Parameterized Flows follow Brightway’s ParameterizedExchange index

The Parameters page Parameterized Flows table, recalculation, and Monte Carlo all use Brightway’s ParameterizedExchange index (activity-parameter group), not a scan of formula-bearing flows. A bwutils helper rebuilds that index for the written database on on_database_write when the database is small or already has parameters. Small means at most 1,000 outgoing flows. Skip databases above that cap that have no database/activity parameters; otherwise delete that database’s index rows, index every process that has a formula-bearing flow (dummy activity parameter if needed), then recalculate those groups. A database over the cap that already has parameters still gets a full pass. Single-flow formula edits stay on ExchangeModify. No one-shot backfill of existing projects.

Brightway Database.write sends on_database_write only when projects.dataset.is_sourced is true (default false), or when the caller passes signal=True. Excel import extra-sends that signal after bw2io writes with signals off. Database duplicate and BW25 migration pass signal=True so the same handler rebuilds the copy.

Considered Options

• Scan formula-bearing flows on every Parameters-page sync (shows flows that will not recalculate).
• Fill the index only on Excel import via bw2io activate_parameters (misses database-parameter-only processes and other writes).
• One-shot backfill of open projects (rejected: user rebuilds those by rewrite).