Method new_from_constraints

datafusion/common/src/functional_dependencies.rs:199–232

Creates a new `FunctionalDependencies` object from the given constraints.

(
        constraints: Option<&Constraints>,
        n_field: usize,
    )

    /// Creates a new `FunctionalDependencies` object from the given constraints.
    pub fn new_from_constraints(
        constraints: Option<&Constraints>,
        n_field: usize,
    ) -> Self {
        if let Some(Constraints { inner: constraints }) = constraints {
            // Construct dependency objects based on each individual constraint:
            let dependencies = constraints
                .iter()
                .map(|constraint| {
                    // All the field indices are associated with the whole table
                    // since we are dealing with table level constraints:
                    let dependency = match constraint {
                        Constraint::PrimaryKey(indices) => FunctionalDependence::new(
                            indices.to_vec(),
                            (0..n_field).collect::<Vec<_>>(),
                            false,
                        ),
                        Constraint::Unique(indices) => FunctionalDependence::new(
                            indices.to_vec(),
                            (0..n_field).collect::<Vec<_>>(),
                            true,
                        ),
                    };
                    // As primary keys are guaranteed to be unique, set the
                    // functional dependency mode to `Dependency::Single`:
                    dependency.with_mode(Dependency::Single)
                })
                .collect::<Vec<_>>();
            Self::new(dependencies)
        } else {
            // There is no constraint, return an empty object:
            Self::empty()
        }
    }

    pub fn with_dependency(mut self, mode: Dependency) -> Self {
        self.deps.iter_mut().for_each(|item| item.mode = mode);