feat: dynamically create audit boilerplate

schema/000_audit_and_soft_delete.sql

@@ -0,0 +1,134 @@
+create type audited_column as (column_ text, type_ text);
+
+create function setup_audit_and_soft_delete( schema text
+                                           , table_ text
+                                           , tracked_columns audited_column[]
+                                           )
+  returns void
+  language plpgsql as $$
+  declare
+    col audited_column;
+    audit_table text := concat(schema, '.', table_, '_audit');
+    do_table_audit text := concat(schema, '.do_', table_, '_audit');
+    do_table_soft_delete text := concat(schema, '.do_', table_, '_soft_delete');
+    create_audit_table text := '';
+    create_do_table_audit text := '';
+    create_do_table_soft_delete text := '';
+    create_trigger_table_audit text := '';
+    create_trigger_table_soft_delete text := '';
+  begin
+   -- create table X_audit() >>>
+   create_audit_table := concat( create_audit_table
+                               , 'create table ', audit_table, E'\n'
+                               , '  ( ', table_, ' int not null references ', table_, '(id)', E'\n'
+                               , '  , kind public.audit_kind not null', E'\n'
+                               , '  , actor int not null references public.usr (id)', E'\n'
+                               );
+
+   foreach col in array tracked_columns loop
+     create_audit_table := concat( create_audit_table
+                                 , E'  , prev_', (col.column_), ' ', (col.type_), E' null\n'
+                                 );
+   end loop;
+
+   create_audit_table := concat( create_audit_table
+                               , '  );'
+                               );
+   -- <<< create table X_audit()
+
+   -- create function do_X_soft_delete() >>>
+   create_do_table_soft_delete := concat( create_do_table_soft_delete
+                                  , 'create function ', do_table_soft_delete, E'() returns trigger language plpgsql as \$\$\n'
+                                  , E'begin\n'
+                                  , E'  insert into ', audit_table, E'\n'
+                                  , E'    (', table_, E', kind, actor)\n'
+                                  , E'  values\n'
+                                  , E'    (OLD.id, \'delete\', 1);\n'
+                                  , E'\n'
+                                  , E'  update ', schema, '.', table_, E'\n'
+                                  , E'  set deleted = true\n'
+                                  , E'  where id = OLD.id;\n'
+                                  , E'\n'
+                                  , E'  return null;\n'
+                                  , E'end;\n'
+                                  , E'\$\$;'
+                                  );
+   -- <<< create function do_X_soft_delete()
+
+   -- create function do_X_audit() >>>
+   create_do_table_audit := concat( create_do_table_audit
+                                  , 'create function ', do_table_audit, E'() returns trigger language plpgsql as \$\$\n'
+                                  , E'declare\n'
+                                  , E'  audit_kind public.audit_kind;\n'
+                                  , E'  id int;\n'
+                                  );
+
+   foreach col in array tracked_columns loop
+     create_do_table_audit := concat( create_do_table_audit
+                                    , 'prev_', (col.column_), ' ', (col.type_), E';\n'
+                                    );
+   end loop;
+
+   create_do_table_audit := concat( create_do_table_audit
+                                  , E'begin\n'
+                                  , E'  if (TG_OP = \'INSERT\') then\n'
+                                  , E'    id := NEW.id;\n'
+                                  , E'    audit_kind := \'create\';\n'
+                                  , E'  elsif (TG_OP = \'UPDATE\') then\n'
+                                  , E'    id := OLD.id;\n'
+                                  , E'    audit_kind := \'modify\';\n'
+                                  );
+
+   foreach col in array tracked_columns loop
+     create_do_table_audit := concat( create_do_table_audit
+                                    , '    prev_', (col.column_), ' := OLD.', (col.column_), E';\n'
+                                    );
+   end loop;
+
+   create_do_table_audit := concat( create_do_table_audit
+                                  , E'  end if;\n'
+                                  , E'  insert into public.usr_audit\n'
+                                  , E'    (kind, usr, actor'
+                                  );
+
+   foreach col in array tracked_columns loop
+     create_do_table_audit := concat( create_do_table_audit
+                                    , ', prev_', (col.column_)
+                                    );
+   end loop;
+
+   create_do_table_audit := concat( create_do_table_audit
+                                  , E'  )\n'
+                                  , E'  values\n'
+                                  , E'    (audit_kind, id, 1'
+                                  );
+
+   foreach col in array tracked_columns loop
+     create_do_table_audit := concat( create_do_table_audit
+                                    , ', prev_', (col.column_)
+                                    );
+   end loop;
+
+   create_do_table_audit := concat( create_do_table_audit
+                                  , E');\n'
+                                  , E'  return NEW;\n'
+                                  , E'end;\n'
+                                  , E'\$\$;'
+                                  );
+   -- <<< create function do_X_audit()
+
+   create_trigger_table_audit := concat( 'create trigger trigger_', table_, E'_audit\n'
+                                       , 'after insert or update on ', schema, '.', table_, E'\n'
+                                       , 'for each row execute function ', do_table_audit, '();'
+                                       );
+   create_trigger_table_soft_delete := concat( 'create trigger trigger_', table_, E'_soft_delete\n'
+                                             , 'before delete on ', schema, '.', table_, E'\n'
+                                             , 'for each row execute function ', do_table_soft_delete, '();'
+                                             );
+   execute create_audit_table;
+   execute create_do_table_audit;
+   execute create_do_table_soft_delete;
+   execute create_trigger_table_audit;
+   execute create_trigger_table_soft_delete;
+  end;
+$$;

