Method project

src/expr/src/linear.rs:118–124

Retain only the indicated columns in the presented order.

(mut self, columns: I)

    /// Retain only the indicated columns in the presented order.
    pub fn project<I>(mut self, columns: I) -> Self
    where
        I: IntoIterator<Item = usize> + std::fmt::Debug,
    {
        self.projection = columns.into_iter().map(|c| self.projection[c]).collect();
        self
    }

    /// Retain only rows satisfying these predicates.
    ///