Add database upgrade file 13.

Drops the old event tables.

NOTE: consider not applying this patch until confident that
the migration has proceeded smoothly. Dougal can operate just
fine without it.

etc/db/upgrades/upgrade13-v0.3.1-drop-old-event-tables.sql

@@ -0,0 +1,99 @@
+-- Drop old event tables.
+--
+-- New schema version: 0.3.1
+--
+-- ATTENTION:
+--
+-- ENSURE YOU HAVE BACKED UP THE DATABASE BEFORE RUNNING THIS SCRIPT.
+--
+--
+-- NOTE: This upgrade affects all schemas in the database.
+-- NOTE: Each application starts a transaction, which must be committed
+-- or rolled back.
+--
+-- This completes the migration from the old event logging mechanism by
+-- DROPPING THE OLD DATABASE OBJECTS, MAKING THE MIGRATION IRREVERSIBLE,
+-- other than by restoring from backup and manually transferring any new
+-- data that may have been created in the meanwhile.
+--
+-- To apply, run as the dougal user:
+--
+-- psql <<EOF
+-- \i $THIS_FILE
+-- COMMIT;
+-- EOF
+--
+-- NOTE: It can take a while if run on a large database.
+-- NOTE: It can be applied multiple times without ill effect.
+-- NOTE: This will lock the database while the transaction is active.
+--
+-- WARNING: Applying this upgrade drops the old tables. Ensure that you
+-- have migrated the data first.
+--
+-- NOTE: This is a patch version change so it does not require a
+-- backend restart.
+
+BEGIN;
+
+CREATE OR REPLACE PROCEDURE show_notice (notice text) AS $$
+BEGIN
+	RAISE NOTICE '%', notice;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE pg_temp.upgrade_survey_schema (schema_name text) AS $$
+BEGIN
+
+	RAISE NOTICE 'Updating schema %', schema_name;
+	-- We need to set the search path because some of the trigger
+	-- functions reference other tables in survey schemas assuming
+	-- they are in the search path.
+	EXECUTE format('SET search_path TO %I,public', schema_name);
+
+	DROP FUNCTION IF EXISTS
+		label_in_sequence(integer,text), reset_events_serials();
+
+	DROP VIEW IF EXISTS
+		events_midnight_shot, events_seq_timed, events_labels, "events";
+
+	DROP TABLE IF EXISTS
+		events_seq_labels, events_timed_labels, events_timed_seq, events_seq, events_timed;
+
+	DROP SEQUENCE IF EXISTS
+		events_seq_id_seq, events_timed_id_seq;
+
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE pg_temp.upgrade_database () AS $$
+DECLARE
+	row RECORD;
+BEGIN
+	FOR row IN
+		SELECT schema_name FROM information_schema.schemata
+		WHERE schema_name LIKE 'survey_%'
+		ORDER BY schema_name
+	LOOP
+		CALL pg_temp.upgrade_survey_schema(row.schema_name);
+	END LOOP;
+END;
+$$ LANGUAGE plpgsql;
+
+CALL pg_temp.upgrade_database();
+
+CALL show_notice('Cleaning up');
+DROP PROCEDURE pg_temp.upgrade_survey_schema (schema_name text);
+DROP PROCEDURE pg_temp.upgrade_database ();
+
+CALL show_notice('Updating db_schema version');
+INSERT INTO public.info VALUES ('version', '{"db_schema": "0.3.1"}')
+ON CONFLICT (key) DO UPDATE
+	SET value = public.info.value || '{"db_schema": "0.3.1"}' WHERE public.info.key = 'version';
+
+
+CALL show_notice('All done. You may now run "COMMIT;" to persist the changes');
+DROP PROCEDURE show_notice (notice text);
+
+--
+--NOTE Run `COMMIT;` now if all went well
+--