fix repeatable migrations

db/views/R__001_vw_modbus_last_verified.sql

@@ -0,0 +1,21 @@
+-- poslední úspěšně ověřený zápis per (site, asset, register)
+
+drop view if exists ems.vw_modbus_last_verified;
+
+create view ems.vw_modbus_last_verified as
+select distinct on (mc.site_id, mc.asset_type, mc.asset_id, mc.register)
+  mc.id,
+  mc.site_id,
+  mc.asset_type,
+  mc.asset_id,
+  mc.register,
+  mc.value_verified,
+  mc.verified_at,
+  mc.status
+from ems.modbus_command mc
+where mc.status = 'verified'
+  and mc.value_verified is not null
+order by mc.site_id, mc.asset_type, mc.asset_id, mc.register, mc.verified_at desc nulls last, mc.id desc;
+
+comment on view ems.vw_modbus_last_verified is
+  'DISTINCT ON (register) poslední verified řádek pro ověření / mapu registrů.';