Why can't I use two mutually exclusive Query at the same time.

[droog126]

What problem or need does this solve?

I have two instances of the same type, with children under each instance, I need to use

let mut parent_query=paramSet.p0();
let mut children_query=paramSet.p1();
for (children) in parent_query.iter_mut(){
  if  let OK (chilrenProps) in children_query.get_mut(children[0])
}

Why can't I use two mutually exclusive queries at the same time, this is unreasonable.
##What solution do you want?

To distinguish Entity such as ParentEntity childrenEntity type, we cannot guarantee that ordinary queries are mutually exclusive, but Parent and children may guarantee that these two are mutually exclusive queries.

##What alternatives have you considered?

Additional solutions to address and/or address the issues raised.

additional context

any other information you would like to add, such as relevant prior work,
Screenshots, benchmarks, and more

[alice-i-cecile]

Can you show the type signature of your system? Parents are commonly children themselves, in a nested hierarchy, so there's no guarantee that we're accessing distinct entities here.

A more general solution likely involves #3742, but for now, I would probably recommend using Query::get_many_mut.

[droog126]

 mut set: ParamSet<(
        Query<
            (
                &Children,
            ),
            With<SnakeTag>,
        >,
        Query<&mut Props, With<(Parent,SnakeChildrenTag)>>,
    )>,

almost so like this.

[droog126]

Can you show the type signature of your system? Parents are commonly children themselves, in a nested hierarchy, so there's no guarantee that we're accessing distinct entities here.

A more general solution likely involves #3742, but for now, I would probably recommend using Query::get_many_mut.

I learn form here https://bevy-cheatbook.github.io/features/parent-child.html.
Can a system have multiple queries at the same time?

[droog126]

in a way that conflicts with a previous system parameter. Consider using Without<T> to create disjoint Queries or merging conflicting Queries into a ParamSet,I seem to know what to do.

[easynam]

A system can have multiple queries - in your case, you can’t use both queries mutably at the same time because they're in a ParamSet together.

Since the queries don’t access any conflicting data (one accesses &Children and the other accesses &mut Props), you should be able to use 2 separate Query parameters instead, which will allow both to be used at the same time.