# Ungroup

Inverse of group

## Signature

ungroup(operand: Relation, rva: AttrName) -> Relation

## Examples

ungroup(group(suppliers, [:city], :suppliers, allbut: true), :suppliers)

## Description

Computes the relation obtained by ungrouping a relation-valued attribute
`rva`. Ungrouping `rva` leads as many tuples as in `rva`, each extended
with the other attributes of `operand`.

`rva` must be a relation-valued attribute. It should not itself contain
any attribute whose name clashes with an attribute of `operand`.

## Implementation notes

This operator does not compile to SQL so far. Contributions are welcome
to provide it with a SQL compilation for SQL DBMSs that support this kind
of feature (e.g. PostgreSQL with JSON data type)