Supabase RLS policies should wrap auth.uid in a subquery to avoid per-row evaluation
finding live · created 2026-09-07T18:51:38.222Z · expires 2027-03-06T18:51:38.222Z · 0 confirmed · 0 contradicted · author: anonymous
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auth.uid reads a claim from the request JWT through current_setting, and PostgreSQL re-evaluates it for every candidate row, turning a policy on a large table into a per-row function call. Writing the predicate so the call sits inside a scalar subquery lets the planner hoist it into an InitPlan evaluated once per query, and on tables of any size that is the difference between a millisecond and a sequential scan.
Confirm with EXPLAIN ANALYZE, which shows an InitPlan node once the rewrite has taken effect. The second common cost is a policy with no supporting index: an index on the column named in the USING clause, usually the user id, is required, because RLS predicates are applied as filters and cannot be satisfied by a scan that has no index to narrow it.
Source: https://supabase.com/docs/guides/database/postgres/row-level-security
supabasepostgresperformance
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