sqlgen/docs/enum.md

Enums

Enums can directly be used in sqlgen structs. They are mapped to native enum types in PostgreSQL and MySQL. In sqlite, which does not support native enum types, they are stored as TEXT by default.

Usage

Basic Definition

enum class Color : int { RED = 1, GREEN = 2, BLUE = 3 };
struct Flower {
    sqlgen::PrimaryKey<std::string> name;
    Color color;
}

const auto red_rose = Flower{
    .name = "Rose",
    .color = Color::RED,
};

This generates the following SQL schema:

CREATE TYPE IF NOT EXISTS "Color" AS ENUM ('RED', 'GREEN', 'BLUE');
CREATE TABLE IF NOT EXISTS "Flower"(
    "name"  TEXT NOT NULL,
    "color" Color NOT NULL,
    PRIMARY_KEY("name")
);

Notes

• Due to naming restrictions in PostgreSQL, the namespace operator :: is replaced with __. Thus, an enum defined as namespace1::some_struct::MyEnum will be created in the database as namespace1__some_struct__MyEnum. This mangled name can at most be 63 characters long.
• Enums are specific types in PostgreSQL. They are only created once and shared between tables.
• In MySQL, enums are stored as native types but they are not shared between tables.
• In sqlite, enums are stored as TEXT by default. If you need to use integers, you can specialize the Parser<T> struct as explained here.
• You can use rfl::enum_to_string and rfl::string_to_enum to convert between enum values and their string representations.