[erlang-questions] inconsistent results with fragmented table

[Noah Schwartz]

I have a table of type set that worked fine as a non-fragmented table. We
started seeing performance issues with the table and with the anticipation
of more clients in the system, we were worried the size would exceed the 2
GB max.

The table contains chat messages and we purge records older than 7 days.
There seem to be a number of keys that don't show up in a read activity
but, do show up when doing a table dump, a select, or using qlc to find
records. As such, when this purge policy runs records are found that when I
try to delete don't actually get deleted. It almost seems like read/delete
are working off of one set while qlc is working off of another set.

Code/outputs below. As you can see for a given key read returns nothing,
qlc returns an object, delete says it worked ok. Running the code again
gives the same results. Am I using the fragmentation API incorrectly
somehow?

Thanks in advance

*Code:*
-module(sel).
-include_lib("stdlib/include/qlc.hrl").
-record(archive_message313, {owner_with_day_utc, owner, with,
day_gregorian_seconds, messages = []}).
-export([run/0]).

run () ->
  Owner = {"9afa8671-7e88-436c-9ad4-4cb13ad45e1e", "dj.barker.xxx.com"},
  With = {"d735280e-d263-4e2b-beff-ed8ccaca5535", "dj.barker.xxx.com"},
  DayUtc = {2013, 6, 28},
  K = {Owner, With, DayUtc},

  DelFun = fun () -> mnesia:delete({archive_message313, K}) end,
  ReadFun = fun () -> mnesia:read({archive_message313, K}) end,

  QlcFun = fun () ->
    Q = qlc:q([M || M <- mnesia:table(archive_message313),
M#archive_message313.owner_with_day_utc == K]),
    qlc:eval(Q)
  end,

  Read = mnesia:activity(transaction, ReadFun, [], mnesia_frag),
  Qlc = mnesia:activity(transaction, QlcFun, [], mnesia_frag),
  Del = mnesia:activity(transaction, DelFun, [], mnesia_frag),

  {read_result, Read, qlc_result, Qlc, del_result, Del}.

*Output:*
{read_result,[],qlc_result,
             [{archive_message313,{{"9afa8671-7e88-436c-9ad4-4cb13ad45e1e",
                                    "dj.barker.xxx.com"},
                                   {"d735280e-d263-4e2b-beff-ed8ccaca5535",
                                    "dj.barker.xxx.com"},
                                   {2013,6,28}},
                                  {"9afa8671-7e88-436c-9ad4-4cb13ad45e1e",
                                   "dj.barker.xxx.com"},
                                  {"d735280e-d263-4e2b-beff-ed8ccaca5535",
                                   "dj.barker.xxx.com"},
                                  63539596800,
                                  [{{{2013,6,28},{13,36,34}},
                                    {xmlelement,"forwarded",

[{"xmlns","urn:xmpp:forward:0"}],
                                                [{xmlelement,"delay",

 [{"xmlns","urn:xmpp:delay"},

{"stamp","2013-06-28T13:36:34.000000Z"}],
                                                             []},
                                                 {xmlelement,"message",
                                                             [{"to",
                                                               "
9afa8671-7e88-436c-9ad4-4cb13ad45e1e@REDACTED"},
                                                              {"from",
                                                               "
d735280e-d263-4e2b-beff-ed8ccaca5535@REDACTED"},

{"type","chat"}],

 [{xmlelement,"body",[],[...]}]}]},
                                    1372426594.889164},
                                   {{{2013,6,28},{13,36,35}},
                                    {xmlelement,"forwarded",

[{"xmlns","urn:xmpp:forward:0"}],
                                                [{xmlelement,"delay",

 [{"xmlns","urn:xmpp:delay"},

{"stamp","2013-06-28T13:36:35.000000Z"}],
                                                             []},
                                                 {xmlelement,"message",
                                                             [{"to",
                                                               "
9afa8671-7e88-436c-9ad4-4cb13ad45e1e@REDACTED"},
                                                              {"from",
                                                               "
d735280e-d263-4e2b-beff-ed8ccaca5535@REDACTED"},

{"type",[...]}],

 [{xmlelement,"body",[],...}]}]},
                                    1372426595.124266},
                                   {{{2013,6,28},{13,36,35}},
                                    {xmlelement,"forwarded",

[{"xmlns","urn:xmpp:forward:0"}],
                                                [{xmlelement,"delay",

 [{"xmlns","urn:xmpp:delay"},

{"stamp","2013-06-28T13:36:35.000000Z"}],
                                                             []},
                                                 {xmlelement,"message",
                                                             [{"to",
                                                               "
9afa8671-7e88-436c-9ad4-4cb13ad45e1e@REDACTED"},

{"from",[...]},
                                                              {[...],...}],

 [{xmlelement,[...],...}]}]},
                                    1372426595.337535}]}],
             del_result,ok}
-- 
Noah
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