mnesia_schema patch

[Ulf Wiger]

The attached patch to mnesia_schema (mnesia-4.1.3) exports
the do_delete_table/1 function. This is symmetrical to the
already exported do_create_table/1.

The use of both is to be able to do something like the
following:

add_context(Context) ->
   mnesia_schema:schema_transaction(
      fun() ->
         case mnesia:read(context, Context, read) of
            [] ->
               mnesia:write(#context{id=Context}),
               lists:foreach(
                  fun({TabName, Opts}) ->
                     Cs = mnesia_schema:list2cs(
                             add_name(TabName, Opts)),
                     mnesia_schema:do_create_table(Cs)
                  end, sub_tables(Context));
            _ ->
               mnesia:abort({exists, Context})
      end).

remove_context(Context) ->
   mnesia_schema:schema_transaction(
      fun() ->
         case mnesia:read(context,Context, write) of
            [_] ->
               mnesia:delete(context,Context,write),
               lists:foreach(
                  fun({TabName,_}) ->
                     mnesia_schema:do_delete_table(TabName)
                  end, sub_tables(Context));
            [] ->
               mnesia:abort({not_found, Context})
      end).

...without totally messing up your database upon partial
failure.

/Uffe
-- 
Ulf Wiger, Senior Specialist,
   / / /   Architecture & Design of Carrier-Class Software
  / / /    Strategic Product & System Management
 / / /     Ericsson AB, Connectivity and Control Nodes
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> 	 do_delete_table/1,