Function plan_order_by_exprs

src/sql/src/plan/query.rs:2906–2927

Plans a slice of `ORDER BY` expressions. See `plan_order_by_or_distinct_expr` for details on the `output_columns` parameter. Returns the determined column orderings and a list of scalar expressions that must be mapped onto the underlying relation expression.

(
    ecx: &ExprContext,
    order_by_exprs: &[OrderByExpr<Aug>],
    output_columns: &[(usize, &ColumnName)],
)

/// Returns the determined column orderings and a list of scalar expressions
/// that must be mapped onto the underlying relation expression.
pub(crate) fn plan_order_by_exprs(
    ecx: &ExprContext,
    order_by_exprs: &[OrderByExpr<Aug>],
    output_columns: &[(usize, &ColumnName)],
) -> Result<(Vec<ColumnOrder>, Vec<HirScalarExpr>), PlanError> {
    let mut order_by = vec![];
    let mut map_exprs = vec![];
    for obe in order_by_exprs {
        let expr = plan_order_by_or_distinct_expr(ecx, &obe.expr, output_columns)?;
        // If the expression is a reference to an existing column,
        // do not introduce a new column to support it.
        let column = match expr {
            HirScalarExpr::Column(ColumnRef { level: 0, column }, _name) => column,
            _ => {
                map_exprs.push(expr);
                ecx.relation_type.arity() + map_exprs.len() - 1
            }
        };
        order_by.push(resolve_desc_and_nulls_last(obe, column));
    }
    Ok((order_by, map_exprs))
}

/// Plans an expression that appears in an `ORDER BY` or `DISTINCT ON` clause.
///