[mnesia]mnesia内存备份表存储数据总结

　　今天群里有一朋友(随波逐流磨剑)提了这么一个问题说并行写入时数据丢失，当然最后的原因是他没等所有写入进程执行完就进行查询，所以数据自然少了，不过这不是我要说的重点，重点是我在帮他测试程序的时候遇到了一个警告和一个错误：

警告：** WARNING ** Mnesia is overloaded: {mnesia_tm,  message_queue_len,   [2107,1441]}

错误：** Too many db tables **

 

代码：

-module(test_mnesia).
%%-include("test_mnesia.hrl").

-export([init/0,insert_recodes/2,select/0,select2/0,clear/0]).
-record(hdjsw, {id, bei_bao, ci_shu, fu_jian, jie_shu_date, sheng_cheng_date, shi_yong_date, bian_hao}).
-record(hdjoin, {id, hdjsw, name, type}).

init() ->

	%spawn(fun()-> randoms:start() end),

	case mnesia:create_schema([node()]) of
		ok ->
			ok;
		_ ->
			mnesia:delete_schema([node()]),
			mnesia:create_schema([node()])
	end,

	mnesia:start(),

	case mnesia:create_table(hdjsw,[{ram_copies, []},{type, bag},{attributes, record_info(fields,hdjsw)}]) of
	{atomic, ok} ->
	    ok;
	_Any1 ->
		mnesia:delete_table(hdjsw),
	    mnesia:create_table(hdjsw,[{ram_copies, []},{type, bag},{attributes, record_info(fields,hdjsw)}])
    end,
    
	case mnesia:create_table(hdjoin,[{ram_copies, []},{type, bag},{attributes, record_info(fields,hdjoin)}]) of
	{atomic, ok} ->
	    ok;
	_Any2 ->
		mnesia:delete_table(hdjoin),
	    mnesia:create_table(hdjoin,[{ram_copies, []},{type, bag},{attributes, record_info(fields,hdjoin)}])
    end.


%	mnesia:create_table(hdjsw,[{ram_copies, []},{attributes, record_info(fields,hdjsw)}]),
%	mnesia:create_table(hdjoin,[{ram_copies, []},{attributes, record_info(fields,hdjoin)}]).
	
insert_recodes(N,T) ->%200000,2000
	C = trunc(N/T),%100
	M = N rem T,%0
	case C of
	0 ->
		spawn_insert_recode(N,1);
	_ ->
		spawn_insert_recode(T,C),
		spawn_insert_recode(M,1)
	end.
	
spawn_insert_recode(0,_) ->
	ok;
spawn_insert_recode(N,M) ->%{2000, 100},{500,1}
		spawn(fun()-> insert_recode(M) end),
		spawn_insert_recode(N-1,M).
	
insert_recode(0) ->
	ok;
insert_recode(N) ->%10

	Hdjsw = #hdjsw{id=get_string(),
					bei_bao = "dsg",
					ci_shu = "asdhg",
					fu_jian = "adfsh",
					jie_shu_date = "sadhged",
					sheng_cheng_date = 44,
					shi_yong_date = "dsfh",
					bian_hao = 54},
	Fun = fun() ->
		mnesia:write(Hdjsw),
		insert(Hdjsw,10)
	end,
	%spawn(fun()-> mnesia:transaction(Fun) end),
	mnesia:transaction(Fun),
	insert_recode(N-1).
	
insert(_Hdjsw,0) ->
	ok;
insert(Hdjsw,N) ->
	Hdjoin = #hdjoin{
			id = get_string(),
			hdjsw = Hdjsw,
			name = hdjswname,
			type = 2
	},
	mnesia:write(Hdjoin),
	insert(Hdjsw,N-1).

select() ->
	F = fun() ->
		Q = #hdjsw{id = '$1', _ = '_'},
		mnesia:select(hdjsw, [{Q, [], ['$1']}])
	end,
	{atomic, L} = mnesia:transaction(F),
	length(L).
	
	
select2() ->
	F = fun() ->
		Q = #hdjoin{id = '$1', _ = '_'},
		mnesia:select(hdjoin, [{Q, [], ['$1']}])
	end,
	{atomic, L} = mnesia:transaction(F),
	length(L).
	
clear() ->
	mnesia:clear_table(hdjsw),
	mnesia:clear_table(hdjoin).
	
get_string() ->
    {M, S, L} = now(),
    integer_to_list(M*1000000000000+S*1000000+L).