refactor: hoist null-propagating validity into a vortex-array helper

Promote the "result is null iff any operand is null" validity — previously
geo's binary_result_validity plus four inline copies in vortex-tensor — into a
shared helper, vortex_array::expr::null_propagating_validity. It conjoins every
child's validity, so it covers unary (l2_norm) and binary kernels alike.

- vortex-array: add expr::null_propagating_validity
- vortex-geo: GeoDistance / GeoContains / GeoIntersects use it; drop the local
  binary_result_validity
- vortex-tensor: InnerProduct / CosineSimilarity / L2Denorm / L2Norm use it
  instead of inlining and(child validities)

Signed-off-by: Nemo Yu <zyu379@wisc.edu>

Author: HarukiMoriarty

vortex-array/src/expr/exprs.rs

@@ -7,6 +7,7 @@ use std::sync::Arc;
 use std::sync::LazyLock;
 
 use vortex_error::VortexExpect;
+use vortex_error::VortexResult;
 use vortex_error::vortex_panic;
 use vortex_utils::iter::ReduceBalancedIterExt;
 
@@ -434,6 +435,22 @@ where
     iter.into_iter().reduce_balanced(and)
 }
 
+/// The validity of a scalar function whose result is null exactly when any operand is null: the
+/// conjunction of its children's validities.
+///
+/// This is the `ScalarFnVTable::validity` for kernels that propagate nulls and never produce a
+/// null from non-null inputs (comparisons, arithmetic, most geo and tensor ops). Returning it lets
+/// the planner derive the output's null mask without executing the kernel. Yields `None` when the
+/// expression has no children.
+pub fn null_propagating_validity(expression: &Expression) -> VortexResult<Option<Expression>> {
+    let child_validities = expression
+        .children()
+        .iter()
+        .map(Expression::validity)
+        .collect::<VortexResult<Vec<_>>>()?;
+    Ok(and_collect(child_validities))
+}
+
 /// Create a new [`Binary`] using the [`Add`](Operator::Add) operator.
 ///
 /// ## Example usage

vortex-geo/src/scalar_fn/contains.rs

@@ -10,6 +10,7 @@ use vortex_array::arrays::ScalarFnArray;
 use vortex_array::dtype::DType;
 use vortex_array::dtype::Nullability;
 use vortex_array::expr::Expression;
+use vortex_array::expr::null_propagating_validity;
 use vortex_array::scalar_fn::Arity;
 use vortex_array::scalar_fn::ChildName;
 use vortex_array::scalar_fn::EmptyOptions;
@@ -22,7 +23,6 @@ use vortex_session::VortexSession;
 use vortex_session::registry::CachedId;
 
 use crate::extension::validate_geometry_operands;
-use crate::scalar_fn::null_propagate::binary_result_validity;
 use crate::scalar_fn::null_propagate::execute_null_propagating;
 
 /// OGC `ST_Contains` between two native geometry operands, each a column or a constant
@@ -93,7 +93,7 @@ impl ScalarFnVTable for GeoContains {
         _: &Self::Options,
         expression: &Expression,
     ) -> VortexResult<Option<Expression>> {
-        binary_result_validity(expression)
+        null_propagating_validity(expression)
     }
 
     fn is_null_sensitive(&self, _: &Self::Options) -> bool {

vortex-geo/src/scalar_fn/distance.rs

@@ -12,6 +12,7 @@ use vortex_array::dtype::DType;
 use vortex_array::dtype::Nullability;
 use vortex_array::dtype::PType;
 use vortex_array::expr::Expression;
+use vortex_array::expr::null_propagating_validity;
 use vortex_array::scalar_fn::Arity;
 use vortex_array::scalar_fn::ChildName;
 use vortex_array::scalar_fn::EmptyOptions;
@@ -24,7 +25,6 @@ use vortex_session::VortexSession;
 use vortex_session::registry::CachedId;
 
 use crate::extension::validate_geometry_operands;
-use crate::scalar_fn::null_propagate::binary_result_validity;
 use crate::scalar_fn::null_propagate::execute_null_propagating;
 
 /// Planar (Euclidean) `ST_Distance` (no geodesic correction) between two native geometry
@@ -93,7 +93,7 @@ impl ScalarFnVTable for GeoDistance {
         _: &Self::Options,
         expression: &Expression,
     ) -> VortexResult<Option<Expression>> {
-        binary_result_validity(expression)
+        null_propagating_validity(expression)
     }
 
     fn is_null_sensitive(&self, _: &Self::Options) -> bool {

vortex-geo/src/scalar_fn/intersects.rs

@@ -10,6 +10,7 @@ use vortex_array::arrays::ScalarFnArray;
 use vortex_array::dtype::DType;
 use vortex_array::dtype::Nullability;
 use vortex_array::expr::Expression;
+use vortex_array::expr::null_propagating_validity;
 use vortex_array::scalar_fn::Arity;
 use vortex_array::scalar_fn::ChildName;
 use vortex_array::scalar_fn::EmptyOptions;
@@ -22,7 +23,6 @@ use vortex_session::VortexSession;
 use vortex_session::registry::CachedId;
 
 use crate::extension::validate_geometry_operands;
-use crate::scalar_fn::null_propagate::binary_result_validity;
 use crate::scalar_fn::null_propagate::execute_null_propagating;
 