schema/000_newtype.sql

@@ -0,0 +1,16 @@
+create function create_newtype_text(qualified_name text)
+  returns void
+  language plpgsql
+  as $$
+begin
+  execute concat('create type ', qualified_name, ' as (str text);');
+  execute concat( 'create function '
+                , qualified_name || '_to_string(val ' || qualified_name || ')'
+                , E' returns text language sql as \'select (val.str);\';'
+                );
+  execute concat( 'create function '
+                , qualified_name || '_of_string(val text)'
+                , ' returns ' || qualified_name || E' language sql as \'select row(val);\';'
+                );
+end;
+$$;

schema/020_user.sql

@@ -1,87 +1,18 @@
-create type public.usr_username as (username text);
-
-create table public.usr_audit
-  ( usr           int                 not null
-  , kind          public.audit_kind   not null
-  , actor         int                 not null
-  , prev_username public.usr_username null
-  , prev_password public.hashed_text  null
-  , prev_email    public.email        null
-  );
+select create_newtype_text('public.usr_username');
 
 create table public.usr
   ( id       int                 not null primary key generated always as identity
   , uid      uuid                not null default gen_random_uuid()
   , deleted  boolean             not null default false
-  , username public.usr_username not null unique
+  , username public.usr_username not null
   , password public.hashed_text  not null
   , email    public.email        not null unique
   );
 
-alter table public.usr_audit
-  add constraint fk_usr_audit_usr
-  foreign key (usr)
-  references public.usr (id)
-, add constraint fk_usr_audit_actor
-  foreign key (actor)
-  references public.usr (id)
-;
-
-create function public.do_usr_audit()
-  returns trigger
-  language plpgsql as $$
-  declare
-    audit_kind public.audit_kind;
-    usr_id int;
-    prev_username public.usr_username := null;
-    prev_password public.hashed_text   := null;
-    prev_email    public.email         := null;
-  begin
-    if (TG_OP = 'UPDATE') then
-      usr_id := OLD.id;
-      audit_kind := 'modify';
-      prev_username := OLD.username;
-      prev_password := OLD.password;
-      prev_email := OLD.email;
-    elsif (TG_OP = 'INSERT') then
-      usr_id := NEW.id;
-      audit_kind := 'create';
-    end if;
-
-    insert into public.usr_audit
-      (kind, usr, actor, prev_username, prev_email, prev_password )
-    values
-      -- TODO actor
-      (audit_kind, usr_id, usr_id, prev_username, prev_email, prev_password );
-
-    return NEW;
-  end;
-$$;
-
-create function public.do_usr_soft_delete()
-  returns trigger
-  language plpgsql as $$
-  declare
-    audit_id int;
-  begin
-    insert into public.usr_audit
-      (kind, usr, actor)
-    values
-      -- TODO actor
-      ('delete' :: public.audit_kind, OLD.id, OLD.id);
-
-    update public.usr
-    set deleted = true
-    where id = OLD.id;
-
-    return null;
-  end;
-$$;
-
-create trigger trigger_usr_audit
-  after insert or update on public.usr
-  for each row execute function public.do_usr_audit();
-
-create trigger trigger_usr_soft_delete
-  before delete on public.usr
-  for each row execute function public.do_usr_soft_delete();
+select setup_audit_and_soft_delete( 'public'
+                                  , 'usr'
+                                  , array[ row('username', 'public.usr_username')
+                                         , row('password', 'public.hashed_text')
+                                         , row('email', 'public.email')
+                                         ] :: audited_column[]
+                                  );