rdblue commented on code in PR #4815:
URL: https://github.com/apache/iceberg/pull/4815#discussion_r877596453
##########
python/src/iceberg/expressions/base.py:
##########
@@ -346,3 +346,116 @@ def bind(self, schema: Schema, case_sensitive: bool) ->
BoundReference:
raise ValueError(f"Cannot find field '{self.name}' in schema:
{schema}")
return BoundReference(field=field,
accessor=schema.accessor_for_field(field.field_id))
+
+
+class BooleanExpressionVisitor(ABC):
+ @abstractmethod
+ def visit_always_true(self) -> BooleanExpression:
+ """Visit method for an AlwaysTrue boolean expression
+
+ Note: This visit method has no arguments since AlwaysTrue instances
have no context.
+
+ Returns:
+ BooleanExpression: The resulting expression after any
modifications performed by the visitor
+ """
+
+ @abstractmethod
+ def visit_always_false(self) -> BooleanExpression:
+ """Visit method for an AlwaysFalse boolean expression
+
+ Note: This visit method has no arguments since AlwaysFalse instances
have no context.
+
+ Returns:
+ BooleanExpression: The resulting expression after any
modifications performed by the visitor
+ """
+
+ @abstractmethod
+ def visit_not(self, result: BooleanExpression) -> BooleanExpression:
+ """Visit method for a Not boolean expression
+
+ Args:
+ left (BooleanExpression): The left side of the expression
+ right (BooleanExpression): The right side of the expression
+
+ Returns:
+ BooleanExpression: The resulting expression after any
modifications performed by the visitor
+ """
+
+ @abstractmethod
+ def visit_and(self, left: BooleanExpression, right: BooleanExpression) ->
BooleanExpression:
+ """Visit method for an And boolean expression
+
+ Args:
+ left (BooleanExpression): The left side of the expression
+ right (BooleanExpression): The right side of the expression
+
+ Returns:
+ BooleanExpression: The resulting expression after any
modifications performed by the visitor
+ """
+
+ @abstractmethod
+ def visit_or(self, left: BooleanExpression, right: BooleanExpression) ->
BooleanExpression:
+ """Visit method for an Or boolean expression
+
+ Args:
+ left (BooleanExpression): The left side of the expression
+ right (BooleanExpression): The right side of the expression
+
+ Returns:
+ BooleanExpression: The resulting expression after any
modifications performed by the visitor
+ """
+
+ @abstractmethod
+ def visit_predicate(self, predicate):
+ """Visit method for a predicate in an expression tree
+
+ Args:
+ predicate (UnboundPredicate | BoundPredicate): An instance of
either an UnboundPredicate or a BoundPredicate,
+ depending on the concrete implementation.
+ """
+
+
+@singledispatch
+def visit(obj, visitor: BooleanExpressionVisitor) -> BooleanExpression:
+ """A generic function for applying a boolean expression visitor to any
point within an expression
+
+ The function traverses the expression in post-order fashion
+
+ Args:
+ obj(BooleanExpression): An instance of a BooleanExpression
+ visitor (BooleanExpressionVisitor): An instance of an implementation
of the generic BooleanExpressionVisitor base class
+
+ Raises:
+ NotImplementedError: If attempting to visit an unrecognized object type
+ """
+ raise NotImplementedError(f"Cannot visit non-type: {obj}")
+
+
[email protected](AlwaysTrue)
+def _(obj: AlwaysTrue, visitor: BooleanExpressionVisitor) -> BooleanExpression:
+ """Visit an AlwaysTrue boolean expression with a concrete
BooleanExpressionVisitor"""
+ return visitor.visit_always_true()
+
+
[email protected](AlwaysFalse)
+def _(obj: AlwaysFalse, visitor: BooleanExpressionVisitor) ->
BooleanExpression:
+ """Visit an AlwaysFalse boolean expression with a concrete
BooleanExpressionVisitor"""
+ return visitor.visit_always_true()
+
+
[email protected](Not)
+def _(obj: Not, visitor: BooleanExpressionVisitor) -> BooleanExpression:
+ """Visit a Not boolean expression with a concrete
BooleanExpressionVisitor"""
+ return visitor.visit_not(result=obj)
+
+
[email protected](And)
+def _(obj: And, visitor: BooleanExpressionVisitor) -> BooleanExpression:
+ """Visit a And boolean expression with a concrete
BooleanExpressionVisitor"""
+ return visitor.visit_and(left=obj.left, right=obj.right)
Review Comment:
Same here, this needs to visit the left and right operands.
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