Method project

datafusion/sql/src/select.rs:953–980

Wrap a plan in a projection

(
        &self,
        input: LogicalPlan,
        expr: Vec<SelectExpr>,
        set_expr_left_schema: Option<DFSchemaRef>,
    )

    /// Wrap a plan in a projection
    pub(crate) fn project(
        &self,
        input: LogicalPlan,
        expr: Vec<SelectExpr>,
        set_expr_left_schema: Option<DFSchemaRef>,
    ) -> Result<LogicalPlan> {
        // convert to Expr for validate_schema_satisfies_exprs
        let plain_exprs = expr
            .iter()
            .filter_map(|e| match e {
                SelectExpr::Expression(expr) => Some(expr.to_owned()),
                _ => None,
            })
            .collect::<Vec<_>>();
        self.validate_schema_satisfies_exprs(input.schema(), &plain_exprs)?;

        // When inside a set expression, pass the left-most schema so
        // that expressions get aliased to match, avoiding duplicate
        // name errors from expressions like `count(*), count(*)`.
        let builder = LogicalPlanBuilder::from(input);
        if let Some(left_schema) = set_expr_left_schema {
            builder
                .project_with_validation_and_schema(expr, &left_schema)?
                .build()
        } else {
            builder.project(expr)?.build()
        }
    }

    /// Create an aggregate plan.
    ///