DeltaControl

DeltaControl is a class that defines ways to handle null values during Delta updateBy operations, where Delta operations return the difference between the current row and the previous row.

Syntax

DeltaControl(value)

Parameters

ParameterTypeDescription
valueEnum

Defines how special cases should behave. When None, the default value is VALUE_DOMINATES. Enum options are:

  • DeltaControl.NULL_DOMINATES: A valid value following a null value returns null.
  • DeltaControl.VALUE_DOMINATES: A valid value following a null value returns the valid value.
  • DeltaControl.ZERO_DOMINATES: A valid value following a null value returns zero.

Returns

An instance of a DeltaControl class that can be used in an updateBy Delta operation.

Examples

The following example creates a newTable with three rows of int columns. Next, it creates three DeltaControl objects. Finally, it uses updateBy and invokes the Delta UpdateByOperation to demonstrate how the three Enum values for DeltaControl affect the output.

null_dominates = DeltaControl.NULL_DOMINATES
value_dominates = DeltaControl.VALUE_DOMINATES
zero_dominates = DeltaControl.ZERO_DOMINATES

source = newTable(
    intCol("X", 1, NULL_INT, 3, NULL_INT, 5, NULL_INT, NULL_INT, 8, 9),
    intCol("Y", 0, 5, 3, NULL_INT, NULL_INT, 3, 0, NULL_INT, 9),
    intCol("Z", 5, 6, 3, 4, 2, NULL_INT, 5, 0, 3)
)

result = source.updateBy([
    Delta(null_dominates, "X_null = X", "Y_null = Y", "Z_null = Z"),
    Delta(value_dominates, "X_value = X", "Y_value = Y", "Z_value = Z"),
    Delta(zero_dominates, "X_zero = X", "Y_zero = Y", "Z_zero = Z"),
])