unwrap

Ruby

rel.unwrap([:attr])
rel.unwrap([:attr1, :attr2])

TypeScript

rel.unwrap('attr')

Problem

Flatten nested Hash/object attributes into top-level tuple attributes.

Example: I have tuples with nested address hashes, and I want to flatten them into individual columns.

Description

The unwrap operator takes tuples containing Hash/object-valued attributes and flattens them, promoting the nested keys to top-level attributes. This is the inverse of a wrap operation.

Given a tuple like { name: "Alice", address: { city: "London", country: "UK" } }, unwrapping the address attribute produces { name: "Alice", city: "London", country: "UK" }.

Ruby

Multiple attributes can be unwrapped in a single operation by passing an array of attribute names.

TypeScript

Pass the attribute name as a string to unwrap.

Requirements

The specified attributes must contain Hash/object values.

Examples

Basic unwrap

Ruby

wrapped = Bmg::Relation.new([
  { id: 1, name: "Alice", address: { city: "London", country: "UK" } },
  { id: 2, name: "Bob", address: { city: "Paris", country: "France" } },
  { id: 3, name: "Carol", address: { city: "Berlin", country: "Germany" } }
])

wrapped.unwrap([:address]).to_a

=>
[{:id=>1, :name=>"Alice", :city=>"London", :country=>"UK"},
 {:id=>2, :name=>"Bob", :city=>"Paris", :country=>"France"},
 {:id=>3, :name=>"Carol", :city=>"Berlin", :country=>"Germany"}]

TypeScript

const wrapped = Bmg([
  { id: 1, name: "Alice", address: { city: "London", country: "UK" } },
  { id: 2, name: "Bob", address: { city: "Paris", country: "France" } },
  { id: 3, name: "Carol", address: { city: "Berlin", country: "Germany" } }
])

wrapped.unwrap('address').toArray()

// =>
// [{ id: 1, name: "Alice", city: "London", country: "UK" },
//  { id: 2, name: "Bob", city: "Paris", country: "France" },
//  { id: 3, name: "Carol", city: "Berlin", country: "Germany" }]

Comparison with ungroup

unwrap and ungroup both flatten nested data, but they work differently:

Operator	Input	Output
unwrap	Hash/object attribute {a: {x: 1, y: 2}}	Flat tuple {x: 1, y: 2} (1 tuple out)
ungroup	Relation/array attribute {a: [{x: 1}, {x: 2}]}	Multiple tuples (N tuples out)

• Use unwrap for Hash/object attributes (one-to-one flattening)
• Use ungroup for Relation/array attributes (one-to-many flattening)