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Add some documentation

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This commit is contained in:
gwenn 2015-12-20 19:27:28 +01:00
parent 83b9fd0aba
commit 987b06cf79
1 changed files with 16 additions and 7 deletions
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23
src/functions.rs
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@ -332,12 +332,16 @@ impl<'a> Context<'a> {
}
}
/// Aggregate is the callback interface for user-defined aggregate function.
///
/// `A` is the type of the aggregation context and `T` is the type of the final result.
/// Implementations should be stateless.
pub trait Aggregate<A, T> where T: ToResult {
/// Initializes the aggregation context.
fn init(&self) -> A; // TODO Validate: Fn(&Context)
fn init(&self) -> A;
/// "step" function called once for each row in an aggregate group.
fn step(&self, &mut Context, &mut A) -> Result<()>; // TODO Validate: Fn(&Context, A) -> A
/// Computes and sets the final result.
fn step(&self, &mut Context, &mut A) -> Result<()>;
/// Computes and returns the final result.
fn finalize(&self, &A) -> Result<T>;
}
@ -385,6 +389,11 @@ impl Connection {
self.db.borrow_mut().create_scalar_function(fn_name, n_arg, deterministic, x_func)
}
/// Attach a user-defined aggregate function to this database connection.
///
/// # Failure
///
/// Will return Err if the function could not be attached to the connection.
pub fn create_aggregate_function<A, D, T>(&self,
fn_name: &str,
n_arg: c_int,
@ -402,7 +411,7 @@ impl Connection {
/// Removes a user-defined function from this database connection.
///
/// `fn_name` and `n_arg` should match the name and number of arguments
/// given to `create_scalar_function`.
/// given to `create_scalar_function` or `create_aggregate_function`.
///
/// # Failure
///
@ -793,9 +802,9 @@ mod test {
.unwrap();
assert_eq!(4, result);
let single_sum = "SELECT my_sum(i), my_sum(j) FROM (SELECT 2 AS i, 1 AS j UNION ALL \
SELECT 2, 1)";
let result: (i64, i64) = db.query_row(single_sum, &[], |r| (r.get(0), r.get(1)))
let dual_sum = "SELECT my_sum(i), my_sum(j) FROM (SELECT 2 AS i, 1 AS j UNION ALL SELECT \
2, 1)";
let result: (i64, i64) = db.query_row(dual_sum, &[], |r| (r.get(0), r.get(1)))
.unwrap();
assert_eq!((4, 2), result);
}