Function plan_function

src/sql/src/plan/query.rs:5429–5637

(
    ecx: &ExprContext,
    f @ Function {
        name,
        args,
        filter,
        over,
        distinct,
    }: &'a Function<Aug>,
)

}

fn plan_function<'a>(
    ecx: &ExprContext,
    f @ Function {
        name,
        args,
        filter,
        over,
        distinct,
    }: &'a Function<Aug>,
) -> Result<HirScalarExpr, PlanError> {
    let impls = match resolve_func(ecx, name, args)? {
        Func::Table(_) => {
            sql_bail!(
                "table functions are not allowed in {} (function {})",
                ecx.name,
                name
            );
        }
        Func::Scalar(impls) => {
            if over.is_some() {
                sql_bail!(
                    "OVER clause not allowed on {name}. The OVER clause can only be used with window functions (including aggregations)."
                );
            }
            impls
        }
        Func::ScalarWindow(impls) => {
            let (
                ignore_nulls,
                order_by_exprs,
                col_orders,
                _window_frame,
                partition_by,
                scalar_args,
            ) = plan_window_function_non_aggr(ecx, f)?;

            // All scalar window functions have 0 parameters. Let's print a nice error msg if the
            // user gave some args. (The below `func::select_impl` would fail anyway, but the error
            // msg there is less informative.)
            if !scalar_args.is_empty() {
                if let ResolvedItemName::Item {
                    full_name: FullItemName { item, .. },
                    ..
                } = name
                {
                    sql_bail!(
                        "function {} has 0 parameters, but was called with {}",
                        item,
                        scalar_args.len()
                    );
                }
            }

            // Note: the window frame doesn't affect scalar window funcs, but, strangely, we should
            // accept a window frame here without an error msg. (Postgres also does this.)
            // TODO: maybe we should give a notice

            let func = func::select_impl(ecx, FuncSpec::Func(name), impls, scalar_args, vec![])?;