Derive Macro QueryId

#[derive(QueryId)]

Implements QueryId

For example, given this struct:

#[derive(diesel::query_builder::QueryId)]
pub struct And<Left, Right> {
    left: Left,
    right: Right,
}

the following implementation will be generated

impl<Left, Right> QueryId for And<Left, Right>
where
    Left: QueryId,
    Right: QueryId,
{
    type QueryId = And<Left::QueryId, Right::QueryId>;

    const HAS_STATIC_QUERY_ID: bool = Left::HAS_STATIC_QUERY_ID && Right::HAS_STATIC_QUERY_ID;
}

If the SQL generated by a struct is not uniquely identifiable by its type, meaning that HAS_STATIC_QUERY_ID should always be false, you shouldn’t derive this trait. In that case, you should implement it manually instead.