SQLite doesn't cast 1/0 to true and false

[cllns]

Describe the bug

I'm trying to select_append a boolean from a subquery (here just rendered as TRUE for simplicity) in my app, which is built on SQLite.

For background, SQLite doesn't have a boolean type (nor true nor false), and the convention is to use 1 and 0 instead. I used bool::cast to wrap the subquery, but it's still returning 1 or 0.

To Reproduce

require "rom"

Types = Dry.Types()
module Structs
  class ArticleWithParamsBoolVisible < ROM::Struct
    attribute :title, Types::String
    attribute :visible, Types::Params::Bool
  end

  class ArticleWithRegularBoolVisible < ROM::Struct
    attribute :title, Types::String
    attribute :visible, Types::Bool
  end
end

rom = ROM.container(:sql, "sqlite::memory") do |conf|
  conf.default.create_table(:articles) do
    primary_key :id
    column :title, String, null: false
  end

  conf.relation(:articles) do
    schema(infer: true)
    auto_struct(true)

    def with_visible
      select_append { bool.cast(`TRUE`).as(:visible) }
    end
  end
end

rom.relations[:articles].insert(title: "Test title")

p rom.relations[:articles].with_visible.to_a # 'visible' is 1 on auto_struct
p rom.relations[:articles].with_visible.map_to(Structs::ArticleWithParamsBoolVisible).to_a # visible is true
# This fails (ideally should have visible as true)
# p rom.relations[:articles].with_visible.map_to(Structs::ArticleWithRegularBoolVisible).to_a

Expected behavior

I would expect that when I use bool.cast, I'd get a boolean back, regardless of which database is used. Even the result, with auto_struct set to true, I'd expect I'd get visible=true.

I'm not sure if this should be fixed in the casting code (as part of function) or implemented as an extension for SQLite.

A workaround that I found, shown above, is to use Types::Params::Bool, which maps 1 to true and 0 to false.

That works in this simple example, but in my app that's not working either. In fact, both Types::Bool and Types::Params::Bool "work" but instead of raising a Dry::Struct::Error, they just work with visible=1, in violation of the specified types that says they should be bools.

My environment

• Rom-sql 3.6, Rom 5.3

• Affects my production application: No

• Ruby version: 3.3

• OS: macOS 14.4.1

[flash-gordon]

"bool.cast(TRUE).as(:visible)" is a SQL statement, merely CAST(TRUE AS boolean) AS 'visible'. Setting the bool type does nothing on the casting side, it's on you. Sequel returns a string so it'll be a string. Same for all default types in rom-sql, they are nominal, with no typecasting for performance reasons.

[cllns]

Thanks @flash-gordon, that makes sense. That was a silly example since 'boolean' doesn't exist in SQLITE, but it's so permissive that it happens to work anyway. (and TRUE is an alias for 1).

My workaround for now is to override the initializer for my Struct with

def initialize(attributes)
  # Workaround for SQLite not having boolean type
  attributes[:visible] = attributes[:visible] == 1
  super
end

I guess the right way to do this is with a mapper?

[flash-gordon]

I guess the right way to do this is with a mapper?

Yes, but you can also replace the read type, it worked for me:

    def with_visible
      select_append {
        `TRUE`.cast(:boolean).as(:visible).meta(
          read: Types::Bool.constructor { _1.eql?(1) }
        )
      }
    end

[cllns]

Oh nice, thanks. That works for me too.

Do you think there could be room for a ROM plugin that does this SQLite boolean coercion? It'd be nice to abstract away this quirk so it doesn't have to be done every time.

[flash-gordon]

To do this, you need to swap the default :bool type with something. I don't know if this can be nicely done by a plugin. We have a dedicated namespace for Posgres' JSON(b) types: Types::PG::JSONB. We could have Types::SQLite::Bool but's not enough, we need a way to associate :bool with this particular type. I'll take a look into rom-sql's internals to see if it's possible to modify the type container for a relation.