marvinlanhenke commented on code in PR #309:
URL: https://github.com/apache/iceberg-rust/pull/309#discussion_r1553275061
##########
crates/iceberg/src/spec/transform.rs:
##########
@@ -261,6 +269,323 @@ impl Transform {
_ => self == other,
}
}
+
+ /// Projects a given predicate according to the transformation
+ /// specified by the `Transform` instance.
+ ///
+ /// This allows predicates to be effectively applied to data
+ /// that has undergone transformation, enabling efficient querying
+ /// and filtering based on the original, untransformed data.
+ ///
+ /// # Example
+ /// Suppose, we have row filter `a = 10`, and a partition spec
+ /// `bucket(a, 37) as bs`, if one row matches `a = 10`, then its partition
+ /// value should match `bucket(10, 37) as bs`, and we project `a = 10` to
+ /// `bs = bucket(10, 37)`
+ pub fn project(&self, name: String, predicate: &BoundPredicate) ->
Result<Option<Predicate>> {
+ let func = create_transform_function(self)?;
+
+ match self {
+ Transform::Identity => match predicate {
+ BoundPredicate::Unary(expr) => Self::project_unary(expr.op(),
name),
+ BoundPredicate::Binary(expr) =>
Ok(Some(Predicate::Binary(BinaryExpression::new(
+ expr.op(),
+ Reference::new(name),
+ expr.literal().to_owned(),
+ )))),
+ BoundPredicate::Set(expr) =>
Ok(Some(Predicate::Set(SetExpression::new(
+ expr.op(),
+ Reference::new(name),
+ expr.literals().to_owned(),
+ )))),
+ _ => Ok(None),
+ },
+ Transform::Bucket(_) => match predicate {
+ BoundPredicate::Unary(expr) => Self::project_unary(expr.op(),
name),
+ BoundPredicate::Binary(expr) => self.project_binary(name,
expr, &func),
+ BoundPredicate::Set(expr) => self.project_set(expr, name,
&func),
+ _ => Ok(None),
+ },
+ Transform::Truncate(width) => match predicate {
+ BoundPredicate::Unary(expr) => Self::project_unary(expr.op(),
name),
+ BoundPredicate::Binary(expr) => {
+ self.project_binary_with_adjusted_boundary(name, expr,
&func, Some(*width))
+ }
+ BoundPredicate::Set(expr) => self.project_set(expr, name,
&func),
+ _ => Ok(None),
+ },
+ Transform::Year | Transform::Month | Transform::Day |
Transform::Hour => {
+ match predicate {
+ BoundPredicate::Unary(expr) =>
Self::project_unary(expr.op(), name),
+ BoundPredicate::Binary(expr) => {
+ self.project_binary_with_adjusted_boundary(name, expr,
&func, None)
+ }
+ BoundPredicate::Set(expr) => self.project_set(expr, name,
&func),
+ _ => Ok(None),
+ }
+ }
+ _ => Ok(None),
+ }
+ }
+
+ /// Check if `Transform` is applicable on datum's `PrimitiveType`
+ fn can_transform(&self, datum: &Datum) -> bool {
+ let input_type = datum.data_type().clone();
+ self.result_type(&Type::Primitive(input_type)).is_ok()
+ }
+
+ /// Creates a unary predicate from a given operator and a reference name.
+ fn project_unary(op: PredicateOperator, name: String) ->
Result<Option<Predicate>> {
+ Ok(Some(Predicate::Unary(UnaryExpression::new(
+ op,
+ Reference::new(name),
+ ))))
+ }
+
+ /// Attempts to create a binary predicate based on a binary expression,
+ /// if applicable.
+ ///
+ /// This method evaluates a given binary expression and, if the operation
+ /// is equality (`Eq`) and the literal can be transformed, constructs a
+ /// `Predicate::Binary`variant representing the binary operation.
+ fn project_binary<T>(
Review Comment:
I missed that, we don't need a Generic. Fixed it.
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