Method try_merge

datafusion/physical-expr/src/projection.rs:373–382

Apply another projection on top of this projection, returning the combined projection. For example, if this projection is `SELECT c@2 AS x, b@1 AS y, a@0 as z` and the other projection is `SELECT x@0 + 1 AS c1, y@1 + z@2 as c2`, we return a projection equivalent to `SELECT c@2 + 1 AS c1, b@1 + a@0 as c2`. # Example ```rust use datafusion_common::{Result, ScalarValue}; use datafusion_expr::Operat

(&self, other: &ProjectionExprs)

    /// This function returns an error if any expression in the `other` projection cannot be
    /// applied on top of this projection.
    pub fn try_merge(&self, other: &ProjectionExprs) -> Result<ProjectionExprs> {
        let mut new_exprs = Vec::with_capacity(other.exprs.len());
        for proj_expr in other.exprs.iter() {
            new_exprs.push(ProjectionExpr {
                expr: self.unproject_expr(&proj_expr.expr)?,
                alias: proj_expr.alias.clone(),
            });
        }
        Ok(ProjectionExprs::new(new_exprs))
    }

    /// Extract the column indices used in this projection.
    /// For example, for a projection `SELECT a AS x, b + 1 AS y`, where `a` is at index 0 and `b` is at index 1,