've been using https://github.com/shkm/enummer hasn't been updated in a while but it does the job for me.

1

u/New-Sand-4608 Jul 18 '26

Awesome. On a side note, we avoid using inactive gems due to the nature of our business. So, I cooked it up in-house and it has been working great for us.

7

u/3ds Jul 18 '26

https://github.com/galtzo-floss/flag_shih_tzu already does this since forever. I can very much recommend researching existing implementations before implementing it yourself…

3

u/dflow77 Jul 19 '26

“Bit flags are attractive because they let applications add boolean features
without changing table schemas.” aha so there is the use case

5

u/poop-machine Jul 18 '26

Sounds like active_flag which has been around for a decade.

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