Expiring rows + cleanup — Examples

Expiring rows + cleanup

Give rows a time-to-live: hide them from reads once they expire, and delete them on a schedule. A policy filters expired rows out of SELECT; a @for function registers a pg_cron job to purge them.

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use extension 'pg_cron';
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type Session extends Base {
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  required token: str { constraint exclusive; };
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  expires_at: datetime;
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  policy hide_expired for select
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    using ( .expires_at is null or .expires_at >= now() );
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}
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@for Session
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function session_gc() -> int64 {
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  return cron.schedule('session-gc', '*/5 * * * *',
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    aql`delete Session filter .expires_at < now()`);
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};

The policy makes a query see only rows that are not yet expired (or have no expiry) — the app never has to add a WHERE expires_at >= now().
The sweep is written as inline AQL: it compiles to DELETE FROM "session" … while the migration is generated, so a rename in the type is caught at build time rather than silently breaking the cron job.
@for Session marks session_gc as a run-once setup function: Axel invokes it a single time (SELECT session_gc();) in the migration that first creates it, scheduling the cron job. See Functions → @for.
The cleanup job connects as a privileged role and bypasses RLS, so it can see and delete the expired rows the app can’t.

Reading is just a normal select — expired sessions are already invisible:

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select Session { id, token } filter .token = $token<str>;

From generated code

Saved as get_session.aql, the lookup returns the row or null — and an expired session reads as null because the policy has already filtered it out:

TypeScript
Go

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const session = await runner.query.getSession({ token }); // GetSessionRow | null
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if (!session) throw new Error("invalid or expired session");

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session, err := runner.Query.GetSession(ctx, gen.GetSessionParams{Token: token}) // *GetSessionRow
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if session == nil {
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    return errors.New("invalid or expired session")
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}