SetDifference / List Layer

Compute the set difference between two variable-length lists (left - right). Returns a list containing elements that exist in the left list but not in the right list. Similar to Python's set difference operation (set(a) - set(b)).

Mathematical definition: For sets A and B, the set difference A \ B (or A - B) is defined as: $A ∖ B = {x \in A ∣ x \in / B}$ In other words, elements that are in A but not in B.

Example transformation:

left_list	right_list	difference
[1, 2, 3, 4]	[2, 4, 5]	[1, 3]
[a, b, c]	[b, d]	[a, c]
[1, 1, 2, 3]	[1, 2]	[3]
[x, y]	[]	[x, y]
[]	[1, 2]	[]
[1, null, 3]	[1, 2]	[3]

Properties:

Not commutative: $A ∖ B \neq = B ∖ A$
Set difference with empty set: $A ∖ \emptyset = A$
Empty set difference: $\emptyset ∖ A = \emptyset$

Common applications:

Finding removed items between versions
Identifying unique user permissions
Analyzing set complement operations
Finding unmatched elements
Detecting missing features
Computing relative complements

Note: Duplicates in input lists are removed (set semantics). Null values are ignored. Order of elements in result is not guaranteed. Lists can have different lengths.

Table

SelectLeft

column

The left list column (SelectLeft) for set difference. Examples:

Current features: [f1, f2, f3, f4]
User permissions: [read, write, admin]
Product categories: [food, electronics, books] Lists can have different lengths. Duplicates allowed but treated as single elements.

SelectRight

column

The right list column (SelectRight) to subtract. Examples:

Removed features: [f2, f4]
Revoked permissions: [admin]
Discontinued categories: [books] Lists can have different lengths. Duplicates allowed but treated as single elements.

AsColumn

name

Name for the new column. If not provided, the system generates a unique name. If AsColumn matches an existing column, the existing column is replaced. The name should follow valid column naming conventions.