64 lines
2.1 KiB
Markdown
64 lines
2.1 KiB
Markdown
---
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title: Optimize RLS Policies for Performance
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impact: HIGH
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impactDescription: 5-10x faster RLS queries with proper patterns
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tags: rls, performance, security, optimization
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---
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## Optimize RLS Policies for Performance
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Poorly written RLS policies can cause severe performance issues. Use subqueries and indexes strategically.
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**Incorrect (function called for every row):**
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```sql
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create policy orders_policy on orders
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using (auth.uid() = user_id); -- auth.uid() called per row!
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-- With 1M rows, auth.uid() is called 1M times
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```
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**Correct (wrap functions in SELECT):**
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```sql
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create policy orders_policy on orders
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using ((select auth.uid()) = user_id); -- Called once, cached
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-- 100x+ faster on large tables
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```
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Use security definer functions for complex checks:
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`SECURITY DEFINER` functions run with the creator's privileges and bypass RLS on any tables they touch — which is what makes them useful for internal lookups, but also what makes them dangerous if misused. Always include an explicit `auth.uid()` check inside the function body, keep them in a non-exposed schema, and revoke `EXECUTE` from any role that shouldn't call them directly.
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```sql
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-- Create helper function in a private schema
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create or replace function private.is_team_member(team_id bigint)
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returns boolean
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language sql
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security definer
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set search_path = ''
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as $$
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select exists (
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select 1 from public.team_members
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-- always check the calling user's identity inside the function
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where team_id = $1 and user_id = (select auth.uid())
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);
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$$;
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-- Revoke direct execution from public roles
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revoke execute on function private.is_team_member(bigint) from PUBLIC, anon, authenticated, service_role;
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-- Use in policy (indexed lookup, not per-row check)
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create policy team_orders_policy on orders
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using ((select private.is_team_member(team_id)));
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```
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Always add indexes on columns used in RLS policies:
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```sql
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create index orders_user_id_idx on orders (user_id);
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```
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Reference: [RLS Performance](https://supabase.com/docs/guides/database/postgres/row-level-security#rls-performance-recommendations)
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