Data migrations. A MIGRATION ['name'] FOR <trigger> <schema>.<table>.<member> AS $$…$$; block attaches raw SQL to a structural change (ADD COLUMN, ALTER COLUMN TYPE, or ADD CONSTRAINT) and is spliced into the plan only when the matching change is planned. A block matching nothing is reported as an informational diagnostic and is safe to delete.
Decomposed NOT NULL adds. A required column add with no default and a matching FOR ADD COLUMN migration is planned as add-nullable → run the migration SQL → SET NOT NULL, so the add succeeds against a populated table.
Hazard suppression. A matching migration block silences the corresponding data-hazard diagnostic (per trigger; unique-index hazards have no trigger and are never suppressed).
ExecuteDataMigration plan action carrying the spliced SQL. Executing a plan containing one requires a provider that recognizes it (4.3+); plans with no matched blocks are unaffected.
