mirror of
https://github.com/processone/ejabberd.git
synced 2024-11-22 16:20:52 +01:00
44 lines
1.7 KiB
Erlang
44 lines
1.7 KiB
Erlang
%% ``The contents of this file are subject to the Erlang Public License,
|
|
%% Version 1.1, (the "License"); you may not use this file except in
|
|
%% compliance with the License. You should have received a copy of the
|
|
%% Erlang Public License along with this software. If not, it can be
|
|
%% retrieved via the world wide web at http://www.erlang.org/.
|
|
%%
|
|
%% Software distributed under the License is distributed on an "AS IS"
|
|
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
|
|
%% the License for the specific language governing rights and limitations
|
|
%% under the License.
|
|
%%
|
|
%% The Initial Developer of the Original Code is ProcessOne.
|
|
%% Portions created by ProcessOne are Copyright 2006-2010, ProcessOne
|
|
%% All Rights Reserved.''
|
|
|
|
-module(p1_mnesia).
|
|
-author('mickael.remond@process-one.net').
|
|
|
|
-export([count_records/2]).
|
|
|
|
%% Return the number of records matching a given match expression.
|
|
%% This function is intended to be used inside a Mnesia transaction.
|
|
%% The count has been written to use the fewest possible memory by
|
|
%% getting the record by small increment and by using continuation.
|
|
-define(BATCHSIZE, 100).
|
|
count_records(Tab, MatchExpression) ->
|
|
%% the result contains list of [] for each match: We do not need
|
|
%% actual values as we only count the data.
|
|
case mnesia:select(Tab, [{MatchExpression, [], [[]]}], ?BATCHSIZE, read) of
|
|
{Result,Cont} ->
|
|
Count = length(Result),
|
|
count_records_cont(Cont, Count);
|
|
'$end_of_table' ->
|
|
0
|
|
end.
|
|
count_records_cont(Cont, Count) ->
|
|
case mnesia:select(Cont) of
|
|
{Result,Cont} ->
|
|
NewCount = Count + length(Result),
|
|
count_records_cont(Cont, NewCount);
|
|
'$end_of_table' ->
|
|
Count
|
|
end.
|