Function parse_top_k

src/expr-parser/src/parser.rs:529–585

(ctx: CtxRef, input: ParseStream)

    }

    fn parse_top_k(ctx: CtxRef, input: ParseStream) -> Result {
        let top_k = input.parse::<kw::TopK>()?;

        let group_key = if input.eat(kw::group_by) {
            input.parse::<syn::Token![=]>()?;
            let inner;
            syn::bracketed!(inner in input);
            inner.parse_comma_sep(scalar::parse_column_index)?
        } else {
            vec![]
        };

        let order_key = if input.eat(kw::order_by) {
            input.parse::<syn::Token![=]>()?;
            let inner;
            syn::bracketed!(inner in input);
            inner.parse_comma_sep(scalar::parse_column_order)?
        } else {
            vec![]
        };

        let limit = if input.eat(kw::limit) {
            input.parse::<syn::Token![=]>()?;
            Some(scalar::parse_expr(input)?)
        } else {
            None
        };

        let offset = if input.eat(kw::offset) {
            input.parse::<syn::Token![=]>()?;
            input.parse::<syn::LitInt>()?.base10_parse::<usize>()?
        } else {
            0
        };

        let monotonic = input.eat(kw::monotonic);

        let expected_group_size = if input.eat(kw::exp_group_size) {
            input.parse::<syn::Token![=]>()?;
            Some(input.parse::<syn::LitInt>()?.base10_parse::<u64>()?)
        } else {
            None
        };

        let parse_inputs = ParseChildren::new(input, top_k.span().start());
        let input = Box::new(parse_inputs.parse_one(ctx, parse_expr)?);

        Ok(MirRelationExpr::TopK {
            input,
            group_key,
            order_key,
            limit,
            offset,
            monotonic,
            expected_group_size,
        })
    }