Data Derives (ORM Emission)

With this crate’s derive feature on, better-duck-core’s data derives are re-exported from better_duck_diesel with Diesel FromSql/ToSql emission enabled. The same Rust type that maps to a DuckDB ENUM or STRUCT in core then also binds and loads through a DuckDbConnection at its sql_types::DuckEnum / sql_types::DuckStruct column type.

What the feature does

The core derives (DuckEnum, DuckStruct, FromRow, ToRow) always exist in core. Turning on better-duck-diesel/derive makes DuckEnum and DuckStruct additionally emit Diesel ToSql / FromSql impls against better_duck_diesel::sql_types::DuckEnum / DuckStruct. Mechanically this flips on core’s derive-diesel feature, whose generated code resolves ::better_duck_diesel in your crate — so core itself never gains a Diesel dependency. See core feature flags.

The ORM path for these DuckDB-specific types is sql_query + QueryableByName (not the plain Queryable builder), because the Duck* SQL types have no Queryable blanket impl — see Type mapping.

Mapping an enum to `ENUM`

use better_duck_diesel::{DuckDbConnection, DuckEnum};
use better_duck_diesel::sql_types::DuckEnum as DuckEnumSql;
use diesel::prelude::*;
use diesel::sql_types::Integer;

#[derive(DuckEnum, Debug, PartialEq, Clone, Copy)]
enum Priority { Low, High }

#[derive(QueryableByName, Debug, PartialEq)]
struct Row {
    #[diesel(sql_type = Integer)]      id: i32,
    #[diesel(sql_type = DuckEnumSql)]  p: Priority,
}

// bind (ToSql)
diesel::sql_query("INSERT INTO tasks VALUES (1, $1)")
    .bind::<DuckEnumSql, _>(Priority::High)
    .execute(&mut conn)?;

// read (FromSql via QueryableByName)
let rows: Vec<Row> =
    diesel::sql_query("SELECT id, p FROM tasks ORDER BY id").get_results(&mut conn)?;

Mapping a struct to `STRUCT`

#[derive(DuckStruct)] works the same way at sql_types::DuckStruct — bind with .bind::<DuckStructSql, _>(value) and read via a QueryableByName field typed #[diesel(sql_type = DuckStructSql)].

Renaming

Field/variant renaming honors #[duck(rename = "…")] / #[duck(rename_all = "…")] (and the #[duck_enum(...)] forms for enums), identical to the core derives. The full casing list and resolution order are on the data derives page.

Re-exports

Available from better_duck_diesel under the derive feature: FromRow, ToRow, DuckEnum, DuckStruct.

FromRow / ToRow are the core driver’s row traits, not Diesel’s Queryable/Insertable. For ordinary standard-typed tables use Diesel’s own derives (see Schema); use DuckEnum / DuckStruct here specifically for the DuckDB ENUM / STRUCT column types. Without the derive feature, the derives still exist in core but don’t emit the Diesel FromSql/ToSql impls.

Data derives (core)

Authoring DuckEnum / DuckStruct and renaming rules.

Type mapping

The DuckEnum / DuckStruct SQL types.

Schema

Declaring the columns these types back.

Feature flags

How derive relates to core’s derive-diesel.

Getting Started

CRUD

DuckDB SQL DSL

Types & Pooling

Data Derives (ORM Emission)

What the feature does

Mapping an enum to `ENUM`

Mapping a struct to `STRUCT`

Renaming

Re-exports

See also

Data derives (core)

Type mapping

Schema

Feature flags

​What the feature does

​Mapping an enum to ENUM

​Mapping a struct to STRUCT

​Renaming

​Re-exports

​See also

Data derives (core)

Type mapping

Schema

Feature flags

What the feature does

Mapping an enum to `ENUM`

Mapping a struct to `STRUCT`

Renaming

Re-exports

See also