Null Strategy Design

Design decisions around null value handling.

Null Representation

Metric Engine uses:

None for missing values
NaN for invalid calculations
Custom Null type for typed nulls

Strategy Pattern

class NullStrategy:
    def handle_null(self, value, context):
        raise NotImplementedError

class RaiseStrategy(NullStrategy):
    def handle_null(self, value, context):
        raise NullValueError()

class SkipStrategy(NullStrategy):
    def handle_null(self, value, context):
        return SKIP_MARKER

Integration Points

Input validation
Calculation operations
Output formatting
Aggregation functions

Trade-offs

Performance: Null checks add overhead
Safety: Explicit null handling prevents errors
Usability: Different strategies for different use cases