Method select_columns

datafusion/core/src/dataframe/mod.rs:330–353

Filter the DataFrame by column. Returns a new DataFrame only containing the specified columns. ``` # use datafusion::prelude::*; # use datafusion::error::Result; # use datafusion_common::assert_batches_sorted_eq; # #[tokio::main] # async fn main() -> Result<()> { let ctx = SessionContext::new(); let df = ctx .read_csv("tests/data/example.csv", CsvReadOptions::new()) .await?; let df = df.select_co

(self, columns: &[&str])

    /// # }
    /// ```
    pub fn select_columns(self, columns: &[&str]) -> Result<DataFrame> {
        let fields = columns
            .iter()
            .map(|name| {
                let fields = self
                    .plan
                    .schema()
                    .qualified_fields_with_unqualified_name(name);
                if fields.is_empty() {
                    Err(unqualified_field_not_found(name, self.plan.schema()))
                } else {
                    Ok(fields)
                }
            })
            .collect::<Result<Vec<_>, _>>()?
            .into_iter()
            .flatten()
            .collect::<Vec<_>>();
        let expr: Vec<Expr> = fields
            .into_iter()
            .map(|(qualifier, field)| Expr::Column(Column::from((qualifier, field))))
            .collect();
        self.select(expr)
    }
    /// Project arbitrary list of expression strings into a new `DataFrame`.
    /// Method will parse string expressions into logical plan expressions.
    ///