Function parse_join_equivalences

src/expr-parser/src/parser.rs:1186–1217

(input: ParseStream)

    }

    pub fn parse_join_equivalences(input: ParseStream) -> syn::Result<Vec<Vec<MirScalarExpr>>> {
        let mut equivalences = vec![];
        while !input.is_empty() {
            let mut equivalence = vec![];
            loop {
                let mut worklist = vec![parse_operand(input)?];
                while let Some(operand) = worklist.pop() {
                    // Be more lenient and support parenthesized equivalences,
                    // e.g. `... AND (x = u + v = z + 1) AND ...`.
                    if let MirScalarExpr::CallBinary {
                        func: BinaryFunc::Eq(_),
                        expr1,
                        expr2,
                    } = operand
                    {
                        // We reverse the order in the worklist in order to get
                        // the correct order in the equivalence class.
                        worklist.push(*expr2);
                        worklist.push(*expr1);
                    } else {
                        equivalence.push(operand);
                    }
                }
                if !input.eat(syn::Token![=]) {
                    break;
                }
            }
            equivalences.push(equivalence);
            input.eat(kw::AND);
        }
        Ok(equivalences)
    }
}

/// Support for parsing [mz_expr::AggregateExpr].