A table's scanInterval is not saved, so only the declaring thread uses it #4241

Summary

A table's scanInterval is validated when a declaration names it, but it is not saved on the catalog row. Only the thread that declared it uses it; threads that load the table from the catalog, and the declaring thread after a restart until its declaration runs again, scan at the derived cadence ((expiration + eviction) / 4).

Mechanism

• persistTableSettings in resources/databases.ts writes and clears expiration and eviction, not scanInterval.
• setTTLExpiration's object form replaces scanInterval with whatever the declaration passed, so a re-declaration that omits it resets it to the derived cadence on that thread.

For a schema-declared table this is mostly invisible, since every worker declares the table at startup. It shows for tables created at runtime (create_table does not take scanInterval) and for tables whose declaration runs on one thread only. Noted as accepted on #2831; filed so the decision is tracked.

Expected

Either save scanInterval with the other TTL settings (and adopt it like them), or document it as a per-declaration setting.

Review-Deferral: 0e0e0e216a2a71a6 severity=nit category=maintainability

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