Add database upgrade file 10.

NOTE: this is the first time we modify the actual data
in the database, as opposed to adding to the schema.

etc/db/upgrades/upgrade10-83be83e4→53ed096e-v0.2.0.sql

@@ -0,0 +1,84 @@
+-- Upgrade the database from commit 83be83e4 to 53ed096e.
+--
+-- New schema version: 0.2.0
+--
+-- 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 migrates the file hashes to address issue #173.
+-- The new hashes use size, modification time, creation time and the
+-- first half of the MD5 hex digest of the file's absolute path.
+--
+-- It's a minor (rather than patch) version number increment because
+-- changes to `bin/datastore.py` mean that the data is no longer
+-- compatible with the hashing function.
+--
+-- 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.
+
+
+BEGIN;
+
+CREATE OR REPLACE PROCEDURE show_notice (notice text) AS $$
+BEGIN
+	RAISE NOTICE '%', notice;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE migrate_hashes (schema_name text) AS $$
+BEGIN
+	RAISE NOTICE 'Migrating schema %', schema_name;
+	-- We need to set the search path because some of the trigger
+	-- functions reference other tables in survey schemas assuming
+	-- they are in the search path.
+	EXECUTE format('SET search_path TO %I,public', schema_name);
+	EXECUTE format('UPDATE %I.files SET hash = array_to_string(array_append(trim_array(string_to_array(hash, '':''), 1), left(md5(path), 16)), '':'')', schema_name);
+	EXECUTE 'SET search_path TO public'; -- Back to the default search path for good measure
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE upgrade_10 () AS $$
+DECLARE
+	row RECORD;
+BEGIN
+	FOR row IN
+		SELECT schema_name FROM information_schema.schemata
+		WHERE schema_name LIKE 'survey_%'
+		ORDER BY schema_name
+	LOOP
+		CALL migrate_hashes(row.schema_name);
+	END LOOP;
+END;
+$$ LANGUAGE plpgsql;
+
+CALL upgrade_10();
+
+CALL show_notice('Cleaning up');
+DROP PROCEDURE migrate_hashes (schema_name text);
+DROP PROCEDURE upgrade_10 ();
+
+CALL show_notice('Updating db_schema version');
+INSERT INTO public.info VALUES ('version', '{"db_schema": "0.2.0"}')
+ON CONFLICT (key) DO UPDATE
+	SET value = public.info.value || '{"db_schema": "0.2.0"}' 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
+--