Erlang 在两个mnesia表之间传输数据
我有两张桌子,柜台和柜台Erlang 在两个mnesia表之间传输数据,erlang,Erlang,我有两张桌子,柜台和柜台 -record(counter, {key, value}). -record(count, {key, value}). create() -> mnesia:create_schema([node()]), mnesia:start(), mnesia:create_table(counter, [{attributes, record_info(fields, counter)}, {
-record(counter, {key, value}).
-record(count, {key, value}).
create() ->
mnesia:create_schema([node()]),
mnesia:start(),
mnesia:create_table(counter, [{attributes, record_info(fields, counter)}, {disc_copies, [node()]}]),
mnesia:create_table(count, [{attributes, record_info(fields, count)}, {disc_copies, [node()]}]),
mnesia:stop().
但是当我试着运行这个函数时
backup()->
mnesia:transaction(fun() ->
Records = mnesia:select(counter, [{'_', [], ['$_']}]),
[ok = mnesia:write(count, Record, write) || Record <- Records]
end).
当我使用您的代码时:
mnesia:create_table(count, [{record_name, counter}, {attributes, record_info(fields, counter)}, {disc_copies, [node()]}]).
当我尝试运行model:reset()时,它会删除表计数和表计数器的数据
我的目标就是删除计数器的数据
这是reset()的代码
您正试图在计数表中写入计数器记录,这将导致错误。有两种方法可以做到这一点
mnesia:create_table(count, [{record_name, counter}, {attributes, record_info(fields, counter)}, {disc_copies, [node()]}]).
reset() ->
stop(),
destroy(),
create(),
start(),
{ok}.
destroy() ->
mnesia:start(),
mnesia:delete_table(counter),
mnesia:delete_table(person),
mnesia:stop(),
mnesia:delete_schema([node()]).
create() ->
mnesia:create_schema([node()]),
mnesia:start(),
mnesia:create_table(counter, [{attributes, record_info(fields, counter)}, {disc_copies, [node()]}]),
mnesia:create_table(person, [{attributes, record_info(fields, person)}, {disc_copies, [node()]}]),
mnesia:create_table(person_backup,[{disc_copies, [node()]},{attributes, record_info(fields, person)},
{record_name, person}]),
mnesia:stop().