Fokko commented on code in PR #6247:
URL: https://github.com/apache/iceberg/pull/6247#discussion_r1033226610


##########
python/pyiceberg/expressions/visitors.py:
##########
@@ -691,3 +692,68 @@ def manifest_evaluator(
     partition_schema = Schema(*partition_type.fields)
     evaluator = _ManifestEvalVisitor(partition_schema, partition_filter, 
case_sensitive)
     return evaluator.eval
+
+
+class ProjectionEvaluator(BooleanExpressionVisitor[BooleanExpression], ABC):
+    schema: Schema
+    spec: PartitionSpec
+    case_sensitive: bool
+
+    def __init__(self, schema: Schema, spec: PartitionSpec, case_sensitive: 
bool):
+        self.schema = schema
+        self.spec = spec
+        self.case_sensitive = case_sensitive
+
+    def project(self, expr: BooleanExpression) -> BooleanExpression:
+        #  projections assume that there are no NOT nodes in the expression 
tree. to ensure that this
+        #  is the case, the expression is rewritten to push all NOT nodes down 
to the expression
+        #  leaf nodes.
+        #  this is necessary to ensure that the default expression returned 
when a predicate can't be
+        #  projected is correct.
+        return rewrite_not(expr)
+
+    def visit_true(self) -> BooleanExpression:
+        return AlwaysTrue()
+
+    def visit_false(self) -> BooleanExpression:
+        return AlwaysFalse()
+
+    def visit_not(self, child_result: BooleanExpression) -> BooleanExpression:
+        raise NotImplementedError(f"Should not happen as the expression is 
rewritten: {child_result}")
+
+    def visit_and(self, left_result: BooleanExpression, right_result: 
BooleanExpression) -> BooleanExpression:
+        return And(left_result, right_result)
+
+    def visit_or(self, left_result: BooleanExpression, right_result: 
BooleanExpression) -> BooleanExpression:
+        return Or(left_result, right_result)
+
+    def visit_unbound_predicate(self, predicate: UnboundPredicate[L]) -> 
BooleanExpression:
+        partition_type = self.spec.partition_type(self.schema)
+        partition_schema = Schema(*partition_type.fields)
+        return predicate.bind(schema=partition_schema, 
case_sensitive=self.case_sensitive)

Review Comment:
   Ah, I see, I was missing this part: 
https://github.com/apache/iceberg/blob/master/api/src/main/java/org/apache/iceberg/expressions/Projections.java#L183-L185



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