Modify DELETE triggers to delete BEFORE instead of AFTER to prevent possible foreign key constraint violations

Signed-off-by: DL6ER <dl6er@dl6er.de>

advanced/Scripts/database_migration/gravity/18_to_19.sql

@@ -0,0 +1,27 @@
+.timeout 30000
+
+PRAGMA FOREIGN_KEYS=OFF;
+
+BEGIN TRANSACTION;
+
+DROP TRIGGER tr_domainlist_delete;
+CREATE TRIGGER tr_domainlist_delete BEFORE DELETE ON domainlist
+    BEGIN
+      DELETE FROM domainlist_by_group WHERE domainlist_id = OLD.id;
+    END;
+
+DROP TRIGGER tr_adlist_delete;
+CREATE TRIGGER tr_adlist_delete BEFORE DELETE ON adlist
+    BEGIN
+      DELETE FROM adlist_by_group WHERE adlist_id = OLD.id;
+    END;
+
+DROP TRIGGER tr_client_delete;
+CREATE TRIGGER tr_client_delete BEFORE DELETE ON client
+    BEGIN
+      DELETE FROM client_by_group WHERE client_id = OLD.id;
+    END;
+
+UPDATE info SET value = 19 WHERE property = 'version';
+
+COMMIT;