Row-Level Security in PostgreSQL: Control Data Access with Precision

Row-Level Security (RLS) isn’t an afterthought—it’s the line between control and exposure. In PostgreSQL, RLS lets you define access rules that filter rows per user or role. The server enforces these rules before the query result leaves memory. No duplicates, no leaks.

Manpages on RLS are terse. They tell you:

• Enable RLS with ALTER TABLE ... ENABLE ROW LEVEL SECURITY;
• Define policies using CREATE POLICY ... USING (condition);
• Attach policies to roles for precise control.

Start with enabling RLS on your table. Without this, policies do nothing. Then write policies that match your access pattern. For example:

ALTER TABLE accounts ENABLE ROW LEVEL SECURITY;

CREATE POLICY user_accounts
ON accounts
FOR SELECT
USING (owner_id = current_user_id());

Replace current_user_id() with the function or session variable that resolves the active user. The USING clause defines which rows they can see. You can also use WITH CHECK to control rows they can insert or update.

RLS logic lives in the database. This means your application code doesn’t need to repeat filtering. The database ensures all queries respect the same rules, even if a developer forgets a WHERE clause. This centralization is why RLS is critical for multi-tenant architectures, regulated datasets, and high-trust systems.

Manpages for RLS are direct, but they assume you already understand Postgres roles and privileges. RLS works alongside GRANT statements, but it is more fine-grained. If a role can SELECT, then RLS decides which rows they actually receive.

Test each policy. Run queries as different roles. Confirm no unauthorized rows appear. Misconfigured RLS can block valid access or silently allow leaks. Logs and EXPLAIN can help verify active policies.

When RLS is implemented well, security rules are immutable without explicit database changes. Unauthorized clients have no path to bypass them.

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