ExpressionFilter
data class ExpressionFilter(val expression: AggregationExpression, val comparison: ComparisonOperator, val value: Double) : FilterExpression
Compares a computed expression, for example the hours from paidAt to shippedAt, with value. A record whose expression has no value (an operand is absent, or a division by zero) does not match, whatever the comparison. The expression is evaluated per record and cannot use an index, so the operator is expensive.