[erlang-bugs] mnesia:dirty_update_counter return ok instead of integer

[Anton Ryabkov]

Hello,

on Erlang R16B02 (also in previous versions) I've found that
mnesia:dirty_update_counter return 'ok' instead of integer when I
subscribed on detailed events for the "update counter's" table.

Example:

1> mnesia:start().
ok
2> mnesia:create_table(update_counter_table, [{ram_copies, [node()]},
{attributes, [key, counter]}]).
{atomic,ok}
3> mnesia:dirty_update_counter(update_counter_table, key1, 1).
1
4> mnesia:dirty_update_counter(update_counter_table, key1, 1).
2
5> mnesia:dirty_update_counter(update_counter_table, key1, 1).
3

6> mnesia:subscribe({table, update_counter_table, detailed}).
{ok,nonode@REDACTED}
7> mnesia:dirty_update_counter(update_counter_table, key2, 1).
ok
8> mnesia:dirty_update_counter(update_counter_table, key2, 1).
ok
9> mnesia:dirty_update_counter(update_counter_table, key2, 1).
ok

I have chaned code of mnesia and found that in mnesia_tm:1790 catched error
with reason:

{function_clause,
[{mnesia_subscr,what,
     [update_counter_table,
      {dirty,<0.33.0>},
      {update_counter_table,key1,10},
      write,
      [{update_counter_table,key1,9}]],
     [{file,"mnesia_subscr.erl"},{line,188}]},
 {mnesia_subscr,report_table_event,6,
     [{file,"mnesia_subscr.erl"},{line,172}]},
 {mnesia_tm,commit_update,6,
     [{file,"mnesia_tm.erl"},{line,1865}]},
 {mnesia_tm,do_update_op,3,
     [{file,"mnesia_tm.erl"},{line,1833}]},
 {mnesia_tm,do_update,4,[{file,"mnesia_tm.erl"},{line,1790}]},
 {mnesia_tm,do_commit,3,[{file,"mnesia_tm.erl"},{line,1782}]},
 {mnesia_tm,async_send_dirty,6,
     [{file,"mnesia_tm.erl"},{line,1994}]},
 {mnesia_tm,dirty,2,[{file,"mnesia_tm.erl"},{line,1077}]}]}.


The problem in the mnesia_subscr, It try prepare event for update_counter
like for write, but doesn't expect that Old row value may be NOT undefined
(like in case with update_counter).

Anton
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