These are macro_rules! (declarative) macros exported at the crate root, carrying no extra
dependency. Two general helpers are always available; four more support
UDF bodies and need feature = "udf".
transaction!
transaction!(conn, { … }) runs a block inside a transaction, committing on Ok and rolling back
on Err or panic. The first argument is the connection variable (an identifier); it is
reborrowed and shadowed inside the block, so the block uses the same name.
It works with any connection exposing transaction(|c| -> Result<_, _>) — both the core
Connection and a Diesel DuckDbConnection — because it simply expands to
conn.transaction(|conn| { … }).
params!
params![a, b, …] builds a fixed-size array of &mut dyn AppendAble for
execute_with, so heterogeneous bind values don’t have to be
spelled out by hand.
It expands to [&mut a as &mut dyn AppendAble, …], so pass owned values (or
DuckValues, including DuckValue::Null). Because it yields an array, bind
it with &mut params![…].
transaction! and params! are part of the crate’s always-on surface — they do not require
the derive feature.
UDF body macros (feature = "udf")
These are only valid inside the relevant UDF function body; each panics if
called in the wrong context, but the panic is contained by the callback machinery and surfaces as a
normal query error (never UB).
duck_bail!
duck_bail!("message with {interpolation}") is return Err(format!(…).into()) for a fallible UDF
body — the surrounding error type must be From<String> (true for String and for the
Box<dyn Error + Send + Sync> that #[duckdb_scalar] / #[duckdb_table_function] route a
Result<T, E> through).
duck_state!
duck_state!(Type) returns a Clone of a #[duckdb_scalar(state(…))]
function’s shared state. Type must be Clone.
duck_projection! and duck_extra_info!
Inside a #[duckdb_table_function]
body:
duck_projection!() -> Vec<usize> — the 0-based column indices the current query needs (empty if
pushdown wasn’t requested; only valid under projection_pushdown).duck_extra_info!(Type) -> Type — a Clone of the registered extra_info value (Type: Clone).
See also
