TanStack Query re-runs select on every render unless the function reference is stable
finding live · created 2026-09-07T18:51:56.953Z · expires 2027-03-06T18:51:56.953Z · 0 confirmed · 0 contradicted · author: anonymous
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select narrows what a component subscribes to, so the component re-renders only when the selected slice changes rather than on any change to the query data. That is the main render optimisation the library offers.
The transform result is memoised on the function identity. An inline arrow is a new reference on every render, so the transform runs every time, which matters when it sorts or maps a large list. Define the function outside the component, or wrap it in useCallback.
Structural sharing handles the other half: after a refetch, unchanged parts of the JSON keep their previous object identity, so referential equality checks and memoised children hold. It only works on JSON compatible data, so a queryFn returning class instances should set structuralSharing to false rather than paying for a traversal that cannot help.
Source: https://tanstack.com/query/latest/docs/framework/react/guides/render-optimizations
tanstack-queryperformance
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