 /// OGC `ST_Intersects` (not disjoint; boundary contact counts) between two native geometry
@@ -91,7 +91,7 @@ impl ScalarFnVTable for GeoIntersects {
         _: &Self::Options,
         expression: &Expression,
     ) -> VortexResult<Option<Expression>> {
-        binary_result_validity(expression)
+        null_propagating_validity(expression)
     }
 
     fn is_null_sensitive(&self, _: &Self::Options) -> bool {

vortex-geo/src/scalar_fn/null_propagate.rs

@@ -19,8 +19,6 @@ use vortex_array::arrays::PrimitiveArray;
 use vortex_array::dtype::DType;
 use vortex_array::dtype::Nullability;
 use vortex_array::dtype::PType;
-use vortex_array::expr::Expression;
-use vortex_array::expr::and;
 use vortex_array::scalar::Scalar;
 use vortex_array::validity::Validity;
 use vortex_buffer::BitBuffer;
@@ -132,16 +130,6 @@ fn all_null_array<T: GeoOutput>(len: usize) -> ArrayRef {
     ConstantArray::new(Scalar::null(T::null_dtype()), len).into_array()
 }
 
-/// The validity expression for a binary geo kernel: the result is null iff either operand is
-/// null. Returning this lets the planner derive the output's null mask symbolically (mask
-/// pushdown) instead of executing the whole kernel.
-pub(crate) fn binary_result_validity(expression: &Expression) -> VortexResult<Option<Expression>> {
-    Ok(Some(and(
-        expression.child(0).validity()?,
-        expression.child(1).validity()?,
-    )))
-}
-
 /// Run a binary geo kernel over operands `a` and `b`, each a column or a constant literal.
 ///
 /// The output is null wherever either operand is null, and its type is nullable if either operand

vortex-tensor/src/scalar_fns/cosine_similarity.rs

@@ -15,7 +15,7 @@ use vortex_array::arrays::scalar_fn::plugin::ScalarFnArrayVTable;
 use vortex_array::dtype::DType;
 use vortex_array::dtype::Nullability;
 use vortex_array::expr::Expression;
-use vortex_array::expr::and;
+use vortex_array::expr::null_propagating_validity;
 use vortex_array::match_each_float_ptype;
 use vortex_array::scalar_fn::Arity;
 use vortex_array::scalar_fn::ChildName;
@@ -180,10 +180,7 @@ impl ScalarFnVTable for CosineSimilarity {
         expression: &Expression,
     ) -> VortexResult<Option<Expression>> {
         // The result is null if either input tensor is null.
-        let lhs_validity = expression.child(0).validity()?;
-        let rhs_validity = expression.child(1).validity()?;
-
-        Ok(Some(and(lhs_validity, rhs_validity)))
+        null_propagating_validity(expression)
     }
 
     fn is_null_sensitive(&self, _options: &Self::Options) -> bool {

vortex-tensor/src/scalar_fns/inner_product.rs

@@ -18,7 +18,7 @@ use vortex_array::dtype::DType;
 use vortex_array::dtype::NativePType;
 use vortex_array::dtype::Nullability;
 use vortex_array::expr::Expression;
-use vortex_array::expr::and;
+use vortex_array::expr::null_propagating_validity;
 use vortex_array::match_each_float_ptype;
 use vortex_array::scalar_fn::Arity;
 use vortex_array::scalar_fn::ChildName;
@@ -164,10 +164,7 @@ impl ScalarFnVTable for InnerProduct {
         expression: &Expression,
     ) -> VortexResult<Option<Expression>> {
         // The result is null if either input tensor is null.
-        let lhs_validity = expression.child(0).validity()?;
-        let rhs_validity = expression.child(1).validity()?;
-
-        Ok(Some(and(lhs_validity, rhs_validity)))
+        null_propagating_validity(expression)
     }
 
     fn is_null_sensitive(&self, _options: &Self::Options) -> bool {

vortex-tensor/src/scalar_fns/l2_denorm.rs

@@ -31,7 +31,7 @@ use vortex_array::dtype::NativePType;
 use vortex_array::dtype::Nullability;
 use vortex_array::dtype::proto::dtype as pb;
 use vortex_array::expr::Expression;
-use vortex_array::expr::and;
+use vortex_array::expr::null_propagating_validity;
 use vortex_array::match_each_float_ptype;
 use vortex_array::scalar::Scalar;
 use vortex_array::scalar::ScalarValue;
@@ -256,10 +256,7 @@ impl ScalarFnVTable for L2Denorm {
         _options: &Self::Options,
         expression: &Expression,
     ) -> VortexResult<Option<Expression>> {
-        let normalized_validity = expression.child(0).validity()?;
-        let norms_validity = expression.child(1).validity()?;
-
-        Ok(Some(and(normalized_validity, norms_validity)))
+        null_propagating_validity(expression)
     }
 
     fn is_null_sensitive(&self, _options: &Self::Options) -> bool {

vortex-tensor/src/scalar_fns/l2_norm.rs

@@ -25,6 +25,7 @@ use vortex_array::dtype::NativePType;
 use vortex_array::dtype::Nullability;
 use vortex_array::dtype::proto::dtype as pb;
 use vortex_array::expr::Expression;
+use vortex_array::expr::null_propagating_validity;
 use vortex_array::match_each_float_ptype;
 use vortex_array::scalar::Scalar;
 use vortex_array::scalar_fn::Arity;
@@ -184,7 +185,7 @@ impl ScalarFnVTable for L2Norm {
         expression: &Expression,
     ) -> VortexResult<Option<Expression>> {
         // The result is null if the input tensor is null.
-        Ok(Some(expression.child(0).validity()?))
+        null_propagating_validity(expression)
     }
 
     fn is_null_sensitive(&self, _options: &Self::Options) -> bool {