I am having problems with the size of dets file.
> {ok,D1} = dets:open_file(sample_dets_file, [{type, set},{auto_save,3}]).
{ok,sample_dets_file}
> [dets:insert(D1,{{fid,X},"this is sample data"}) || X <- lists:seq(1,10000)].
> dets:info(D1).
[{type,set},
{keypos,1},
{size,10000},
{file_size,769748},
{filename,"sample_dets_file"}]
> [dets:delete(D1,{fid,X}) || X <- lists:seq(1,10000)].
> dets:info(D1).
[{type,set},
{keypos,1},
{size,0},
{file_size,770092},
{filename,"sample_dets_file"}]
After insert - {size,10000}, {file_size,769748}
After delete- {size,0}, {file_size,770092}.
The file size has not reduced even after table is empty. However when I execute delete_all_objects, file size returns to normal.
> dets:delete_all_objects(D1).
> dets:info(D1).
[{type,set},
{keypos,1},
{size,0},
{file_size,5464},
{filename,"sample_dets_file"}]
I could not understand what additionally i need to do along with delete operation so as to reduce the file_size. The problem is, since dets file_size is limited to 4gb, even if objects are deleted, I reach the size limit of dets file.
The dets implementation doesn't try to shrink the file when entries are deleted, except when you do delete_all_objects. To shrink the file manually, you have to create a new temporary dets file, copy all entries to the new file, remove the old file, and rename the temporary file to replace the old.