Query Filters trong React Query là gì? Dùng ở đâu?

Query Filters là pattern matching system cho phép target nhóm queries khi thao tác hàng loạt.

• Dùng trong invalidateQueries, refetchQueries, removeQueries, cancelQueries.
• Filter options: queryKey (fuzzy match — ['todos'] match cả ['todos', 1]), type ('active' = đang có subscriber, 'inactive' = cached nhưng không ai dùng, 'all'), stale (true/false), fetchStatus ('fetching'/'paused'/'idle').

Ví dụ thực tế: user logout → queryClient.removeQueries({ type: 'all' }) xóa toàn bộ cache.

• Hoặc: mutation thành công → invalidateQueries({ queryKey: ['todos'], type: 'active' }) chỉ refetch todos đang hiển thị.

Query Filters are objects used to target specific queries when calling methods like invalidateQueries, cancelQueries, removeQueries, and refetchQueries.

• Filter properties: queryKey — partial or exact key matching; exact: true — only match queries with exactly this key; type — 'active' (has observers), 'inactive' (no observers), 'all'; stale — filter by stale state; predicate — function that receives a Query object and returns boolean for full custom filtering.
• Examples: queryClient.invalidateQueries({ queryKey: ['todos'] }) — invalidates all queries whose key starts with 'todos'; queryClient.invalidateQueries({ queryKey: ['todos'], exact: true }) — only invalidates ['todos'] exactly; queryClient.invalidateQueries({ type: 'active' }) — only refetches queries currently being observed.
• Filters are essential for targeted cache management after mutations.