# Objective
`WorldQuery::Fetch` is a type used to optimize the implementation of
queries. These types are hidden and not intended to be outside of the
engine, so there is no need to provide type aliases to make it easier to
refer to them. If a user absolutely needs to refer to one of these
types, they can always just refer to the associated type directly.
## Solution
Deprecate these type aliases.
---
## Changelog
- Deprecated the type aliases `QueryFetch` and `ROQueryFetch`.
## Migration Guide
The type aliases `bevy_ecs::query::QueryFetch` and `ROQueryFetch` have
been deprecated. If you need to refer to a `WorldQuery` struct's fetch
type, refer to the associated type defined on `WorldQuery` directly:
```rust
// Before:
type MyFetch<'w> = QueryFetch<'w, MyQuery>;
type MyFetchReadOnly<'w> = ROQueryFetch<'w, MyQuery>;
// After:
type MyFetch<'w> = <MyQuery as WorldQuery>::Fetch;
type MyFetchReadOnly<'w> = <<MyQuery as WorldQuery>::ReadOnly as WorldQuery>::Fetch;
```
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