rdblue commented on code in PR #6437:
URL: https://github.com/apache/iceberg/pull/6437#discussion_r1050284725
##########
python/pyiceberg/expressions/visitors.py:
##########
@@ -753,3 +757,68 @@ def inclusive_projection(
schema: Schema, spec: PartitionSpec, case_sensitive: bool = True
) -> Callable[[BooleanExpression], BooleanExpression]:
return InclusiveProjection(schema, spec, case_sensitive).project
+
+
+class _ExpressionProjector(BooleanExpressionVisitor[BooleanExpression]):
+ """Rewrites a boolean expression by replacing unbound references with
references to fields in a struct schema
+
+ Args:
+ table_schema (Schema): The schema of the table
+ file_schema (Schema): The schema of the file
+ case_sensitive (bool): Whether to consider case when binding a reference
to a field in a schema, defaults to True
+
+ Raises:
+ TypeError: In the case a predicate is already bound
+ """
+
+ table_schema: Schema
+ file_schema: Schema
+ case_sensitive: bool
+
+ def __init__(self, table_schema: Schema, file_schema: Schema,
case_sensitive: bool) -> None:
+ self.table_schema = table_schema
+ self.file_schema = file_schema
+ self.case_sensitive = case_sensitive
+
+ def visit_true(self) -> BooleanExpression:
+ return AlwaysTrue()
+
+ def visit_false(self) -> BooleanExpression:
+ return AlwaysFalse()
+
+ def visit_not(self, child_result: BooleanExpression) -> BooleanExpression:
+ return Not(child=child_result)
+
+ def visit_and(self, left_result: BooleanExpression, right_result:
BooleanExpression) -> BooleanExpression:
+ return And(left=left_result, right=right_result)
+
+ def visit_or(self, left_result: BooleanExpression, right_result:
BooleanExpression) -> BooleanExpression:
+ return Or(left=left_result, right=right_result)
+
+ def visit_unbound_predicate(self, predicate: UnboundPredicate[L]) ->
BooleanExpression:
+ if not isinstance(predicate.term, Reference):
+ raise ValueError(f"Exprected reference: {predicate.term}")
+
+ field = self.table_schema.find_field(predicate.term.name,
case_sensitive=self.case_sensitive)
+ file_column_name = self.file_schema.find_column_name(field.field_id)
+
+ if not file_column_name:
+ raise ValueError(f"Not found in schema: {file_column_name}")
+
+ if isinstance(predicate, UnaryPredicate):
+ return predicate.__class__(Reference(file_column_name))
Review Comment:
Oh, nevermind. I see that the input expression is unbound. I'm not sure
whether it would be better to do this to a bound expression or not. That seems
like good separation of responsibilities and a good way to have consistent
error messages when an expression isn't valid for a particular schema.
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