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Support unbound transform in predicate expression #2456
Description
Is your feature request related to a problem or challenge?
Currently, only reference is supported in iceberg-rust's predicate API, which means we can construct scan filters like: ref(a) > 10), or ref(a) == 10 etc. However, for iceberg table with bucket transform, it's impossible to express the bucket partition filter, which should be something like bucket(10, col_a) >=0 and bucket(10, col_a) < 5. It would be useful to extend the predicate to support unbound transform in the predicate expression
Ref: the predicate enum definition
# in the predicate.rs
#[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
pub enum Predicate {
/// AlwaysTrue predicate, for example, `TRUE`.
AlwaysTrue,
/// AlwaysFalse predicate, for example, `FALSE`.
AlwaysFalse,
/// And predicate, for example, `a > 10 AND b < 20`.
And(LogicalExpression<Predicate, 2>),
/// Or predicate, for example, `a > 10 OR b < 20`.
Or(LogicalExpression<Predicate, 2>),
/// Not predicate, for example, `NOT (a > 10)`.
Not(LogicalExpression<Predicate, 1>),
/// Unary expression, for example, `a IS NULL`.
Unary(UnaryExpression<Reference>),
/// Binary expression, for example, `a > 10`.
Binary(BinaryExpression<Reference>),
/// Set predicates, for example, `a in (1, 2, 3)`.
Set(SetExpression<Reference>),
}Describe the solution you'd like
Add unbound transform to the predicate expression.
Willingness to contribute
I can contribute to this feature independently
Activity
advancedxy commentedon May 15, 2026
Hi @liurenjie1024 renjie, would you mind to take a look at this in your spare time. I can submit a PR if we can agree on this is the right direction.
TwinklerG commentedon Jun 8, 2026
I think it a great proposal. Happy to collaborate on this.